Wah Wah Wah in Overdrive

[Bisho]

I recently started getting a droning between 45-60 mph. It’s there when I’m essentially maintaining speed. If I’m accelerating or decelerating it not there. It goes away if I click off overdrive. Other than the droning, everything else is the same as it’s been the last 100k miles. It shifts fine. I’ve done a complete fluid exchange a couple times, most recently in the last 10k miles.

Am I getting ready to do a rebuild on the transmission?

 

[OEMGUY0720]

If the symptom is coming from the OD function, we can isolate the troubleshooting in that area first. If the mechanical aspect of the transmission appears to function as designed, you likely have a good transmission. I would assume there was no material on the AT drain plug/ATF when you drained it recently?

 

[Bisho]

If the symptom is coming from the OD function, we can isolate the troubleshooting in that area first. If the mechanical aspect of the transmission appears to function as designed, you likely have a good transmission. I would assume there was no material on the AT drain plug/ATF when you drained it recently?

Correct - no material. Isn’t the OD integral to the transmission?

 

[MongooseGA]

Do you have any clunking on/off throttle while at road speed?

My first thought would be to check the U-joints. They'll rumble or whine differently with different amounts of load on them, which might be the reason you feel a difference with OD on or off.

 

[Bisho]

Do you have any clunking on/off throttle while at road speed?

My first thought would be to check the U-joints. They'll rumble or whine differently with different amounts of load on them, which might be the reason you feel a difference with OD on or off.

I don’t get the clunking, but I do have a new set of ujoints waiting at home. I was thinking that OD on/off has a constant output from the driveshafts and would rule out ujoints, but now that you say that I suppose the load does change. I just can’t replicate the drone with OD off. I hope you’re right.

We’re headed home the next couple days from GA, so I’ll redo the ujoints and hopefully that does the trick.

 

[OEMGUY0720]

Correct - no material. Isn’t the OD integral to the transmission?

It is, and the OD switch is connected to an electric solenoid found in the valve body and can be serviced/replaced if that is indeed the culprit. I have seen a few threads from the 80 section that may share similar symptoms as yours.