GMT800 steering weirdness

So there's lots of threads out there on various forums about the steering on a GMT800, but googling through them I haven't yet managed to find any that address the specific issues I'm seeing.

The truck in question is a 2007 Silverado 2500HD classic, crew cab, shortbed, 4x4, with the LBZ duramax.  140K on it.  I've been trying to chase down a weird steering issue for a while, without much luck.  I notice it mainly at freeway speed, basically the issue is that going through a constant radius sweeper the truck won't hold a given arc.  You turn to the point you want, the truck turns a bit more, so you correct, it's OK for half a second and then you have to correct again to stop it going off the other side of the lane.  Repeat that for as long as you're driving.  I notice it mainly when towing my 24 foot triple axle enclosed trailer, although the same tendency is also present without the truck loaded.  I'm not sure if it's less noticable then, or if it's just that I get more annoyed at it when I'm tired halfway through a 3 hour tow home from a track day.

Tire pressures are fine, the truck has been aligned, and I've replaced a host of steering components (steering box three times, idler and pitman arms, intermediate shaft).  The dealer mechanic who did the initial steering work looked at the ball joints and tie rod ends and pronounced them OK, although I haven't personally inspected them. 

I had a 2002 Silverado before this (same 2500HD CC/SB duramax), and it didn't do that.  It was a 2WD through, and I'm not sure if the front suspension geometry is the same or not.  One other difference was that the '02 had airbags and the '07 didn't.  Thinking that maybe I had too much tongue weight, I added airbags to the '07 to see if it helped but no dice.

Any ideas?

I have a ‘08 GMT 900 2500HD 4x4 Crew Cab Long Bed with a LMM. I haul travel trailers for a living. 

I experienced something similar but not exactly like what you experienced and it was a loose wheel bearing hub on the right side that when going through a sweeping turn, mostly left handers, you start going through the curve and the wheel bearing would pop back into place and the front end would get all squirrelly. It did it for a while before the wheel bearing decided to start making noise. 

I also know that the U Joints in the steering shaft can go bad and cause the truck to wander. 

Whatever it is, it’s definitely an issue with the suspension or steering. 

SyntheticBlinkerFluid said:

I have a ‘08 GMT 900 2500HD 4x4 Crew Cab Long Bed with a LMM. I haul travel trailers for a living. 

I experienced something similar but not exactly like what you experienced and it was a loose wheel bearing hub on the right side that when going through a sweeping turn, mostly left handers, you start going through the curve and the wheel bearing would pop back into place and the front end would get all squirrelly. It did it for a while before the wheel bearing decided to start making noise. 

I also know that the U Joints in the steering shaft can go bad and cause the truck to wander. 

Whatever it is, it’s definitely an issue with the suspension or steering. 

I bought the truck a couple years ago and the seller had both front wheel bearings replaced right before the sale.  When you say loose do you mean worn out, or installed improperly?

U-joints in the column itself, or the intermediate shaft?  I've replaced the intermediate shaft, so unless those U-joints were bad from the factory it should be good.

In reply to codrus :

It really could be either, especially if you hadn’t done the replacement. Mine was worn out. I replace mine once a year only because I put 80k+ on my truck a year. 

If you replaced the intermediate shaft that should be ok. 

Also, I’m pretty sure the HD trucks are fairly similar mechanically between the two generations, so these trucks have inner and outer ball joints, that could be something to check out if you already haven’t. 

SyntheticBlinkerFluid said:

In reply to codrus :

It really could be either, especially if you hadn’t done the replacement. Mine was worn out. I replace mine once a year only because I put 80k+ on my truck a year. 

If you replaced the intermediate shaft that should be ok. 

Also, I’m pretty sure the HD trucks are fairly similar mechanically between the two generations, so these trucks have inner and outer ball joints, that could be something to check out if you already haven’t. 

I'll check the bearings.  I drive it way less than you (it's done maybe 5K since I bought it), but it's worth looking at.  Will look at the ball joints too, thanks.

Defective EVO steering sensor ?

I haven’t seen anything about the shocks being replaced. Bad shock could be causing an abnormal amount of wheel travel leading to a near bumpsteer condition. If you have replaced them, I hope there weren’t the cheapest things available.

FYI, shocks should be really be on their second replacement at 140k....

In reply to codrus :

I said ball joints, I meant to say Tie Rod Ends, these trucks have inner and outer tie rods. 

Are these still open wheel bearings, meaning can be taken apart to be greased? If so, then they might not have tightened the wheel bearings enough or might have over-tightened them. It's difficult to gauge just how tight they're supposed to be, and some people default to too far in one direction or the other. Jack each wheel up and give it a shake. If the wheel moves much maybe the bearings just need retorqued.

I installed new Bilstein 4600s when I bought the truck (the shocks it came with were blown), so those are fine.  I don't think the wheel bearings are designed to be greased -- it's an bolt-on hub/bearing assembly.

On the 2500/3500, the front suspension is the same 2wd or 4wd, both a-arm setups with torsion bars. It may be worth changing the tie rods at least, they tend to wear out about the same as the wheel bearings. Which reminds me, I need to change them on the Suburban.

Check the bearings first.  It's a known issue in those trucks, although if it's loose enough to cause that issue you would have likely heard it for 20k miles.

Sometimes the check ball in the PS valve gets gunked up too and it offers on/off pressure to the box.

Did you ever solve this issue? I'm having the exact same issue on my GMT800

cletuz said:

Did you ever solve this issue? I'm having the exact same issue on my GMT800

I did solve it, yes.  There's a metal tube under the dash that the steering shaft runs inside, with a plastic "bearing" at the bottom that centers it.  AFAICT GM doesn't make a replacement for it, but this Dorman (ugh) part solved the problem for me.  It is a giant PITA to install, though.

https://www.summitracing.com/parts/rnb-905-512/make/chevrolet/model/silverado-2500-hd-classic/year/2007

codrus (Forum Supporter) said:

cletuz said:

Did you ever solve this issue? I'm having the exact same issue on my GMT800

I did solve it, yes.  There's a metal tube under the dash that the steering shaft runs inside, with a plastic "bearing" at the bottom that centers it.  AFAICT GM doesn't make a replacement for it, but this Dorman (ugh) part solved the problem for me.  It is a giant PITA to install, though.

https://www.summitracing.com/parts/rnb-905-512/make/chevrolet/model/silverado-2500-hd-classic/year/2007

 

Crap. I already replaced that bearing, still have the issue. 

I have the same truck, and have replaced tie rods, ball joints, pitman and idler arms, wheel bearings, and steering gear at different times. 

The ball joints fixed the drifting-while-steering sensation for me, so I would take a close look at those.

(That being said, everything in the chain can wear out so it doesn't hurt to inspect everything while you're in there)

average_bear said:

I have the same truck, and have replaced tie rods, ball joints, pitman and idler arms, wheel bearings, and steering gear at different times. 

The ball joints fixed the drifting-while-steering sensation for me, so I would take a close look at those.

(That being said, everything in the chain can wear out so it doesn't hurt to inspect everything while you're in there)

 

I should mention I replaced inner/outer tie rods, pitman and idler arms and idler arm bracket, as well as the steering column bearing. I only noticed this issue after replacing these parts. 

Update: my passenger side ball joints were worn. I replaced all 4 ball joints and the wandering is gone. Funny how different parts can cause such a similar issue.

I'm curious... is there any benefit to using poly bushings in the lower or upper control arm on these?

Im generally not a fan of poly bushings for street driven vehicles but am curious