Hello, I'm having an issue with a C6 I'll give you the history and then the issues. Just bought a 1978 F350 4x4 with a 429 for my sons first rig, the truck has been sitting since 2003 and started maybe twice a year, fluid levels we're full and drove the truck home around 100 miles, the only issue home was when it shifted into 3rd it would rev before engaging 3rd gear. I dropped the pan and valve body, cleaned both out, the valve body was pretty clean as was the pan, I installed a B&M shift improver kit, and torqued the band to 120 inch pounds and then backed off a turn and a half per instructions. New fluid added and test drove, shifts firm but still has a slight rev before engaging 3rd, changed the modulator and vacuum hose, still has a slight rev but I have not inspected the hose under the hood yet, now to the big issue. The tranny is nice and quiet until it gets hot, then there is a whirring metal noice while at idle and when in reverse the truck bucks pretty bad until a lot of throttle is added, when under throttle the noise goes away. It shifts into all forward gears fine with no bucking or shuttering, only shutters when in reverse under very low throttle like its still searching for reverse then bang when under throttle and the tires will smoke! Does this sound like transmission or torque converter going bad? I 've already checked for loose bolts on the converter..

 

3rd and reverse use the same drum (direct drum).

The flare into 3rd is happening because the band is released before the drum comes on, and the delay into reverse is also because the drum takes to long to apply.

Based on what you described I would have to say that the direct drum has too much clearance in the clutch pack most likely due to burnt or flaked clutches.

 

Thanks for the reply and info, sounds like you know these tranny's, are they hard for a backyard mechanic to rebuild? Any special tools required?