I have a 1993 240, automatic transmission.

It does not shift into overdrive until about 60mph or so, and only if I accelerate slowly (I know from the past that it should shift around 40mph if I accelerate slowly). If I accelerate quickly, it doesn't shift at all (or maybe it would at an even higher speed, but there's only so much that 3rd gear will do!).

I originally thought that it wasn't shifting into overdrive at all, because once I saw it wasn't shifting by 55mph, I got off the highway! Dealer and an independent Volvo shop that I trust (guy is factory trained in transmissions) told me it was internal to the transmission. This was before I discovered that it did shift at 60mph, so they didn't know that when they gave their prognosis. Solenoid has been replaced and checked. Relay has been checked.

Before I go back to the mechanic to tell him that it DOES shift, but at high speed, I'm wondering if anyone has any ideas. Maybe it's something I can do myself, like flush the fluid?

Thanks