[mobile alignment]

The newest six wheel bogie vehicle since the GMC.  They know how to cut the bumps in half.




The Maintenance manual is very mis-leading on how to tighten the rear spindle nut.  The 25 ft-lbs is only the initial torque to seat the bearing & then it is to be loosen & re-torqued to finger tight or less.  Over torque of the spindle nut will lead to a very hot bearing very quickly.  I have seen the spindle shear off on several coaches that were torqued to the 25 ft-lbs level & left there (the wheel passed the coach as it slowed down).  Big $$$$$$ repair.Duane

But here's the exact instruction from X-7525:

"and hubs on spindle. Tighten castilated nut (figure 17) to 25-30 ft . lbs., back nut off one half turn and then finger tighten until cotter pin can be installed."

Assuming the spindle threads are 16 tpi, that's 1/2*1/16-1/6*1/16=0.021" axial clearance (plus whatever slop comes from grease interference, etc.);
I'd rather see <0.010" -- and even less with my disc brakes.  Many references I've seen recommend 0.001"-0.005", but I think anything <0.005"
is risky.JMHOKen Henderson

What about rear bearings and seals?

Checker had all the parts in stock and were cheaper than AutoZone. They carried Chicago Rawhide (CR) which is an old line US manufacturer. When you look closely at the inside bearings you see
"Mexico" on them!! The outside bearings are made in Germany. The outside cones and seals made in  USA.


The seals are Part No. 21771 and costs $3.89 each. (there is only one per wheel and it is on the rear)
Rear---National# 8974S,  C/R# 21771Denny Allen
SEAL UPDATE  (10/5/10)

Dave Lenzi found some are wrong and even if you have the correct part number on the Timken seal  you have a big chance it won't fit right.  They have two different seals using the same number.  The grease will leak out and there goes the bearing..GeneD

I think the jury's still out on the final verdict.  But for now, the surest check seems to be the 0.260" measurement Rob quoted from Dave.  That's the distance from the inner rim (the "sharp one") to the lip of the flexible seal.  In other words, perhaps easier to remember, 1/2 through the axial dimension of the metal seal, which is 0.500" KenH

Dave Lenzi gave me two manufacturers for the rear wheel seals that are OK. 
They are:  Chicago Rawhide-3857731 and SKF-21771.

I picked up one SKF from NAPA today and it is the correct seal.. GeneD


The inner cone (cup) is LM501310 , $3.89.
The inner bearing is LM501349 , $8.29.
The outer cone is BR15243, don't remember the cost.
The outer bearing is 15103-S, don't remember the cost. Emery Stora



    Modifying the bellows port adapter fitting on the ride height valve to accept compression fittings when the plastic fittings go bad.     Well I got mine finished and it works. I will try to explain. Some of what I think I have found out is that the early valve
connections were metal as shown in the maintenance manual. Page 4-21 of manual attached. No where in the parts or
maintenance manual have I found any pictures of the plastic connectors that I have had trouble with leaking and have not
found any replacements available to repair. It is my understanding that GM started putting the plastic connectors on the coaches in 1975 and that when they star leaking there is no replacement available for the Bellows port unless you buy a new leveling valve. We are not the first to have problems with the plastic valves. We may be the first to fix them with 3/8 to 1/4 compression fittings.
       Parts required.
        (2) 3/8 compression ferrule sleeves
        (2) 3/8 compression nuts
        2 inches of 3/8 copper tubing.
        (1) 3/8 to 1/4  reduction compression fitting.
        (1) little sleeve that goes inside the 1/4 inch tubing
    The first thing I did was remove the bellows port  adapter assembly from the body of the height control valve. It did not take much effort to break it loose. I had clamped the mounting bracket in a vise and used a medium crescent wrench to unscrew it. Once I had broken it loose I unscrewed it by hand. I caution you to be careful and not loose the screen. After removing the adapter I took it to a machine shop and machined the end where the plastic fitting attached. I machined the inside to match a 3/8 female flair fitting. All I had to do was put it in a lath and drill and ream the port end. I did not drill it quite as deep as a standard  fitting. I tried to not go any deeper than the existing depth of the 1/4 inch hole that was there for the plastic
fitting. After drilling and reaming the 3/8 diameter I took a 90 degree counter sink and put a very light chamfer on the front edge for the flair fitting that slides on the tube to seat against. This completed the required repair of the adapter fitting. The compression nut that is going to screw on the adapter fitting needs to be machined so that it will not bottom out on the shoulder
of the adapter fitting.  The nut I had was .470 long . I machined .070 off of the threaded end. If you don't do this the compression nut will bottom out on the shoulder before the flair is compressed enough to tighten down on the tubing. One of the attached pictures shows the different lengths of the 3/8 compression nuts. This completes all of the machining required for this modification. The rest is just assembly.

