The Project Pad

Today I present you with today's headache with this $@#$@!! car: driveshaft misalignment!

Here's a view from the front:

The photo doesn't show it very well, but it seems the driveshaft is aligned well from the rear diff to the center support bearing. But from there forward to the transmission, it's decidedly crooked! No really, I caught it trying to lift a $20 bill out of my wallet this afternoon. :tard:

Here's a view looking forward from the rear:

You can clearly see the two sections of the driveshaft aren't aligned with each other, and the transmission seems to be sitting a bit toward the right, although it doesn't seem off by *that* much. The engine/trans are sitting on all 4 mounts and I really didn't have any trouble lining them up.

WTF? :? Anyone got a clue what's up here?

By the way you'll notice the center bearing is pretty well as far as it can go to one (the left/driver's) side. Initially I thought that was the problem, but as I said the alignment from it to the rear diff seems pretty good, and my two other driveshafts, one of which came out of this car, are both offset to the same side so presumably the bearing's not on backwards.

Re engine/transmission brackets, I'm using all the same ones I used on the 4KQ - is that wrong?

What center bearing is on there? It is missing half of the mounting tab and that is what is causing the misalignment. You should be able to center it in the tunnel. I would weld on a piece of metal so it looks like the other side.

Not suppose to be.

Nope, there's nothing missing from the bearing!

I've got 3 driveshafts here: the one in the car is from an urquattro, and one from a 4KQ, both have had their center bearings replaced with BMW ones. The third is the original from the car, with what looks like the original bearing. All the bearing mounts are asymmetrical, with the passenger's-side "leg" being longer than the driver's-side one.

They are not suppose to be lined up. U joints have a tendency to "snap" out of strait if they are lined up, so they offset them slightly to keep a constant angle on the U joint.

Are you sure about that? The Bentley shows the procedure for setting the driveshaft alignment using a factory tool. In the illustrations, that tool looks like it's just a straight metal bar.

That would be news to me. Any hotrod or motorsport application I have ever seen where they are fabbing in new tunnels and have hte freedom of making the bearing wherever they desire, they always kilter them to make them not run on the same concentric plane.

The Bentley procedure for my 90 has you offset the drive shaft in the vertical plane. The tool you mention accounts for this. I just looked at my bearings and they are definitely not that asymmetric. It will probably work the way you have it but like Hank mentioned the only thing you don't want to do is run it perfectly strait.

Yeah, maybe what I'll do next is take some measurements on this bearing vs. the stock one. I certainly don't remember the bearing being so close on the driver's side in my 4KQ. The bearings on the two 016-compatible driveshafts I have came from different sources, but they appear to be identical.

It also seems like the rear of the transmission is farther to the right than it should be, which I find odd since the mounts seem to line up perfectly. But of course the transmission and mounts weren't made to go into a B3! I don't suppose anyone out there has a photo of a stock B3 showing how the output flange lines up? I did a bunch of looking on the "projects" forum but couldn't find anything.

Hmmmm.... Maybe it is different for the 80/90 compared to the 4000. I don't recall the bearig being offset on any of my driveshafts.

Okay, so, the weirdness continues. Take a look at this:

You can see the snub mount is waaay off toward the passenger's side. The rubber part isn't in there, but I suspect if I tried it wouldn't even fit without hitting. Now here's the "rest of the story": this engine, and its predecessor, had the same problem in my 4KQ! On that car, I actually modded the snub bracket on the car in order to make it clear. In the case of that car I figured it might be a bent frame, but two cars in a row with exactly the same problem? I ain't buying that.

So now I'm thinking the engine mounting brackets might be wrong. I got a partnumber 855 199 307A off the left one but that number doesn't seem to correspond to anything so maybe it's just a casting number?

In any case I could use some help here! Take a look at this:

If anyone with a properly-fitting 5-cylinder in a B3 chassis (or even a B2) could make a similar measurement, from the side of the block straight over to the front mounting bolt on the frame for the left-side engine mount, I'd really appreciate it! As you can see in the photo, on my car it's maybe 5-15/16" - if yours measures significantly less I've probably got the wrong brackets.

Gahhh, I just re read all the b5 a4 shifter swap stuff. I'm never gonna make the deadline. here is to trying though.

