First, some background...all shocks, inner/outer tie rods have been replaced in the last year, by a shop that knows what they're doing. It was recent, but not so recent that you'd expect it to cause what's happening now.

I was accelerating up a slightly bumpy on-ramp/flyover to get on the highway, when suddenly there was a violent vibration in the front end. I immediately slowed down until it went away, then everything seemed fine. This happened once again, although I wasn't accelerating particularly hard, however it was a similar environment. Also, now that I'm completely paranoid and being rather ginger with it, it seems that the steering is less precise? I have to turn the wheel more to turn, although it's quite smooth, nothing FEELS wrong, really. It's entirely possible this last bit is my imagination.

I know my steering rack probably will need to be rebuilt at some point in the near future, and the rack bushings aren't great, but after replacing the tie rods it really did seem quite solid and fantastic, at least relatively speaking.

Any thoughts on what this might be?

 

That was happening to our 1989 928S4 and it turned out to be tie rod ends.

When they were replaced it was an immediate difference in steering feel, much tighter, and no more shimmy after hitting a bump at speed.

The way you described your symptoms it sounds like the perfect scenario for bad tie rods, light front end and bumpy as you were going up a hill at speed.

I read your preface that these were recently done, but they can quickly check them with the front raised and grabbing the 3 and 9 o'clock position of the tires with your hands and push/ pull side to side. There was a noticeable clunk when this was done with our 928. In fact very surprising how loose they were and how smooth it was driving most of the time. Probably just got use to the vague steering as the tie rods gradually went away over time.

HTH

 

Also check the A arm bearing caps. Mine had come loose (like finger tight on a couple of the bolts) and the front would violently change direction when the front end load changed. It wasn't doing this because the front was toed out so far that it stayed toed out under load, but once I had the alignment fixed I almost wrecked the car as the shop missed the loose suspension parts (I don't go there anymore). Once the static alignment was right, it would change from toe in to toe out mid corner.

 

Before you lift the front lay on the ground and look behind the wheel have a helper turn the steering wheel back and forth
look at the tie rods at the wheel and the rack look at the rack mounts
see if anything else is moving
worn rack bushings will let the rack move
what size wheels and tires do you have

 

Thanks guys. I'm going to be annoyed if it's tie rods again so soon but that would seem to fit the symptoms.

My wheels are 17" Cup 2s...tires are 225/45 I think.

I'll do the tests suggested above. I'm not sure exactly what A arm bearing caps are though...

 

Go get your wheel balanced checked, usually the first thing to do.

 

They probably have a different name, but they're the little assembly that holds the A-arm in place. 2 or 3 bolts go in from the bottom.

 

Ahh, OK. I will take a look there.

Regarding the other tests...wheels on the ground, someone moving the steering wheel: Tie rods seem OK. Quite a bit of rack movement. Is it more than before? I think it probably is. I can definitely see this causing the more sloppy steering feel. Not so sure about the only-twice-so-far vibration.

Wheels off the ground, try to move in horizontal and vertical axis: Not much movement. Passenger side horizontal access a little, but not enough to actually hear any "clanking" (tie rods were so bad on my 924 you could hear them).

The only obvious thing I see is the rack mount bushings. (*sigh*) I've been putting this and motor mounts off so long...not going to be able to keep doing that.

Wheel balance: Never thought of that...it was done not long ago, my tires are still good...but I could have thrown a weight or something. Good idea...

 

when you get the wheels balanced have the rack bushings replaced.,
out of balance wheels can shake the ship out of a rack with worn bushings

 

My understanding is that rack bushing job is pretty big and most of the way towards doing motor mounts, which I also need to do. The problem is I have to do it in my driveway on a bit of an incline, and I'm not too excited about putting it on four jack stands on an incline. And I don't think two will work well when you lift the motor.

I may need to take it to the folks who did my suspension, but that's going to be some bucks I didn't want to spend right now....

FWIW, I've noticed the steering wheel is not as centered as it used to be either, I don't think. Not sure if that is important...

 

Hi Jeff,

No, not really. It is a R&R of a steering rack, which is an endeavor, but not as big as a MM change.

Unless someone has a short cut of replacing the bushings while the steering rack is still attached to the car, the easiest would be to remove it and press out the old bushings and press in the new ones.

Your shop could do it and while there can also make sure all the rest of the front steering stuff is good as well check the balance of the wheels.

HTH.

 

When the rack bushes go all it takes is a bump at a specific frequency and off the assembly goes just the same as if the rod ends have gone. I believe folks have attempted this repair with the rack still in the car but to my way of thinking dropping the rack and getting the remains of the bushes pressed out is clearly the way to go.

You might also consider going the Delrin route as many of us have already but the stock bushes are perfectly OK [until they go mushy]..

 

Hi Fred,

Very interesting failed steering rack bushing symptoms and is why I recalled my tie rod end failure symptoms. Thankfully I never had such a steering rack problem.

The bushings must be pretty shot to act that way.

 

It can be done while the rack is mounted on the car, or rather, loosened. I replaced rubber/metal bushes on a previous rack with delrin bushes without taking the rack completely off. The caveat: the old bushes weren't that old, I had replaced them a few years previously. Technique was simple, socket and c-clamp.

 

Thanks....it sounds like something that just needs to get done, and not necessarily at the same time as the motor mounts.