    Install the adapter assembly in the valve body. Attach the 3/8 copper tube to the adapter assembly using the modified compression nut. Then to the other end of the copper tube attach the 3/8 to 1/4 reduction compression fitting. When you attach the 1/4 inch air line to this fitting be sure and install the little sleeve inside the tube to aid in sealing. This fitting leaked air until I installed the sleeve.     Andy you said, "I need two as I broke both yellow and red". On my system the fitting that the red line goes into will take a1/8 pipe thread. You can buy a 1/8 pipe thread to 1/4 compression fitting that you can screw right into the air inlet port fitting. This fitting does not require all the modification the bellows port does. See all the pictures attached. Charles Wersal
 I believe this is the adapter you are looking for.  I had to replace mine on my '76 PB.  It was on top of the three way valves in our valve cluster. I was able to purchase them from a local Parker/Skinner distributor.  About $10 ea.! It took a lot of effort to find this part because the part number on the valve is not used.  I ended up sending them a picture of the valve to get them to believe it was one of their valves.

After all my effort in finding a source I found that CINNABAR has the adapters in stainless steel.  Learned from reviewing old publications of their's.Below is a copy of part of my email from Parker.

>The adapter used on this valve is a 1/8 PTF x 1/2 UNF.  Our P/N is J21-001.
>This item is not normally sold individually, but we I spoke with our
>customer service manager and we will allow a one time purchase on this
>item.  Please contact your local distributor at
>under distributors for P&D if you wish to purchase this item from us.
>Or, if you prefer, you have the basic info on the adapter and can source it
>elsewhere.The valve you have is an old valve we manufactured for GM.
Todd Elson

Air Bag Extenders and Four Baggers
There is a new article in the Cinnabar GMC news (Dec98) that says:

Click for Detail Picture by Mike Finnicum
Air bag extenders:

         makes the ride softer but increases the wallow side-to-side
         do not extend bag life

An earlier article  in Cinnagbar News Sept. 98 , vol 17 , talks about four baggers.

Four baggers:
         stiffen the ride (reduce the wallow)

         eliminate the preferred bogie action
         reduce the leveling action
         raise the pressure required
         increase the bending load on the center arm

Owners love all of these for different reasons.  Be sure to read the literature to make your own decision .gene

I installed the four-air bag system during the GMCMI Myrtle Beach Rally in March 1995 at the same time as I installed Leigh's six-wheel disc brake system.  As I said the other day in response to an e-mail message asking about the wear of carbon metallic brake pads, I have over 40,000 miles experience with the system.  Compared to the original, I notice a definite increase in the fore-to-aft dampening of the ride, and much greater stability in truck-rutted asphalt paving.  I can't even feel the difference when the coach drifts over the joint between the roadway and paved shoulders, and have demonstrated such with folded arms not even holding onto the steering wheel at the time.  When I drift onto an unpaved shoulder, there is no problem recovering.  I haven't met anyone yet, without Leigh's system, who feels very comfortable in running off the edge of the road.

Leigh also claims that the rear-rear axel spring rate is doubled to around 815 psi, compared to the original.  This in turn, makes the brakes on the axle able to exert more stopping ability prior to lock-up (which I've never experienced thus far).

If you already haven't heard it in a few previous e-mail messages, the original air bags are rumored soon to be in short supply, as the molds used to make them are supposedly near the end of their life.  Then what are you going to do??????

I would encourage any doubting Thomas's to go with Leigh during the GMCMI rally's, when he routinely takes people for a demonstration ride.  You can't believe the stability his coach demonstrates.   Paul
My "light weight" 23' tips the scales at 5800 lbs on the rear axle with all tanks empty. I'm guessing the left tandems carry about 3200 of that (genset and kitchen on that side).That's 1600 lbs per left rear tire with O.E. suspension, which distributes the weight more or less equally within each tandem. But it looked to me that the 4-bag conversion would result in the momentary transfer of the entire weight on one side back and forth between the tires in that tandem, and our load range E tires are rated to only 2680 lbs.Richard



> There are no time limits on the recall.  Larger pins were introduced  at TZE0X4V101024 and coaches earlier than this Vin number are subject to recall.

