I had a problem with the driveshaft causing a thumping sound under acceleration. I could move the shaft about a quarter inch within the support bearing and duplicate the thumping sound. So I replaced both the driveshaft support and the bearing, being careful to ensure that I marked all relative positions so I didn’t install it out of phase.

When I test drove the car, the thumping sound was cured. But now the driveshaft shudders when accelerating from a standing start. It doesn’t shudder any other time, even when accelerating at speed or going up a hill. Once I get going, it smooths out.

I’m wondering if there’s some critical adjustment I need to make to ensure alignment There’s a spline joint that I had to take apart to get the bearing off. The spline pieces went together and are held in place by a set screw. The slack is taken up by the drive shaft flange at the transmission, which has some float or play. I put all the pieces back exactly as they came off.

Could I have installed the bearing crooked? Or do I need to follow some procedure to readjust the spline or location of the support assembly?

I’m at wit’s end and would appreciate any advice!

Robert

Hello Robert:

There is a Volvo TSB on this very topic! What you need to do is to shim up the carrier bearing stage (the part that bolts to the body). Try up by 1/2" (washers between the stage and the bearing housing) or down by a 1/4" (washers between stage and body) to begin with. This is a trial and error procedure, but it isn't hard. These cars are very sensitive to driveline alignment...

It worked well on my '89 760...

Good luck!

Herb Goltz, London, Ontario, Canada '89 760GLE w/161K mi

Thanks, Herb!

I'll try that. I have the Popular Science Alldata CD that has TSBs. I found three TSBs related to drive shafts (or propeller shafts), but none mentioned alignment correction with shims. Do you happen to know the TSB number?

There were a pair of washers between the carrier bearing stage and body at each of the four bolts. I put those back. There also was a flat bar spacer between the stage and support bearing. I'll experiment with those two variables to adjust the height and see what it does.

The only thing I saw in the TSB's I have is that the two shaft components have to be in line. I can check that with a level, I guess, to determine whether to move the support bearing up or down. I'm wondering, though, if it makes a difference whether the car is resting on the rear wheels or on a jack support somewhere. I don't have any way to get under it with it resting on the wheels. Any ideas? Is that important?

Robert

my 94 944Se does the same thing
it shudders at takeoff, but only if the car has more than 2 ppl in it,
or if it's loaded down.

Your drive shaft is dynamically balanced. that is why some of the flange bolts are longer than the others. You should have marked the position of each bolt too. Sorry.

How are the U-joints? If bad, change or grease them. If good, get thee to a driveshaft specialist who does dynamic balancing. Did a weight fall off while you were messing with it?

I made sure that the bolts at the rear end went back in the same holes, along with the spacers (or whatever you call the thing that mounts like a washer but holds two adjacent bolts). I didn't think to match the four cap screws and nuts that hold the front to the transmission flange.

In any case, the shudder feels like it's in the rear, not the front of the shaft. No weights fell off. If it were a balancing problem, wouldn't I have symptoms at other times besides a standing start?

I did check the joints while it was out. Absolutely no play in them.

If the total length of the drive shaft were incorrect because the two pieces didn't overlap enough or overlapped too much before the set screw locked them in place, could that cause this problem? If so, how to determine the correct length before tightening the set screw?

???????

Robert

You are over my head. I really think a Driveshaft specialist is in order. Where do you live?

I'm in Chattanooga, Tennessee. There are two entries in the yellow pages for drive shaft service. One is for an individual who's been doing driveshafts for about forty-five years. He's the one I took the shaft to after I removed it from the car so he could replace the press-fit bearing and support. Even with all his experience, he scratched his head and said he'd never seen a drive shaft like this one. Figures...

Anyway, you'd think with his experience he would have installed the bearing correctly. I'm thinking an alignment problem on installation but can't imagine what it would be.

Make sure you check out this Volvo TSB:

Driveline Take-Off Vibration: Shimming May Be Required. From Volvo Technical Service Bulletin 45/102 Jan '91. [Symptom:] Take-off vibrations at low speed, especially with high acceleration and/or heavy load, can occur in some cases. [Solution:] The level of vibration can be reduced by changing the vertical position of the center support bearing. Best results differ from car to car. Start with a change of 6mm (1/4") upwards. If results are not acceptable, try positions from 5mm (3/16") downwards to 12mm (1/2") upwards from the original position. Note that clearance between drive shaft and fuel lines must be at least 20mm, and between drive shaft and the fuel tank at least 16mm. Shimming upwards should not exceed 12mm (1/2") and after re-positioning the center support bearing housing should not contact the floor pan.

Thanks. This sounds like it's probably the answer. My symptoms exactly.

Now I'm wondering if I just spent the price of a replacement support bearing needlessly. I'll give it a try.