Slipping Out of OverDrive - Not From 6th to 5th

[skydancer147]

While driving at speed anywhere from 62-75 mph, my 6th speed allison seems to slip out of overdrive no matter if I am under load or not. The sensation felt is not a down shift and seldom lasts from more than 1 to 2 seconds (and only occurs when going up hill or putting more of a demand on power) before catching up to itself. It will do it either in or out of cruise and with tow button on or off. This problem does not appear while driving regular every day operation on mostly flat roads with minimal grades and may not show up for days. Fluids and regular servicing is all kept up. Vehicle tows about 90% of the time for about 10-12 hours a day. This sensation did not start appearing until about 240,000 miles. I currently have 290,000 miles and everything is still working good otherwise. Just worried about potential problems down the road. What do you think is causing this?

I have been told by some that it is a torque converter related problem, but I can't seem to pinpoint or get good advice - ANY would be helpful.

[OneRVer]

Could by any chance the fluid be a little too high. I have been told by allison to run the fluid between 1/2 quart low and the full mark. Transmission oil will foam and cause weird problems. Just a thought. Please keep us informed. Good luck.

[skydancer147]

Thanks for the reply. I check my fluids daily and maintain "full" either hot or cold as indicated on the dip stick. However, your suggestion is logical and therefore I will try running a quart low and see what happens. Thanks again~

[94-Newmar]

Sure sounds like Torque converter lockup engaging/disengaging.