It should be noted, however, that the recall is for rear hubs and spindles, not bogie arms. My spindles and hubs were replaced as part of the recall, but I still have 1-1/4" bogie pins. Rick

The Recall is 74-C-07 and is dated May, 1974.It covers all 1973 and 1974 GMC Motor Homes shipped prior to May 1,1974.

It states that "the rear suspension outer wheel bearings may fail and a rear wheel coul separate from the vehicle and cause property damage or personal injury."The recall would replace all four rear spindles, all 4 brake assemblies, hub and drum assemblies, inner bearings, outer cone and roller assemblies, washers, nuts, cotter pins, inner and outer dust caps, etc.

In the Recall it states:
"Dealers are to service all vehicles subject to this campaign regardless of the mileage, age of vehicle, or owner."And, as I said in an earlier message, there is no time limits on recalls mandated under the National Traffic and Motor VehicleSafety Act.-EMERY
Not to belabor what is probably an old topic to many owners, but rather for the benefit of new owners or subscribers, I just had a nice chat with Wes Caughlan and he outlined the basics of what to look for in terms of whether or not this recall has been done on a coach.

He indicated that even if the S/N records show it as having been done, the records could be wrong. The four things he said to check that will be about 99% positive from easy to difficult are:

1. The wheel centering protrusion on the hub should have eight rather than four notches.
I talked to Ivan at Cinabarr to find out how to see if mine had been done  I sent the photo to Toby to help him. The easy way to tell if it has been done is to remove the hubcap and look at the shoulder that the wheel centers on. If it has 4 notches equally space around this shoulder it has not been replaced. If there are 8 notches around this shoulder it has been replaced or is the later release. I got this info direct from Ivan at Cinnabar. I am attaching a picture to help clarify sholder notch. Charles
2. The inner dust cover (not the outer decorative cover, just before you get to the axle/bearing nut) should be 2-1/2" in diameter.

3. The axle/bearing nut should be 1-1/4" rather than the original 1-1/16" (can be measured with a socket).

4. The spindle and backing plate hole should be 2-1/4" rather than the 1-7/8" of the original.

And in case anybody else is interested, the full set of service bulletins, all back issues of the GMC Motorhome News, and a year's subscription will set you back $154.00 plus shipping. At today's prices
here in Redlands of $2.259 for gas, it's about one round trip to Las Vegas. I believe it to be money well spent.Carry on!Toby Maki

Another variable from coach to coach is the wear on the rear pins. I have a coach here that had a mind of its own according to the owner. The rear pins were very loose so the coach was riding on four casters back there. The easiest/best way to check and get a repeatable measurement is:  Support the coach under the rear suspension mounting bracket at approximatly the correct ride height. Loosen all lug nuts on both wheels. Release all air from the air bag. Jack up the suspension arm only--just enough to get the wheel off.
With a piece of wood, standing on end, support the end of the control arm at the spindle end. Move the spindle end of the arm towards and away from the frame and measure the total movement with a tape measure. GM Service Bulletin #75-TM-4 states 1/8" is maximum.

A big job to fix but this coach was about 1/2" movement on three of the four wheels. I had to bush the inboard end of the bracket, replace pins, bushings and top hats. Denny

BOGIE PINS should be greased about every 1000 miles or every trip.  They should be greased with the weight off of the bogie as described above.  Raise the unloaded wheels with a shovel or pick to remove the weight off of the pin while applying the grease.

Build Your Own Dual Zerk Bogie Greasers

A tool has been made that will make sure the grease gets to the rear of the bogie pins.  Click on this URL.

You can buy these already made.  Look here to find the vendors, use (Ctrl-F) to search for Bogie
Also sold by Jim Kanomata and Jim bounds

They are also listed on Ebay.  Go to:
then search for "Bogie easy" and you will find the listing

  The bogey pin is a tube with a zerk threaded into the end cover. Ithas two holes in it, an inboard hole close to the frame rail and an outboard hole, both designed to inject grease in the two bushings oneach pin. If you use the single factory zerk, the grease tends to smoosh out one end, taking the path of least resistance, and not getto the bushing at the other end.

There are two possible solutions to that problem. The first is to movethe bogey around while you are injecting grease such that you work the grease into both ends. That's what you use the shovel for. Jack up the bogey frame, let the air out of the suspension, and then use a shovel as a lifting tool under the tire. Move the tire around until you canget the grease to smoosh out both inboard and outboard ends of the
bogey pin bushings.

