1999 V70 Transmission issues. Topic is solved

[SuperHerman]

Have a shop that knows about transmissions hook it up to their computer. You may have a failing solenoid. The 4 speed tranny is pretty robust. Many people have had great luck changing the transmission oil a few times, but parts fail so your case may be different.

Throwing out ideas, other than a flush or drain and fill, may not resolve your specific issues. Flush and/or drain and fill has a very high success rate on the 4 speed. Not so much on the 5 speed as it suffers from gunked up solenoids. The smart approach is to have a competent transmission shop do an examination with their computer where they can watch what the solenoids are actually doing.

Now if your first flush showed signs of high levels of metal you may have a mechanical issue.

[Twopointfourturbo]

No, the first oil flush just showed the usual darkened trans oil but no metal as far as I or the garage could tell. Do faulty solenoids have a tendency to fail when the trans comes up to temp? That might explain why, after the first garage, we had no problem driving on normal roads but then again problematic at highway speeds...

[Twopointfourturbo]

Final update: got the car to an auto trans specialist who replaced a faulty 4th gear assembly. Car is running fine again!