high speed rear end of car bumps around

hankeester · Post by **hankeester** » 03 Jun 2010, 13:45

I've got a 99 v70XC 170K miles and have a jarring/bump going on at high speeds. It's almost like I've hit a bump in the road plus the rear end hops somewhat. It's nothing too violent just feels like a little left to right or right to left action going on. I can't hear any noises with the windows up or down although I'm travelling at a high rate of speed. There's no other symptoms such as clunking when shifting into reverse or forward gears.

I've read some possibilities are: torque converter, bevel gear, tranny software upgrade, visicous couple (although I doubt thats the issue) or possiblity just needs tranny flushed/filled.

My u-joint in the drive shaft is going out and was wondering if that could cause the bump/jerky motion at highway speeds.

I've only had this car for 3 months. It's in good shape exterior/interior wise and bought for 2500. I've got 300 into for a valve job and 70 into a upper motor mount. I will need to replace throttle module down the road (it's on its 2nd one and out of the recall window) but will use the canadian company instead of another volvo module which will fail again.

Thanks

Post by **JRL** » 03 Jun 2010, 14:02

hankeester wrote:
I've read some possibilities are: torque converter, bevel gear, tranny software upgrade, visicous couple (although I doubt thats the issue) or possiblity just needs tranny flushed/filled.

My u-joint in the drive shaft is going out and was wondering if that could cause the bump/jerky motion at highway speeds.

Thanks

You posted on XC70.com and already got a lot of answers.
Your description makes it hard to diagnose but it could be the propshaft, the torque converter in the tranny is my bet, possible V/C ( but I doubt that ), same with a tranny flush in itself (but it should be done anyway).
The B/G should not make a thump noise if bad.
If I could feel it, I probably could tell you in 5 minutes what it is as I've had them all!

hankeester · Post by **hankeester** » 03 Jun 2010, 14:33

thanks JRL,

Just thought I'd post over here to expand on the possibilities. BTW, apparently it wasn't the heater switch for the seat as it's not getting warm (remember I bought one from you?). I'm taking it in for diagnosis on Tuesday. After they figure out what is wrong I'm gonna have them drop the driveshaft for the summer, order a new one before winter hits.