My 1990 240 sedan w/215k automatic seems to coast in drive. Driving on the level freeway at 65mph, let off the gas, and the engine slows to idle while the car is "coasting" at high speed in overdrive. Step on the gas again and when the engine rpm,s catch up to your speed, the car accelerates. There are no other drivability problems. The transmission works fine in all other respects. The trans fluid was just changed and is full to the d.s. mark. It behaved the same before the change and after. Has anyone had this "phenomenon"? Is it a sign of something bad coming? Thanks in advance.

You have noticed a problem. The auto box is not supposed to allow the engine to return to idle at such speeds, the rear wheels should drive the torque converter through the overrunning clutch, or sprag as it is also known. Have a good trans shop test drive the car, but it sounds to me like the trans is going to come out of the car.

Please excuse me if I'm asking a stupid question but what did you expect to happen?

Cheers

I have this happen occasionally on my old 245 with a manual transmission with overdrive. If your transmission has overdrive, that could be the problem. I've read here that overdrive units can be fixed with a new seal kit and/or a fluid change. That may not be your problem however. Good luck!