QuestionQUESTION: Hi, I recently purchased a 2004 Volvo v70R, which has a vibration that is difficult to pinpoint, but seems to be coming from the rear passenger-side wheel. The vibration only occurs between 65-70 km/h (40-44 mph).
When I test drove the car prior to purchasing it, there was no apparent vibration at any speed. However, when I picked up the car from the dealership after having some work done to it prior to purchase, the car exhibited vibration at the speeds noted above.
The only differences in the car between the test drive and my picking it up after purchase were: a new set of summer tires was mounted on the original Pegasus rims and the passenger side seal on the bevel gear unit was replaced (which I think required removal of the front axle?).
At first I assumed that one or more of the new tires was misbalanced, but I subsequently purchased a new set of peg rims and I got the new tires mounted on those and the vibration remains. New winter tires on the old pegs also vibrate.
It's a 6 speed manual, and there is no difference if the car is in gear or in neutral, or whether I'm on or off the gas.
After reading a few forums, I had a few suspicions as to what it could be: an unbalanced driveshaft/propellor shaft, bad CV or U joint, bad wheel bearing, bad brake caliper, bad engine mount(s), bad viscous coupler.
I was thinking of dropping out the propellor shaft to see if that makes the vibration stop. If not, then I would assume it's either the bearing, CV joint or viscous coupler. However, I'm not getting any clicking, grating or squealing from the rear end, so I'm not cofident that it's any of those areas.
Any thoughts on what is the most likely culprit and/or how to diagnose?
Thanks,
Jeff
ANSWER: Jeff, when it's that speed specific, it's almost always a balance issue with the tire or rim. It sets up a harmonic shudder because it's out of balance. That and the fact that the tires were changed since the smooth test drive screams to me wheel balance. Maybe try a different shop to do the balancing?
What is a bevel gear unit? A differential?
Mark
---------- FOLLOW-UP ----------
QUESTION: Mark,
The bevel gear is what Volvo calls the angle gear or front differential.
I don't suspect the tires or rims at this point, as all of the following configurations exhibit the same vibration at the same speeds:
the new summer tires on the old rims;
the new summer tires on the new rims; and
the new winter tires on the old rims.
I suppose both sets of rims and tires could be damaged/unbalanced, but I would expect that there would be some variation in the intensity or speed at which vibration occurs.
With respect to the bevel gear/angle gear/front differential seal replacement, would the front axle or the driveshaft have to have been removed to replace that? I understand that Volvo uses different lenght bolts to balance the driveshaft from the factory. Do you know if such bolts would have been taken on and off during replacement of the seal? If so, I suppose that they could have been replaced in the wrong position, thereby unbalancing the driveshaft.
Thanks,
Jeff
Answer Jeff, excellent response, thank you!
the new summer tires on the old rims;
the new summer tires on the new rims; and
the new winter tires on the old rims.
You are correct, this leads us away from the wheel issue.
I understand that Volvo uses different lenght bolts to balance the driveshaft from the factory. Do you know if such bolts would have been taken on and off during replacement of the seal? If so, I suppose that they could have been replaced in the wrong position, thereby unbalancing the driveshaft.
I am embarrased to say that I was unaware of that if it's true. Never been an issue for me. Put the bolts back from whence they came. Simple. It is a possibility though. They should have marked it before removal.
I "balanced" a replacement Jeep flywheel by adding washers to the appropriate flywheel bolts until it behaved. It was a nuetral/zero balanced motor that I was unaware of. O/wise, I would have had the flywheel zero balanced BEFORE installation. Thank you mister customer for the lack of sharing critical information.
Anyway, It is a distinct possibility. I would return the vehicle to where the repair was perfomed and make them make it right. Those bolts WERE taken off and the driveshaft removed and reinstalled. What a hoky way to balance though. Why not just balance the shaft itself? Duhhhh....
Mark
