truck problems

[orion4096]

I've been ignoring some problems with my truck (silverado duramax allison 6speed automatic 2500hd) where shifting into gear and occasionally shifting on the road results in a clunk and the truck jolts. Driving home from work yesterday it felt like the back end was all over the place above 25 mph and it would step out during turns even at "normal" speeds. I'm hoping it's just the driveshaft/u-joints and not the transmission. Another idea is it's problems with ABS where it's pulsing the brakes unexpectedly.

Any truck people know what could be causing this? I don't know of any good truck shops in the south bay near Sunnyvale. Any shop suggestions in the area would be appreciated since I'm already working on two Mazdas and don't want a 3rd project vehicle.

[Twibs415]

what year is it? is it 4x4? if it is id bet on the transfer case. plenty of issues with those.

[orion4096]

2007 (classic style - before they went to the new style in 07) RWD. Forgot to mention that. Those types of problems are part of the reason I got RWD.

[orion4096]

Center bearing looks destroyed. Good news, I guess. I can wiggle the driveshaft up and down more than 1/4" in the center bearing housing.

[Twibs415]

that's great bad news!

[orion4096]

Pressed the bearing out at 7:30am this morning in the backyard. I had ear protection and still heard a loud pop. Must have been some fireworks.

The bad thing about having a long bed is it needed the $50+ 40mm bearing instead of the $30 35mm bearing. Had to go to a few different auto stores to find one in stock. That pretty much fixed all the stability and shifting problems. Awesome. I should have crawled under the truck a year ago when it first started happening.

[orion4096]

Took the truck for a longer drive and, while most of the clunking has gone away, the rear end started acting a little squirly again. Feels like it's floating or shifting around especially at higher speeds. Makes for a nice turn in feeling but not very confidence inspiring once the rear has to turn, too... Rolled under the truck again and looked over the leaf springs and other parts of the suspension. No cracks in any of the springs. U-bolts still look in good shape and the nuts are tight. Centering bolt still looks like it's there, but hard to tell if it's ok. Bushings look ok, but hard to tell. The only weird thing is that the passenger side overload (bottom) spring looks bent up a little higher than the driver's side. Thinking of throwing some money at the problem and getting a set of bilstein shocks for the rear. Beyond that it looks like pulling off the leaf springs to check bushings/centering bolt or finding out how to test the diff are the other options. Still looking for a local place that can figure it out since I don't want to spend any more time working on the truck ...

[Twibs415]

try to rotate the tires and report back.

[orion4096]

Just did that on Saturday. No change. I had to replace a leaky plugged tire in the front (got a nail 3 years ago). Two new tires went on the rear and old rears went up to the front. Spare got good front tire.

It has 140k miles with the original shocks. It bounces a little more than I would expect. Rear bilsteins are pretty cheap so I'm going to try swapping those out before trying to take out the springs.

[orion4096]

Pulled the rear shocks and they are messed up. Damping varies a lot (from almost none to a good amount) on both compression and rebound. It also changes each sweep. I don't see any obvious signs of oil leaks, but it may have leaked out 10k+ miles ago. Bilsteins for all 4 corners are 350 shipped. It's cool to roll underneath the truck in the street with an impact and pull the rear shocks out in under 2 minutes.