I have a 1996, 5.9 12v, 47RE Trans (90% sure of this), with very high mileage and almost no history for the truck. When accelerating under light load, like going up a moderate hill empty, the truck has a violent shake around 20-25 mph. The truck also seems to not want to go into gear at low speeds when very cold, which leads me to suspect the front band being worn, but I'm having a hard time finding much information to support this theory.

A couple extra bits:

• The shake is so bad the aftermarket head unit will come out of the dash.
• "Pushing through" that speed seems to work. If I apply throttle until I get to ~25mph, then back off, the truck will shift gears and the vibration completely stops.
• I think the shake may be there even without load, but the truck glides through that speed range easily and it's almost imperceptible.

Anyone have thoughts on this symptom and it's cause? A local mechanic simply recommended outright replacing the trans without much other detail, and I'm trying to understand the root of the problem.

TIA

 

How is your fluid level and color?

Last time the filter has been changed and the bands adjusted?

Any codes stored in the PCM?

 

The fluid level is good. Right in the middle of the mark on the dip stick when hot, level, and running in neutral. Color is a little dark and certainly not the bright red of new fluid.

Filter was very recently changed, thinking it may help this issue but seems to have made no noticeable difference. I have no idea how long it'd been before this change but the filter didn't seem especially dirty to me. When doing that a portion of the fluid was changed but nothing flushed, just dropped the pan, swapped the filter, bolted back together and topped up.

I don't have a handy way to check codes, but could try an AutoZone or something.

 

During the fluid and filter thing- were the bands adjusted ? If so, correct specs for the diesel? Valve body bolts checked?

 

I did adjust the front band around the same time, and have again since the filter swap. I didn't touch the rear band, nor did I do anything with the Valve Body's bolts.