Yeah tell me about it! You read some comments here (and elsewhere) and people make these things sound as easy as swapping a light bulb. It's more like taking a blender and adapting it to fit in the socket and light up.

Is your rear subframe square?

Both of my 90Q'S and I thought 4KQ's had oval holes in the mounts so the engine could be centered....

I tried to measure my 90Q to compare with your pic but with the radiator/shroud in place I can't get to the mount bolt from the top.

I know rye support bearing on my b3 is not asymmetrical. I do not know if that is a 4k thing, but you may want to swap out the bearing for a b3 one.

ur20v wrote:Is your rear subframe square?

As far as I can tell...? It doesn't look like it's ever been removed so presumably it's installed straight, and it doesn't look damaged.

mrmotorhead13 wrote:Both of my 90Q'S and I thought 4KQ's had oval holes in the mounts so the engine could be centered....

I can't remember which are which, but of the four engine + transmission brackets, I seem to remember two have oval holes, one has a very large hole (so it can adjust both fore-aft and side-to-side) and one has a hole just large enough to accommodate the bolt. The end result is the engine + transmission can adjust a little fore-aft and very little (less than 1/4") side-to-side. To get the front snubber lined up, I'd say it needs to move around an inch.

mrmotorhead13 wrote:I tried to measure my 90Q to compare with your pic but with the radiator/shroud in place I can't get to the mount bolt from the top.

Hey thanks for trying! :-) I tend to forget that with the radiator etc. in there, there isn't much access to the stuff lower down.

rs4tech wrote:I know rye support bearing on my b3 is not asymmetrical. I do not know if that is a 4k thing, but you may want to swap out the bearing for a b3 one.

That's really weird, because the one on my original driveshaft is! And everything I find online says the B2 and B3 bearings are the same, including the one 034 sells: http://www.034motorsport.com/chassis-co ... p-351.html.

If I get some time tonight I'll try to take some measurements and photos of the various bearings I have. I'm 99% sure the 80 one is offset, but it may be offset less than the ones that are on the 4KQ driveshafts (which are actually BMW parts).

elaw wrote:

rs4tech wrote:I know rye support bearing on my b3 is not asymmetrical. I do not know if that is a 4k thing, but you may want to swap out the bearing for a b3 one.

That's really weird, because the one on my original driveshaft is! And everything I find online says the B2 and B3 bearings are the same, including the one 034 sells: http://www.034motorsport.com/chassis-co ... p-351.html.

If I get some time tonight I'll try to take some measurements and photos of the various bearings I have. I'm 99% sure the 80 one is offset, but it may be offset less than the ones that are on the 4KQ driveshafts (which are actually BMW parts).

Looking at the pic of the one on 034's site, that one is symetrical, and pretty much the way I remember the bearings being on all of my audis so far. I wonder if it got changed somewhere along the way with a bmw part or something similar. I would say either weld another tab on the short side and slot to adjust or get a new bearing and be done with it.

Yeah, right now I'm leaning toward the "weld on some tabs" solution. With my mad welding skillz combined with a MIG machine that cost almost $100.00, it should hold together for at least a week!

Is the center support bearing oriented with the dished side to the rear? I couldn't tell from the photo.

elaw wrote:Yeah, right now I'm leaning toward the "weld on some tabs" solution. With my mad welding skillz combined with a MIG machine that cost almost $100.00, it should hold together for at least a week!

There should be very little load on the center bearing, unless your drive shaft goes ape shit out of balance somehow. :dur:

oil_me wrote:Is the center support bearing oriented with the dished side to the rear? I couldn't tell from the photo.

Yep, it is!

Here's a photo of the two driveshafts that are not in the car:

The one on the right is the one that came with the car. You can see the bearing is offset, with the longer mounting leg on the passenger's side. The one on the left is a 4KQ one, with a BMW bearing essentially identical to the one that's in the car (it's from a different supplier). You can see it's long leg is on the same side.

Here's another view:

In both photos, the bottom of the photo would be toward the front of the car.

The driveshaft that's in the car is identical to the one on the left in the photos, except it's maybe 10mm larger in diameter. I'm assuming that's an urquattro-vs-4KQ difference?

84 4KQ's had the larger driveshaft as well... 85-87's had the smaller driveshaft.