Testing for Bad Steering Gear
 

After replacing just about everything in the front end of my 190e I'm having a fairly difficult time tracking down a wander at highway speed. One thing I've noticed is that my steering wheel doesn't really seem to return to center very well if at all. I've heard this can be caused by overtightening the steering box and when I went to try and loosen it I found the locknut seized. If I turn the wheel 180 degrees while stopped and start driving it'll correct to about 50-60 degrees of center. I have just about 1 inch of play in the wheel but it is fairly heavy to turn as well.

Is there anyway to determine the gear is bad before I drop $300 on a new one?

I believe my wander is due to the steering wheel not wanting to center and following any imperfections in the road. Alignment was done and caster is 10.2 both sides. I've replaced the following: LCAs w/ ball joints, entire tie rods, center link, idler arm bushings, steering damper, springs and struts are also new. Am I missing anything else?

Interested to see what everyones input is, I am preparing to do the same overhaul of my 190e. My car has excessive play in the steering, but I've always attributed that to very worn tie rods, center link, idler arm and damper on top of the pump being very audible at low speeds.

I thought the same and I'm leaning towards thinking worn parts was actually hiding some of the issues. My car didn't wander before and I'm thinking the play in all the joints hid the wandering. Now with all new components its nice and stiff and no longer hiding it. As I think anyone would suggest I'd do all the other things before the gear itself.

1" of play or less is normal for steering systems using pitman-arm drag links. The heaviness and reluctance to self-center suggest that someone has adjusted the box to an excessive degree. Spray a good penetrating oil on the locknut and give it some time to work its magic. There's a balance between enough resistance in the box and being too loose or too tight. The box adjustment will NOT remove slop in the steering wheel.

If I loosen the box after it being overtightened will it be okay, I've heard overtightening will ruin it and its been that way for least a few years. I'm happy to throw a rebuilt unit in but anything else I should check before doing so?

My 300SDL was grossly overtightened when I got it, took two hands to park! I backed it off and it was fine. You don't really have anything to lose by trying. If the box is junk, it's junk. If you back it off and everything is fine, that's $300 and several hours of your life you didn't have to spend on it. Just don't go down the rabbit hole of trying to eliminate slop in the wheel, if you have 1" of play, leave well enough alone - the rebuilt/new box will too.

Got it, I'll try again with more rust penetrant, unfortunately the nut is directly under one of the intake manifold plumes and I can only get a wrench on it, no breaker bar.

I did notice that the freeplay is in the coupler. I could move it back and forth by hand while under the car with absolutely nothing happening internal to the box. Is that the normal freeplay?

Yes. The steering shaft acts on the worm gear. The pitman arm is attached to the sector gear. The adjustment nut acts on the sector gear. No matter how tight it gets, it will have no effect on the slop present on the input shaft/worm gear.

The adjustment to the steering box is to help preload the sector gear to prevent excessive wandering and weaving due to the box being too loose and input slop from the steering wheel. When the box is adjusted too tight, you wind up with a different kind of wander/weave due to the box just staying wherever you turned it instead of self-centering and following the road contour. As I said, there's a fine line between too loose and too tight. Too loose is definitely better and safer than too tight.

Awesome info, just noticed you're in hill country, I'm in Pflugerville, small world!

Just be happy you are not driving a 6.9, not possible to adjust the box in situ, you have to remove it and do it on the bench.

As usual Diseasel has given us a lot of detail to consider. I have two things to mention about it.

I disagree that 1" is the best you can do on free play at the steering wheel. You can pretty much get it to zero without binding if you are careful on the adjustment in my experience. I have done this successfully with boxes with over 300K on them.

Also I believe the OP mentioned finding play in the coupler...to me that means play between the steering shaft and the connection at the steering gear, which would indicate a worn or possibly loose coupler.

I don't believe the play is in the coupler, just at the coupling. I can move the coupling and shaft without anything happening within the box.

Grabbing a 19mm crowfoot this afternoon and trying the lock nut again.

Can anyone think of any causes for non-centering that wouldn't involve the steering box? I know lower ball joints are usually to blame but those were replaced with my LCAs. I don't mind spending the money on a rebuilt gear box, if that would solve the issue.

I'll be impressed if you can loosen it with a crow foot. l believe my Indie did it from below with a box end and heat.

as for the play, if it is not loose between the shaft and coupler and it is as you say at the coupler then it must be play in the connection of the coupler to the steering box.

I'm going to try, if I can't I'll probably grab a coswroth box and have that rebuilt.

Just to chime in, came across this in the online manual, apparently the maximum amount of play should be no more than approximately 25mm (.98 inches). Not sure if that is a unrealistic range but thought I would post the link. https://www.startekinfo.com/StarTek/outside/11832/Resources/201Create/PDF/10011.pdf