The better solution is to remove the zerk and replace it with a bogey greaser. The greaser that uses two zerks is the improvement. The way
it goes together, one zerk will inject grease right under the fitting, and the other zerk will inject grease out the end of the tube. The flare or collar on the end of the tube keeps the two separate. That way, one zerk will force the grease out one grease hole, and the otherzerk will force grease out the other hole. That keeps you from needing to jack it up and take the weight off the tire.

Those of us who have '73 coaches with the original pins can't use this trick, though. Our grease holes only go halfway through the pin to a
single hole in the middle. (I didn't find this out until I'd installed greasers, and I kept wondering why I was having to shorten the tubes!)
Rather than jack up the back of my coach, I just put my wood blocks under the bogey frames that I use for winter storage, let the air out
of the bages, and then I can wiggle the tires back and forth even without a shovel. A 4x6 timber, standing with the tall dimension vertial, will keep the coach high enough for storage.


Carry these for emergencies, and  this is what they look like , and where to find them

Here is a photo explanation

I would not have believed it if I had not seen it with my own eyes.   I did have one bag that scared me a bit and we let the air back out and made sure the coach was high enough.   You have to have the wheels able to go all the way down.  The more room the bag has the better it can assume its shape.

When I did my air bags several years ago, I put the cones on and fitted a Shrader valve on the end of the bag.  I put one end on the ground and started adding air slowly while pushing down.  The cones came in against the bag just the way they were on the coach.  Just don't put any extra air in or they will pop out again. Doesn't seem possible, but it works.Gene Dotson

Since it is not possible to determine the condition of the airbag by looking at the rubber covering:
see the discussion below

you might want to use the age-of-the-bag, to make your decision to replace the airbag.   I determined to post the Firestone info on this so we don't loose it again, and again, and again. ( thanks to harperJ for finding the link again in 2005;<)

You might also want to read the condition information from  the horses mouth (does this date me ?),Firestone.   This is better than information from the other end of the horse ;>)

Looks like this info also applies to 4 baggers
as always, there is no definite cutoff date or criteria for this maintenance operation. good luck gene

I know of 3 separate failures this year, of the short nipple that goes between the cutoff valve and the air bag.  The nipple used by most of these assemblies is brass.  This would seem to be the quality thing to use here since it will not rust or corrode.  However the combination of assembly weight, lots of motion and thin material in the nipple leads to the cracking of this nipple.

The answer to this problem is to replace the nipple with a steel (stainless for Manny) nipple.  It appears prudent to replace the nipple NOW before it breaks at an inopportune time and location.  One of the stricken owners was looking for an air leak, when the nipple broke and the assembly shot into the wheel well, leaving a very short piece for extraction in the Air Bag.  He was very glad his head was not in the wheel well when this exploded.....

Always put jacks, blocks, jack stands, (everything you can find) under the frame and bogies of the GMC when ever you work on the rear of the GMC, and I release the air pressure to the bags.  There is a 8,000 lb weight and a 120 lb pressure vessel in there, that could fall at any time , and we all know a GMC gets lower than a Snake's belly when it falls....... Yikes gene


A while back, I asked if anyone knew the correct size for the "O" ring used to seal the adapter piece to the air bag and didn't get a response.  After trying serveral sizes, it appears the correct "O" ring has a 7/8" ID, a 1 1/16" OD and a 3/32" diameter.Jim Moore

Yes, the fitting that the air line is connected to is threaded into another fitting that takes the mounting nut.  If you "double nut" that thread with 2 nuts and back it out of the air bag itself, you will find dwn in the "female" hole a shoulde that has a rubber "O" ring on it.  Admittedly, Firestone said they installed the fitting dry with an air tool which sometimes tears the seal.  Take it out and inspect it.  If it is deformed or torn, take it to your local hardware store and get a replacemnt.  We put just a light film of RTV on the seal to act as a lubricant as the fitting seats home then when t cures I think it will help to seal everything.  This is a common problem if you have a leak and cannot find it anywhere.,Jim Bounds

Mc Master is king-- folllowing a link from Bob Burkitt, to John shotwell,  here are the Mc Master numbers for the stainless air bag nuts

98438A036       1 Pack  410 Stainless Stl External-tooth Lock Washer, 3/4" Screw Sz, .768" Id, 1.26" Od, .047" Min Thickness

91847A555       1 Pack  18-8 Stainless Steel Hex Thin (jam) Nut, 3/4"-16 Screw Size, 1-1/8" Width, 27/64" Height

John Shotwell

Air bag price   $219.00   This price sheet does not list alum cones.

