My truck is a '91 with 5.0 and AOD. When the transmission shifts when accelerating through about 35-45mph, it settles into (overdrive??) roughly. Not a smooth change, but a "clunk". Truck has done this for probably as long as I have had it. Normal? I don't know if the previous owner added a shift kit... or how I'd tell just by looking.

The truck goes into reverse smoothly, and all other gears are fairly smooth when moving forward with the exception of this one.

Tranny fluid is still bright red, but is due for a change (I do it every 36k, minimum).

Thanks again,
-Mike

 

if it has a shift kit it will shift hard into all of the gears not just overdrive