Experts help with air trac!
I'm having problems with my air trac suspension. I've had problems with a driveline vibration for awhile now.
Here is the first place I read about ride height being a common cause of vibration. All of my driveline was worn out so I had it rebuilt. Both shafts had new slips welded in and all new u joints. It's a day cab with 186" wheelbase, so no carrier bearing.
I replaced the leveling valve and linkage, and set the ride height. It was way too low before. I also replaced the wear pads and roller bushings on the rear axle. Ran out of time and gas for the torch before doing the front. Not perfect, but totally different truck after this. Almost all better. I chalked up the little bit of remaining vibe to worn out suspension bushings. That was probably correct but not sure.
Then the frame cracked badly. I had it professionally repaired and it has held up well. But after that, vibration was worse.
Kept feeling vibe and then my clutch was way grabby and something didn't seem right. I had just had the clutch replaced around 8k miles ago. Did a visual check, trans about to fall out. The rear support was completely loose. Only 4 bolts going from trans to clutch housing. Only 3 on the bottom were tight. 5 have the heads busted off. Put in 2 missing bolts and tightened all the others. Replaced bolts for the rear support and got it tightened up all the way. Noticed that the output bearing in the tranny has some play. Vibe still there after securing trans.
Blew 2 air bags within a couple weeks of each other because the tops rusted and the bolts broke out. Bobtailed home each time to replace. All of the weight rested on the bag on the opposite side of course. This leads to where I'm at now.
The pedestals where the bags mount appear to be pushed down towards the ground. They are uneven. To get even close to the correct ride height, the bags are almost fully extended. There is 2.5" between the highest and the lowest pedestal measuring from the ground to the bottom of the pedestals. Even the one furthest off the ground seems too low. I can't tell exactly where the problem is. Do I need to replace all the u bolts and add shins? The rear axle seems to point upwards a good bit more than the front. It looks like this is intended with the way the brackets are made but not sure?
A couple interesting things about the vibe. I can drive out of it if I drive fast enough. If I go over bumps while coasting it will stop, also.
The truck is a 98 Pete 378 day cab, DDEC III Detroit, Eaton 15, 44k air trac, 46k Rockwell full locking rears, w/ 4.56 gears, 11R24.5's.
I can get pics if that will be helpful. Sorry for the novel, but I wanted to be thorough. Without the proper info, I know you won't be able to help! Hoping 379Longhood and Sledman will chime in. I'm really close to Sled in Lexington, NC.
Thank you in advance!
98 Pete 378 12.7,15spd,46k rears w/ full lockers