Gateway Motor Home Co.  High Ridge,Mo
Questions   1-636-677-2277
Order line  1-800-654-0374

A number of years ago Wes Caughlan reported to a GMC Western State Roundup, that one should never install an Air Bag w/o first testing it for air leaks.  He stated that 35 % of new airbags from a warehouse (about 1990) was tested & 35% had leaks.  Warranty is for only 90 days & should be tested as soon as received & before installation.  The way to test an air bag is to install a schrader valve (1/4" pipe thread) into the end using "Pipe Sealant w/Teflon" & then pump the bag up to 40 PSI &
submerge it under water to find leaks. Works For MeDuane Simmons

HOT DOG AIR BAGS can be prevented by rotating the bag 180 degrees (top to bottom) once a year.  This also keeps the threads clean so the bag is easily replaced in case of failure.  The air bags tend to take a set in the inflated condition so it is also helpful to rest the coach on a block between the wheels and let the air out of the bags when the coach is in storage.

TREATING THE BAGS with brake fluid or rubber treatments is not recommended.  Cracking of the outside rubber does not indicate a bad bag.  There does not seem to be a good indicator of a tired bag. gene

Does everyone know that the GMC airbags were originally made to serve as supports for laboratory benches so as to prevent vibrations?  GM adapted them for the motorhome.  Their construction is actually a fabric bag that has a rubber coating.  The coating does check (just like tires exposed to the sun and weather).  I suppose you could use a rubber preservative or coating but be careful that you don't use one that will deteriorate the rubber. (No petroleum based substances).  Also be sure you do not leave a sticky residue as that would trap sand particles where the bags fold on the cones and possible leaks will result.  There are some tire dressings that contain polyglycols that won't harm rubber.  I don't use a coating.  I do, from time to time, inflate the bags all the way and then scrub them well with a brush and car wash soap to get off the road oil and dirt.  The fender skirt ("T" or triangle or the full flare skirts) shades the air bags.  If you don't have them you should consider putting them on. Emery


Put a Shraeder valve into the bag and inflate it with shop air or whatever.    Put the coach weight on it. Now the bag won't turn as you remove the nut.  Once the nut is off, deflate and carry on.

Shraeder valves are readily available at auto or hardware stores. Usually  called tank valves. You want 1/4" pipe thread so a 1/8" to 1/4" bushing may  also be needed.Denny Allen



Firestone recommends the plastic cones be used only if their entire base is supported.  The GMC only supports the center of the cone.  Aluminum cones can be used either way.  The two types of cones are interchangeable using the same bag.

There have been reports of the plastic cone disintegrating resulting in damage to nearby objects, so far, the objects have been inanimate.  I would be very concerned about putting my face close to the plastic cones when the bag is under pressure.

Here is an example:
I can attest to the exploding plastic cones. When mine came apart I found pieces all the way up on the shop roof. I'd had my face in that wheel well just seconds before. So I could have been hurt if the timing had been just a little different.

These exploding cones may well be isolated instances but then so is getting struck by lightning.So be aware and be careful Dave Mumert

I read in an old Cinnabar newsletter that there are black and gray plastic cones. The black ones are the ones that break, according to Wes.     Kelvin
Several years ago, I had my 77PB in to Buskirk's for rear wheel alignment.  Clarence noticed I had plastic cones and changed them to aluminum without charge.Said the plastic were not dependable or safe. That was good enough advice for me to recommend changing all plastic cones to aluminum. Just my opinion.Andy

The plastic cones are typically black in color and if you tap them lightly when they are out make very little sound.  The early alum cones are not painted, the later cones are power coated in black.  Both of these cones make a nice ringing sound when tapped with a hammer if you hang them from a string. J.R. Wright
The plastic cones are very dangerous & should be replaced with the Aluminum cones.  Yes I have seen the Plastic cones let go/blow apart & do not want to be around when it happens again.  The Aluminum Cones can be Identified by having radial
supports/ribs extending from the center of the cone to the outer surface of the cone as viewed into the end of the cone while installed in the bag.  Beware when replacing the cones, there are two different configurations.  One cone has a large hole in it (air filling end) & the other cone has a small hole for the non filling end.....don't cross then up. Duane

Emergency Air Bag substitute

This Rod is used to replace a leaking air bag in an emergency to get you home or to a repair location.  To insert the rod the GMC must be jacked up and the old air bag removed.  This rod is then inserted in place of the air pag to keep the rear suspension level.  With this rod installed, there is no suspension for this set of wheels, so the driver should drive carefully and not drive any farther than necessary to replace the bad air bag.

