4 wheel alignments and the steering box

sgiangregorio · February 12, 2006

First I'll give you the question, then the background.

Q: When performing a 4 wheel alignment on a 2002 Tahoe (or similar) does the tech disconnect or do anything at the steering box itself, or are all adjustments made elsewhere?

Here's the background and why I ask...

I had 4 new tires installed today, and have the customary 4 wheel alignment done as well. When they returned my vehicle to me they said "your steering wheel has a lot of play in it, so we got the wheel as straight as we could. Your steering box has some play."

I thought "it's always been that way" as I recalled always having a little. Then I drove my truck and I felt like I was all over the road. Really subtle changes to the steering gradually sent the truck off course, but I defintely had to move it more than I remember to make a clear direction change.

Now, of course, memory can be tricky. Perhaps my mind is playing games on me and I'm really just getting used to the new tires and the stronger "grab" and better traction, and the steering is as it always was.

The reason I ask is I don't want to accuse the shop of possible causing or exaggerating the problem if they didn't even touch the steering box at all, or anything that would be related to it to cause this - again, if it's even worse than it was. It could be the new tires. Anyway, they said it would be like $750 to replace it. Yikes.

Thanks all.

Larry · February 12, 2006

No, I doubt they did anything with the gearbox….unless, they messed with the worm gear preload, which is unlikely. Most shops are smart enough not to mess with the worm gear preload. The term 4 wheel alignment is used loosely in the industry. A vehicle with non-adjustable rear suspensions like a solid rear axle Tahoe or truck should only need a thrustline alignment but most shops push 4 wheel alignment for more money…plus it just sounds good.

Most likely the change in the toe setting affected the steering wheel index and a change in caster (as well as toe) will affect the road feel. Sounds like the toe maybe set excessively out or the caster set too low if the steering feels “touchy”. Then again, maybe this shop actually has your front end set up correctly and you are just not used to it actually being set up correctly. If by chance you have aftermarket wheels especially, tall wide bling bling wheel the vehicle will may not be receptive to the specs they used to set up your front end. Sometimes, after big tall and wide bling bling aftermarket wheels the caster has to be set up as much as a degree higher than original to maintain road manors.

asepgrad98 · February 12, 2006

they said "your steering wheel has a lot of play in it, so we got the wheel as straight as we could. Your steering box has some play."

what he means is before you set the front toe you set the steering wheel straight. If there is a lot of play then it makes it more difficult to have the steering wheel straight after you start driving due to the play in the gear box.

sgiangregorio · February 12, 2006

they said "your steering wheel has a lot of play in it, so we got the wheel as straight as we could. Your steering box has some play."

what he means is before you set the front toe you set the steering wheel straight. If there is a lot of play then it makes it more difficult to have the steering wheel straight after you start driving due to the play in the gear box.

<{POST_SNAPBACK}>

Right, this is exactly what he explained it as. He said they did the best they could, and they did, it's pretty darn close.

My rims are stock, even the tire size is stock (265/70/17). They showed the printout and everything is now in alignment. Some items were out, but not way out. And to be fair, they did say a thrustline alignment, not a 4 wheel alignment. My fault there.

So it could very well be that a combo of the new tires, and the alignment are just making it feel this way. And Iwouldn't say it's touchy, as much as it's less touchy, say between 11 and 1 positions. The vehicle will steer in the direction (within those positions), but it's just moer subtle than I remember. Again though, could be my imagination.

I just don't know how much play is normal. And it could have always been there. Crazy huh, you drive it everyday, and you can't recall how it was "before" if there even was a before.

But it does sound like a typical front end alignment with a thrustline alignment would not typically have a reason to mess with the steering/gear box. I'll probably ask them if they touched it at all, but the info you guys are providing is helpful.

But is there any time that a shop would do this, and would they typically make the consumer aware of it if it's out of the ordinary?

Thanks.

AirForceAngler · February 12, 2006

Have all of the front end parts looked at. It may be something as simple as a bad pitman arm and/or idler arm. I had an idler arm go bad several years ago that loosened up the steering a bit. These are hard to grease so if you take it somewhere to get your oil changed, they may not get the grease gun on them all the time.

I'm not certain, but the rear alignment on Tahoes may be adjustable, since they are a 4 link style versus leaf springs.

sgiangregorio · February 12, 2006

Thanks. The truck is out of warranty, so I'm trying to be cautious about not chasing a red herring. Like I said, it could very well have been this way before, and I'm just noticing it now cause they said something about it. You know how the mind works. I was just curious, more than anything, if the alignment involves loosening anything on the steering box. Sounds like no, typically.

sgiangregorio · February 13, 2006

No, I doubt they did anything with the gearbox….unless, they messed with the worm gear preload, which is unlikely. Most shops are smart enough not to mess with the worm gear preload.

