Volvo: 2000 S80 Volvo Transmission high rev, mobile 1 synthetic oil, volvo transmission

Question
QUESTION: Just did a tranny flush with mobile 1 synthetic oil at 120K miles, the rev seems high 2500rpm cruising at 70 mph. The first time I did the same flush at 90K, the rev was 2000rpm cruising at 70mph. what do yu think its the problem this time?
Thanks for your advise

ANSWER: Lawrence,
Sounds like the trans is not shifting into the last gear or the lock up torque converter is not locking. The Volvo scan tool in the montior position should show what gear and if going into lock-up. There are solenoids that control that. I would suspect there are also fault codes listed.

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QUESTION: There are no fault codes message showing, I don't suppose not changing the ATF filter is an issue? If what you suspect is true, does it means it's time for a new tranny?

Answer
Lawrence,
I think what you are telling me is that the RPM's at 70 have increased over time. That being the case I would say the trans is not shifting into lock-up or maybe not into 5th gear. If you need to verify that as a problem find a shop that has the Volvo scan tools and let them test the trans with the scan tool and monitor the shifting and verify if the trans is going into lock-up. Right now it is hard to say if the trans is at fault or is there a saftware problem in the control unit.