The BagRod is made up from a 3/4 inch threaded rod with a 3/4inch pipe over it and two washers.

The dimensions are :

3/4 inch Threaded Rod   18 inches long
two 3/4 inch nuts
3/4 inch gal. pipe 15 inches long.
two each 2 inch washers


GMC International News Letter # 18

A 4"X 4" piece of wood cut to the length of 13.5" with a hole in the center
of each end to accept a  5/8" X 5" lag bolt has been used.

A 1 1/2" iron pipe 13.5" long and used a 5/8" threaded rod 16" long with a
nut and lock washer at each end.

GMC Newsletter # 37

A 3/4" threaded rod 18 1/4" long and 2 nuts threaded onto each end of the
rod. Distance between bogie arms 13.5"

Ragusa sells a temporary replacement airbag rod, complete with rubber pads
and hardware for $38.00.(RV-08)


Raising the GMC on jacks is problematical:

     The frame often gets bent
     The Jacks slip
     The fame gets twisted
     You need a really big jack
     It is really not very safe under a GMC on jack stands
     It is almost impossible on dirt or gravel.

Stacked Blocks Ramps and front ramps
Plans for Ramps
Hooks, Ramps N Stuff
Jack Pad for the GMC Front

The best way to work on the bottom of the GMC for us PWOP's . ( People With Out Pits) is to build ramps of stacked 2 X 8 boards.  Mine are 4 high which will raise the GMC something less than 8 inches  which  with the 4 inches the air bags will raise, allows you to get under the rig safely.   You can then place the jack stands under the frame for added safety  and use the old reliable 6 inch by 8 inch block under the bogie support.

Using this method you can :
     Drain the gas tanks ( raise the driver side)
     Drop the gas tanks for hose replacement
     Repair the Black tank
     Replace the Iso pads on the frame
     Add the booster electric fuel pump.
     Drop the radiator for recoreing
     Add the Macerator  poop pump
     etc, etc

Lots of good stuff to do under the GMC  for us  pit-less folks.

It has come to my attention that not all of us have a Hook so that we can use a small bottle jack to raise the rear end of our GMC coaches without removing the T divider.   The shop manual says to use a one inch board to raise both bogies and one GMCer uses a spring leaf.  Florence Or. was not progressive enough for me to find a spring leaf the correct size so I used a steel plate.
Several years ago when I bought a new screen door from Alex Birch he sent me several drawings of improvements I could make on the GMC.One was a bar to go under the bogies 11 X 3 X 1/4 inches flat bar stock.I made a couple, but I didn't like them because they would bend.That's when I came up with the idea of a spring leaf(68 Toro) and it works great.The arms with 1 1/4 pins are closer to the bogie than the 1 1/2 pins so I used a section of a spring leaf close to the eye where it's tapered.The longer you make them the harder they are to put in and 11 inches is long enough.HTH  Milt

Click For larger picturel There are at least four sources for the Hook.  

Here are some links to hooks (1/30/08)
Paul Z. Bennett, 2400  Blossom St., Columbia SC 29205, Phone:
                             803-799-4323. Email:
Wayne Alumbaugh, has a stepped hook for flat tires.



I like the one shown (Bebe)since there is a lip around the area where the jack shaft makes contact.  This lip will help keep the jack from slipping. The Hook attaches just like the Mondo Jack supplied with the GMC.  The big difference is now you can use a small 4 ton bottle jack to raise the GMC without removing the fender skirts.  It has been said that there is nothing lower than a GMC with a flat tire.
Click for Detail The plate is slipped through a slot above the hook in the bogie pivot.   The plate will extend far enough on each side of the pivot to hold up both bogie arms.   After the plate is in place jack up enough to take the slack out between the plate and the arms.  Then let the air out of the air bag on this side.  Now when you jack both wheels come up right away .   This will reduce the height you have to raise the coach.

Here is a picture of where the plate goes

This is a good time to grease the bogie pins, rotate the wheels, check the brake linings, adjust the brakes, etc.

This combination of jack, hook, and plate make a very efficient way to change a flat.