<{POST_SNAPBACK}>

Actually, Larry, can you explain what the worm gear preload is?

And to your points about caster settings and all, since the tires are stock size on stock rims, I would think as long as they are within Chevy specs, they would be ok and wouldn't need any additional tweaks, right?

Thanks.

Larry · February 13, 2006

The worm gear preload basically is the amount of pressure of the ball on the reciprocating gear in the gearbox that determines steering sensitivity and returnablity. There are other factors that can relate to sensitivity and returnablity as well such as caster. A non-rack and pinion steering gear box is typically called the reciprocating ball type gearbox.

Regarding the alignment specs being set at GM specs. Well, as with anything mechanical thing there are variances in manufacturing. It could be that a stack up of tolerances on your truck may require higher than normal caster or toe. When I was at the GM Tech hotline it was not uncommon to have to advise techs to add a degree or more above spec in caster to correct brake pulls and sensitive steering issues. That was usually the case with aftermarket wheels and tires. DCX is currently loading up the 300C, Magnum and Charger with tons of caster above spec to correct steering pulls right now to avoid arbitrations.

Here are instructions to adjust the worm gear preload. These are for off-vehicle but the preload can be done in vehicle as well, albeit not easy. It is typically NOT a good idea to mess with this setting unless you really really know what you are doing. Sorry the pics did not copy.

Chances are they did not mess with it and it is not causing your issue anyway….but plausible.

(***I forgot to add that you could actually have more noticeable issue with the EVO steering now that the alignment might be set up correctly. Have somebody hook up a scanner and look for any C04** DTC codes. As you can see, there is not clearly one single possibility for steering sensitivity. )

Worm Thrust Bearing Preload Adjustment - Off Vehicle

Thrust Bearing Preload Adjustment

Notice: Refer to Fastener Notice in Cautions and Notices.

1. Turn the adjuster nut assembly clockwise using J 42882 until the adjuster nut assembly and the thrust bearing support are firmly bottomed in the steering gear housing.

Tighten

Adjust the adjuster nut assembly to 29.5 N·m (22 lb ft).

2. Place an index mark (1) on the steering gear housing even with one of the holes (2) in the adjuster nut assembly.

3. Measure back counterclockwise 13 MM (.5 inch).

4. Place a second mark on the steering gear housing.

5. Using J 42882 and a torque wrench, turn adjuster nut assembly counterclockwise 22-32 degrees to align the hole in the adjuster nut assembly with the second mark on the steering gear housing.

6. Install the lock nut.

7. Hold the adjuster nut assembly in position to maintain alignment of the marks.

8. Tighten the lock nut using J 42882 , J 43435 and a torque wrench.

Tighten

Tighten the lock nut to 109 N·m (80 lb ft).

9. Adjust the pitman shaft over center preload. Refer to Pitman Shaft Over-Center Preload Adjustment - Off Vehicle .

sgiangregorio · February 13, 2006

Wow, thanks! Awesome data.

I called the tire place. They confirmed that they never touch steering boxes, as usually, you just make it worse. They believe that what I'm experiencing is a combination of:

1) New tires

2) Me thinking about it

3) A new tire tread depth of a full 17/32" which can create the feeling of "squirminess" until it breaks in

I'll buy that. I'll monitor it and see if I get used to it, rather than having it feel like I'm always adjusting, which I don't think I am.

Thanks for all the help. As always, awesome info here.

sgiangregorio · February 16, 2006

Just an update to close the loop on this. It was a faulty EVO sensor. Just coincidence that it happened/was noticed after the alignment. Perhaps the new tires made it more pronounced.

But tonight, I greased the intermediate steering shaft, and while I had it out, I pulled out the EVO sensor and sprayed it down with WD40 and spun it like crazy (hoping to clean the internal contacts). I put it back in and my truck was back. No more steering clunk and the power steering felt normal again. I think it was over-assisting before, so I felt all over the place. I felt much more in control again.

Thanks for all the help guys. This place is really great.

Larry · February 16, 2006

Glad it worked out for you. EVO steering, like Autocrap, is not one of GM’s shinning stars but is a profit center for service parts. At least GM was smart enough to discontinue EVO.