You said the fluid was "good". Is it NEW?

It may be that the trans OD has tired O-rings that won't build up enough pressure to engage it. At least that was the case on a 4 sp/OD I had once (it would work only on cold starts). I changed the fluid and Bingo a restored overdrive. Transm fluid has seal conditioners and viscosity index improvers that break down with age so old fluid doesn't perform all its functions.

I have no idea whether the setup of an automatic OD would be vulnerable to this mode of failure. But if you have old fluid, changing it would sure be easier than pulling the transmission.

Ooh! Ooh! ---

You said the kickdown works for lower gears. But how aggressive are your shift points? The OD upshift would be the most sensitive to kickdown position. Your cable COULD be semi-misadjusted so that it permits the first three but is still tight enough to block out the OD shift. Try adjusting it.

Did this OD problem happen all at once or did it sneak up on you?

Good luck.

Doug Harvey

On my 91, the white wire broke just on top of the transmission, a few inches from where it exits the front of the shifter box. Of course if you have good 12V at the solenoid, this isn't it.
With all that stuff ruled out, you have a bad transmission. Sorry, but at least they're about the cheapest junkyard transmission on the planet.
--
Rob Bareiss, New London CT ::: '87 244DL/M47- 234K, '82 245T/M46-182K, '89 244DL/AW70- 212K Not too distant past: 86 244DL 215K, 87 244DL 239K, 88 744GLE 233K, 88 244GL 147K, 91 244 183K