 Four Air Bag Rear Suspension
 Rear Suspension Rebuild
  Air Tank Rebuild
 Air Leveling System Upgrade

String Alignment


  I just had a fixture made to do this very thing and used it for the first time just yesterday.  My wife hit a bridge curb on its maiden voyage on the way to the Mobile convention in 2004.  Blew two new tires and broke a brand new Alcoa wheel and bent the crap out of the rear arm.  Gary & Kara Kosier came along, bless their hearts, and had a spare for the unbent arm.  Limped to the rally by wearing a near full tread spare to the cords in a little over 100 miles on the bent arm.  We put the steel wheel spare on the hub backwards, and I used a jack to "temporarily" bend the arm back into position by eyeball per suggestion by AlexSirum.  I cringed knowing the loads that the brand new bearings were seeing.  That was four years ago.

The bushings in the front arm badly needed replacement, so before putting things back together, I thought those arms really should be straightened, so I had this fixture built.  Turns out the arm straightened with a jack was already perfect.  My eyeballs must have been better four years ago than they are now, because it was perfect.  The other arm was just a tweak in, less than a half degree.  I twisted both of them 1 1/2 degrees so fewer shims were required, plus I wanted to use this expensive fixture for SOMEthing!  It has the capability to twist (seldom needed) and bend in/out.

Jim Kanomata is going to add the fixture to his collection when we see each other at Delaware.  The whole thing can be packed in a box 31"x10"x8" and weights 87lbs according to our bathroom scales, which MUST read high based on what it tells me I weigh.  So it can be shipped UPS in an emergency, but will probably cost $50+ each way to do so.  Plus as someone pointed out, the whole thing needs to be off the coach which is the better part of a day job.  If I were going to build another, there are a few minor changes I would make, but all in all it worked out well.

Here is a variation on the string alignment using laser Pointers (1/3/7)

By Darcy Moses

By Egon Elssner

This technique has been talked about for years.  At least one major shop uses this for alignment and at a minimum it is great to see how good your alignment is.

Front end Alignment
Rear end Alignment
Centering Steering Wheel

Front end Alignment Settings 3/20/05

Caster Camber L.H. Camber R.H. Toe In/Out LINKS TO SOURCES

Factory Alignment  +2 +3/4  +1/2  - 1/8" (Toe Out)

(anonymous author) +1 0 -1/4 0  (Toe In) BDUB

Caspro +2 1/2 to # 1/2 0 to +1/4
+ 1/8 (NOT negative)  CASPRO

Dave Lenzi +2 1/2  -1/2 -1 - 0  (+ or - 1/16) LENZI

Jim Bounds
+2 1/2

+3LH +3.5 RH
1/32 IN

john harper


  "Metropolitan Elroy" mobile alignment?

Pick up front end to clear tires from ground. Rotate front tires, spray white paint all the way around, covering a flat spot (off tread cuts). Clamp awl or ice pick to your *heavy* jack stand. Use point to scribe a narrow line in the white paint.

Put the beast back on the ground, measure lateral distance of scribed lines at front extreme of tires with tape measure (2 warm bodies required). Measure as close as you can get to back extreme of front tire. Chalk on concrete or use scratch pad to "correct" your rear lateral measure to full extent of tire, i.e., you measured 3/32", would the full distance be equivalent to 1/8"?

Twiddle toe adjustment, move beast forward and backward to let changes "settle out", re-measure. Repeat until satisfied, or tired.

A laser alignment rack is a *lot* quicker, particularly for interacting castor/camber, but not much more accurate.

Camber takes a lot more words, castor even more words, but just a plumb bob, a bunch of string, some dexterity, and patience.

Kid hates it when I quote from a 50's Nipponese DIY bicycle assembly manual,"Assembly of this bicycle requires great tranquility of spirit".
Walt Taylor

