Didn't remove the flywheel. I may eventually rotate the TC flex plate 120° once or twice.

Another test drive: the vibration is definitely not felt in the steering wheel. I'll get new tie rods anyway, of course. I'll get the rear tires re-balanced.

 

Curt --

Visiting your thread again.

Last year, as part of a trans mount replacement effort, I jabbed at a couple things on the way to actually replacing the mounts. One of the test steps was to add different "fillers" to the normal gap in the mounts, with the idea of "shoring" (sorry...) them up with different density materials to see if there was any lower-cost lower-effort options. I'd already purchased the new mounts so this was an exercise more than anything else. I tried different things, like sandwiches of 80a urethane, various sections of common and some uncommon hose I had in the bins. I made a shim pack to sit between the diff housing and the saddle in the cross-member, in several different configurations. All were set up to restore the normal height of the gearbox in the car, my ultimate goal. And that's where things got interesting -- by the time I'd stuffed enough test filler into the gap in the mounts or saddle to hold it up in correct position, the amount of gearbox noise and such passed to the tub was more than excessive. The easy solution of course was to just install the new mounts, at which time the noises and transmitted vibrations ceased and all was well in the cabin again. Plus no hot air coming up through the console, my initial target symptom.

Another data point may be a Bill Ball report on replacing gearbox mounts, when he found a similar vibration after just that effort alone. I don't remember the final solution, but his work and reporting was extensive. A little searching may get you some more on how he was working the symptoms.

back to work....

 

Hi Bob,

I had quite the opposite experience a couple of years or so ago. I was experiencing some "contact" causing a "buzz" through the body. Stan suggested making a packer so I got an old inner tube and cut a couple of strips about 1 inch wide and about 6 inches long. I formed the strips into a roll such that when compressed the packer filled the gap. I wrapped the packer with a couple of passes of Gorilla tape.

Transmission vibration issue was resolved and still working fine to date in so far as I can tell. I figured the nature of the inner tube material would allow it to fit the profile nice and evenly.

Strips of inner tube


Packer mounted


Rgds

Fred

 

Good news!

This will hopefully lead to a resolution for Curt.

 

Well, I had an interesting sight here at Camp 928 - Dave C and Jay Kempf driving off together in my car.

The verdict: front right wheel bearing. Dave had forgotten about the loose tie-rod, but it could be both. I tried to "Tom Sawyer" them into installing a new tie rod I had on hand, but ended up having to do it myself a few days ago. Result: the 2100 RPM/left turn vibration is 80% reduced.

Since then, I had the rear left tire re-balanced, the one that the weights had fallen off. No change.

I don't have the feel for checking bearings, unless they're way off. The right might be a bit looser than the left - there's a slight knocking noise when I yank on 'em top and bottom. I suppose that at 106,000 miles, new bearings would not be wasted effort. I got some good instructions on how to deal with a worn spindle.

By the way, the tie rods I got from Roger are different. They screw in fine, of course, and can be made the same length. Dr Bob asked me to mention this - he fears that replacing only one end of a tie rod might not always work. From the photo, it appears that you'd be OK, barely.

 

I think the tie rod you have is for the early car
The thing with front wheel bearings is that the inner race of the inner wheel bearing can deform on the bottom of the spindle,
thus adding clearance /wear to the slip fit of the bearing.
This then will give the feel of loose wheel bearings, in the 12 to 6 arc. even though they may be properly adjusted.


So dont try to adjust this play out of the assembly, as this will lead to increased wear of the bearings and possibly total failure.

Adjust the bearing per the book, make sure the sliding surfaces are all dressed before they are installed.
IE sand down the flat washer so its smooth on both sides, and the face of the nut.

 

Thanks for that, Stan.

I surely have homework to do. Dave and Jay were concerned with spindle wear, and suggested a crude but effective technique to fix it.

 

NOTE the spindle of the 928 all years is made of the softest metal,
thus it deforms over time due to the hammering nature of the wheel bearing race.

Beyond inspection the best thing to do is replace the part with a new one,
as a used part will probably be deformed as well

 

 

Luckily there was no call to allow Jay to drive

Your method is too subtle. I require three repeat transmissions or 2x4s to get things through (just ask Jane...)

Is it the exact same vibration, provoked in the same way, just, now, reduced in amplitude? Or has it 'moved' or is there a non-trivial change in the procedure necessary to make it noticeable?

Recall that I was able to feel the vibration more-or-less instantly on Schoolhouse Rd. Front-right locus was evident to me by the time we turned onto 8/9. Subsequent driving was to rule out other potentials and to gather additional confirmatory data.

Does the vibration still become more-noticeable when (some) weight is shifted to the front-right?


The front-right is definitely too loose. But, with the tie-rod accounting for 80% of the vibration I'm no longer willing to bet an important body part on the FWB. You've got two other ball joints on that side.

Given that one inner tie-rod joint was dead, Occam suggests that the other could be ill too. We did check that one, however, with the suspension unloaded on your two-post it is very difficult to detect anything other than very-serious slop.

I would suggest putting your S4 on your 4-post - so that the suspension is loaded and thus transmits more force through the suspension - and going through the suspension check procedure in my inspection guide so as to check all the suspension joints.

 

Dave - the ones I just installed on my car this Spring were NOS (never used). I tried 2 used sets, all had wear equivalent to the ones originally on my car, and such wear was easily seen visually, and by test fitting new bearings. I found the crude fix to not be effective in my case after some mileage (maybe not crude enough?). That wheel still would not adjust to the point where it didn't have significant and audible play. Once the new spindles where on, the bearings adjusted properly. It was truly like night and day.

Curt - if you have not yet checked bearing adjustment, do that first (follow the WSM - just snug enough to be able to move the thrust washer with a screwdriver tip). If, after remounting your wheel, you can still feel significant movement (you will always feel a little movement when the assembly is cool) when tugging at 12 and 6 o'clock, and you can still hear that "clunk" when tugging on the wheel (which I heard on your car when tugging on the wheel last Sunday), then it would be time to pull the hub and inspect the spindle for wear. It may be fine, and you just need new bearings. Report back when you get into it.

 

Will the 87-88 spindle work on 89+? Is it because it was reworked for the tire pressure system?

 

Dave - nothing changed except the amplitude. That includes an increase under acceleration when turning left. Deceleration, too, I think.

Note, however, that it was my observation that the vibration was engine speed related, which seems quite wrong at this point.

I will comply with the suggestions! Thanks.

 

Fifty years of working on cars and listening to customer's "self diagnostics" of their problems, I though I'd heard it all.....but my mind is finally blown.

Vibration from engine rpms and vibration from a loose piece in the steering are so far removed from each other, my head simply refuses to comprehend your words.