S4_Cinci (I S'edTFA)

If you have a headache, your doctor will suggest aspirin before a CAT scan

April

If you don't have a wheel to swap out, then you've got to try moving them around to different corners. If that doesn't solve anything, have them balanced on a Hunter 9700 balancer with the road force function and somebody who really knows how to use it. Make sure those wheels are still round and on axis. Make sure the tires are balanced. That alone could cause the major vibration you're experiencing.

The other possibility as you point out, is that one of the driveshafts has come unbalanced or perhaps a half shaft is either bent, or joints worn out. You can possibly narrow it down by putting the car on the lift and putting just a bit of power to the driveline to see if anything is visably out of spec. You can also then tug on the shafts to see if there is play.

My first culprit for the engine vibration is probably motor mounts. Next would be flywheel or harmonic damper. Not sure of the mechanics of the old 12v engine and if that is possible though.

You can't intellectualize all repairs and strike with laser precision to solve a problem. Especially with older cars were lots of things may be out of spec. You start with the big obvious ones, and go down from there. I don't know what shops you have in your area, but I would look for one that specializes in these cars or one that does drivelines only. At some point you either bite the bullet and basically restore the car, or you throw it away and buy another.

sudeka

I'm not sure I can tell where it's coming from anymore. I used to think it was the front-right, but now it's so severe when it's happening that the whole car shakes and it's really unclear where it's coming from.

But, you're right, I could try this initially. Since I suspect it's the front right I could switch that side.

sudeka

Is it okay (or preferrable) to swap right-front (suspected problem area) with left-rear. One of the reasons I ask is because of rotational direction of tire. I know you're not supposed to rotate tires that way, but I suppose temporary is fine, unless there's a bad belt, in which case I might find that out pretty quickly!

sudeka

Yes, that's why I think my problem is in the right-front, because of the earlier steering experience. My brother thinks it's a CV joint. I think someone else suggested putting it on the jack and letting it rotate and seeing what can be seen. The only problem with this is the intermittent nature. I went out again this afternoon on the highway and it was perfectly fine. It seems to me right now that I've got to take it in first thing in the morning right after I take it for a little spin on the highway to make sure the problem is happening.

April

opposite direction from which they are intended to turn, is that it can introduce a pull or vibration of their own. I don't know how long they can be run backwards without harm.

When we bought our truck, it had a slight pull to the left. In the deal we asked that the truck be aligned, since that seemed to be what it was. Of course we didn't look closely - which would have revealed that the driver's side front tire was mounted backwards! Since the tire had spent some time turning backwards, once it was mounted correctly, it still had a pull. Something had been tweaked.

So I don't know if you will be able to tell much by installing the other wheel, or how long it takes to tweak the tires (I'm guessing a day/20 miles won't harm it), but it is the cheapest thing you can try.

sudeka

I like the way you put that, meaning we can't necessarily expect to solve the problem on paper without trying a bunch of stuff. Okay. But, I'll bet you'd agree that it's pretty damned inefficient and expensive to take the shot gun approach, even assuming you're starting with the lowest cost/easiest suggestions.

The reason I was so careful at describing this problem in my original message is because I don't think it's a no brainer, and that's why I want people to think outside the box a little bit using all the clues that I gave in my description.

I don't really think it's the tire, because I don't think it fits the problem description very well, but I'm willing to try the tire rotation thing to say for sure. I didn't expect, honestly, given the problem description, that so many people would still be thinking down the tire/wheel path.

April

I can take a guess when something goes wrong, that theory is just as often likely to bite me in the a$$. I've found that the older/more miles, the harder things get to diagnose. The variables get larger. At some point unless you are very attached to the car, it's just easier to start over with a new(er) car.

sudeka

I hear you. I just did that on my VW Golf with a blown head gasket, non-working air-conditioning, broken seat latch, 2 doors, which I donated, took the tax deduction, and bought a 1997 Mazda Millenia S to fix all those problems. I really like the Millenia. I'm not ready to let my Audi go, yet. I think I might be able to figure this out for reasonable cost and get another 50,000 miles out of her. Do you think? (It's got 170,000 right now.)

April

have another 50K left in it. Depends mostly on engine and trans in my book. But there comes a point when it costs too much money in relation to the value of the vehicle, to make it worth dumping more into it. At that point you're better off setting aside the cash you would have spent trying to fix the old car, and using it as a down payment on the next. That point of diminishing returns is different for everyone.

My Alfa Milano Verde has 252,000 miles and the tranny is finally howling up a storm and the LSD is limiting slip any more. I'm very attached to it, so rather than junking it (it's in very good shape otherwise), it's sitting up in the air in the garage, awaiting another transmission. Our 164 has 110,000 miles, and has been very little trouble. Of course just like your German cars, it does require plenty of regular TLC to keep surprises from popping up ;-) I'm giving it another 50K before we replace it with a D2 S8.