Ride Height Adjustment

Chuck Aulgur

The following procedure is what I have found that gave me the best
1.  Adjust tire pressure to the correct level that you will be using when driving your coach.
2.  Find a very level spot to park your coach on.
3.  Jack up the front end and remove the wheels.
4.  Place jacks at each end of the front crossmember and adjust front height of  coach to the specified ride height.
5.  Drop the pressure in the rear air bags, then set the air system controls to travel and let it raise the coach to is' t current set ride height.
6.  Measure the rear ride height  and if not within specifications, adjust the levers on the respective ride height control valve.  You may have to modify the valve mounting holes slightly if the arm adjustment is
not sufficient to obtain the proper height.
7.  Repeat steps 5 and 6 until the correct rear ride height is obtained, then do not make any more adjustment to the rear height controls.
8.  Raise the front of the coach and remount the front wheels.
9.  Drive the coach forward at least 10 feet and them back up to the original location and measure the front ride height.  I find it best to drive over a 2x4 or something in this forward and backward travel to cause the front suspension to flex.
10.  Measure the front ride height and if not within specifications, jack up the front  end and make the necessary adjustments to the respective torsion bar adjustment screws, after they have been unloaded with a proper tool.  Be very careful as the load required to unload the adjustment screws is tremendous, and can bend or break the unloading tool if it is not of sufficient strength.  If full adjustment of the screws
are not sufficient to obtain the proper ride height, you may need to change the pork chops to ones with a different angle setting, or change to different torsion bars, or remove a few hundred pounds of tools and
spare parts from the coach.
 11.  Lower the front end and repeat steps 9 and 10 until the correct
ride height is obtained.

This procedure is what works for me. Chuck Aulgur
Approx. 6 turns of the height adjustment screw will give a 1" front adjustment. Duane

Torsion Bar tool

"Would you send me the dimensions (or drawings with measurements) of that tool? Do you know the NAPA part number for the U bolt?
For the drawing see: (Kelvin)

For a picture see: (kelvin)

While searching again for these pictures I found this one:

It appears Blaine had already invented; the tool using a u-bolt.  I don't know if he still sells this or not.  I got the idea to use a u-bolt from Larry W in a recent thread, picture at:

The NAPA part number is 650-4049.  This u-bolt is for mounting leaf springs.  It has a round shape (vs. square), is Grade 5, 5/8"; rod, inside width of  3.5";, 8.5"; long.  (this is longer than necessary but is the shortest u-bolt with the 3.5" inside dimension.)  This 3.5" inside width appears to be the minimum that will work.

On the net/forum we had some discussion about the length of the locating pin on the u-bolt:
The drawing for the factory tool shows the pin length as 0.850 from the top of the 5/8" bar. That's only 1/8". With a U-bolt with a curved section vs the factory bar that is flat, I decided to give myself a bit more. Larry W. welded on a 1" long piece. I decided to go long and cut down if necessary as you can't cut it longer. So mine is 1-1/2" which is way too long but for now it works for me. The diameter of this is 1/2" and it fit&#8217;s the hole just fine.  The pork-chop on the LH side of the coach is further down than I can reach through the hole with my little finger. I don't know about the RH side. I do fully agree with your comment that some cut-down may be necessary. Now that I can try it I will be able to determine just how long it should be. This is still somewhat of a work in progress. I'm going to be replacing the nuts and washers that came with the U-bolt with flanged nuts as it is a PITA to fiddle with the washer and nut getting it on.

The 1-1/2" square steel is 1018 and I made it 6&#8221; instead of 5.5&#8221; just to give myself some extra room, 5.5 long would work.  A friend with a tool and die shop offered to give me the chunk of 1018 and he also put in the center hole and tapped it 3/4"-16 as I did not have this size tap.  The most difficult part of the job was turning down the 3/4" bolt and putting the half round end on it.  Fortunately I had a lathe form cutting tool that worked OK for this.

The center bolt is from McMaster Carr and is the longest Grade 8 fine full thread bolt they have in 3/4&#8221;,  McMaster Carr #92620A881 (SteveS)
Nice summary  Steve
the only one you missed is made by Tony.  I am not sure he is still making these, he was hard to contact ( someone was trying a couple of months ago).  Maybe someone will tell us if he is still making these

Thomas  317 After-market Compressor

These were available from Scott Nehoda

Click for Detail The compressor is mounted in the same location as the original Dana, i.e. tucked under the air manifold / solenoid valve assembly. You have to drill 2 new holes in the sheetmetal tray to mount the Thomas.

In this installation the compressor's air outlet port is connected to an in-line filter/water separator via a coil of copper tubing. This has proven to be very effective in getting the moisture to condense out and collect in the bowl of the filter, rather than in the air tank as in the O.E. setup. I've also incorporated the rest of the Cinnebar upgrade incl. check valve.

Electrical hook-up is identical to the Dana - one lead for +12V and one for GND. Maximum current draw after initial start-up transient is 18 amps. (This would be when working at its maximum rated pressure of 150 psi.) The O.E. wiring circuit, which supplies the Dana via 14 gauge wire and a 30 amp circuit breaker, would probably be adequate but I have followed the advice of others who have recommended heavier gauge wiring and a separate relay even for the Dana, in order to minimize voltage drop over the long wire path from the start battery.