Follow the suspension repair and alignment on this coach
This coach was recently purchased by the new owners, a 76/97 Explorer renovated 23′ rear bath Birchaven. It was purchased by a recently retired GM exec. who had always heard how well the GMC coach handled, they wanted a “super SUV” to take them to see family around the country and be their mode of transport doing the things they have always wanted to do but had to stay at work. Very disappointed on driving, Larry had to hang onto the wheel full time and the bumpy wiggling ride was much less than enjoyable.
Coach road test:
We did a quick inspection of the rear suspension, the RR boggy wheel was visible pointing east while the coach traveled north, not a normal situation! We found slightly loose bearings and decided to go no further with this exam. I drove the coach home that night (4 miles) and found indeed that it drove like a brick. Hitting a bump in the road produced an oscillating vibration for over 5 seconds — Wow, never felt that before and there was some wander (play) in the steering wheel. Man, there is some trouble in river city here Batman! The power curve was very sluggish at the lower RPM range as well.
Hard component inspection:
There is most definitely some component wear out in the front suspension of this coach. After the road test, a complete mechanical inspection of the entire frame & suspension is made. No use to go through the trouble of alignment if there are loose steering components
We pulled the coach off the ground and went at the rear suspension first. The wrong shocks , these “limited edition” Monroe shocks must have come from Dr. Marvin Monroe on the Simpson’s. These are the wrong shocks. Limited means you take them off as soon as you put them on because they are charges backward for our coach. The geometry of the rear suspension uses the shock in the expansion stroke as opposed to the compression stroke as every other vehicle does. Sure these shocks fit but they work backward, no wonder we rode a wave when a bump was hit! The customer agreed that we should pull the drums, check the wheel bearings & races, repack them and install new seals so off the drums came. A good thing in that we found 2 of the 4 wheel cylinders leaking with one actually missing the outer boot. The shoes were not contaminated so we popped in new (not rebuilt) slaves, repacked the good bearings, replaced the inner seals and reinstalled and adjusted the rear bearings. The RR tire was chewed up on the inside (towed out) so we replaced the 2 right side rear tires and the 2 front tires. Interesting, the 2 front tires were brand new but they were the larger diameter 235/85 size while the rears were the standard size 225/75. This is probably why the “giddy up” off the line was slow, the coach is a 76 but has a 403 motor in it – most odd.
Next we headed up front and wow did we find something! The RF bearing had way too much movement ( actually any would be too much) but this one was rather extreme. In pulling off the knuckle and separating the hub and knuckle, we found both bearing surfaces were “cone” shaped. Print the drawing and follow me (no, I’m not Picasso!). With the wheel on the ground, the upward pressure created pressure at the top of the outer bearing and the bottom of the inner one, if the bearing gets loose, it will beat its way to open the tolerance in the hub and knuckle in this area
BTW, for you GMC netters, as you move the wheel out (space it out), this pressure gets intense and will, or should I say must, prematurely create this condition. Don’t look at me I didn’t write the laws of physics!
I exaggerated the second drawing but the hub was cone shaped to the inside and the knuckle was opened up to the outside. A rebuilt hub and knuckle along with a new bearing and seal were installed. Larry said since we did one side we may as well replace the driver side front bearing so “a pullin” we went. A good thing again, we found that the knuckle pulled off the hub by hand and easily. No good, the front bearing assy. is an interference fit and you must press them apart and together. This was probably due to use and not any unusual problem but left to its own could have caused trouble sooner or later. A rebuilt knuckle, bearing and seals were installed there.
The brakes were bleed and the babies new shoes were installed and this morning we are ready to check the alignment. I expect to find the rear swing arm grossly out (toe). BTW, we also found a ripped steering shaft CV boot but I want to get through the alignment before we stop to repair that. It will not effect the alignment outcome & I wanna get all wheels front and center now!
So, you are where we are. Come back later today & I’ll post our progress on the alignment procedure. Boy, sure hope I didn’t make a mistake letting you guys in on the job while in progress, this is where the rubber meets the road (metaphorically speaking) on doing the job. Wish us luck!
OK, boys and girls, here we go: The alignment machine is now hooked up and one look at the rear wheels shows what we already knew , the top screen and Nathans hand show the 2 rear wheels grossly toed out. The Camber is a little in but still in tolerance, so now we’re of “toe tapping”. Now if you promise not to cry, we’ll let you watch this! First we place a 6 tome ram behind the swing arm. Some say that you can’t push on the frame, this means they have never done an alignment and seen how easy the arms bend. Look, they were meant to flex (and BTW for you netters talking about the true track gizmos they must flex to keep pressure from the frame, attachment bolts as well as to keep the tires from scuffing off their tread) and all you need to do is push them past their flex point and they bend very easily. The RR wheel needed 16 pumps past center to get a proper toe readout. The computer alignment machine is used to calibrate the push and show the results . One down and now the driver side to go. It wasn’t nearly as bad as the pass. side but it was still out of tolerance. Hooo-Ha, snake eyes! Rear toe is in. The camber in is more a factor of an old frame than alignment trouble and in that they are within tolerance and it would take hours of shimming, I’ll buy theses specs for a dollar! Now for the front!
Survey says — not bad but its the small things that make the difference and since I spent $12,000 to have the machine to allow me to “dial it in”, we’re gonna make it better. Both cambers are in a bit (in tolerance but not good enough for me) and we have a slight forward caster (makes steering a bit harder). The toe screen shows the steering wheel is cocked to the right & its pigeon toed a bit. “Diver down”, Nathan grabs his wrenches and gets into his work! A little tweek here, a few well chosen words there and jackpot double snakeeyes! Camber is right on, I like to have as much caster as I can get but hey, its hard to argue with perfect! Now we attack front toe, Turning the tie rods we adjusted the toe than we kick the tires to center the toe and them Vwa-la Toe is found! Now comes replacing the torn steering CV boot, there goes Nathan again, man are you sure you can get out of there! Well, he got the steering shaft out These boots really stink, they split apart for no apparent reason and they are a @#$% to get out and replace the cheap part, what a bummer!