hearing & feeling a slight ??? thump? clunk? between shifts (lower gears)on our 99 V70 XC AWD (auto) w/70k had a volvo mechanic check it out. He found nothing that he could attribute to the problem. It doesn't always happen under accelerated shift...seems to be when it is?????? It can happen when driving 55 mph and going up a hill....but also happens at 30 mph in the middle of a village...but never consistently. Mechanic told us to try changing trans fluid...although it wasn't very dirty...plan on doing this tommorow. can anyone offer any suggestions/insight/ideas??? COuld this be the start of something major? any information shared will be appreciated.

Sounds like it is happening with the torque converter lockup happens, and I'd bet that the transmission fluid change will cure it. The 98 - 00 V70XC cars seem to really like trans fluid changes about every 30K or so miles to eliminate harsh shifting and harsh converter lockup.

Converter lock-up??? If you have more info to share on this i would be grateful. Thnaks you for your response

Not sure I understand your questsion norEast, so apologies if this reply is just way off base...

All modern auto transmissions have the ability to "lock" the torque converter so that there is no ineffeciency lost to the normal slippage of the fluid coupling, they use a clutch mechanism inside the converter. Almost always, this is software controlled.

Just a fuel mileage thing, lock the converter to get a solid coupling between engine and transmission when the slippage of the fluid coupling isn't needed.

You can see this happen by watching the tach as you reach a steady speed, engine revs will fall as though a gear shift has occured, even when the transmission in already in 4th gear. On the Asian-Warner transmissions used in Volvos, it almost has a CVT-like effect -- they do a nice job of gradual lockup rather than sudden.

Wondering how a torque converter works, found this link on google:

"http://auto.howstuffworks.com/torque-converter.htm"

Thank you for the useful info --- The transmission oil change seemed to do the trick. The volvo mechanic told me volvo has no transmission schedule for oil change, but he recommended it should be done at about every 30k.