no overdrive

[jd mech]

I have a 95 gmc k2500,6.5t, 4x4, 140000 with a 4l80e. Was driving home home and tranny seemed to be shuttering. Floored it, trans downshifted and when trying to shift to overdrive it acted as if in two gears at one time. Finally there was a bit of a bang and trans shifted to overdrive. I came to a stop 3 times and everything worked great, including torque converter locking up and unlocking. Let it sit for a few hours and tried it again. Would not shift into overdrive but torque converter appears to be locking and unlocking. Connected my scanner and showed code 68-trans component slippage. Anyone have any ideas?!

[grancito]

Here's a long shot. Could be a bolt in the valve body come loose. Happened to my 82 chev, caused two gears to partly engage, heated the fluid and blew a lot out, and the clutch particles caused partial sticking of the shift valves, leaving only gears 1,2,3.

[95suburb]

how can you tell when your torque converter locks and unlocks?

[JD_countryboy]

Dump a bottle of lucas trans fix in your tranny. Bandaided my slipping tc long while back, till i got time to rebuild it. Stuff works, if its not a mechanical problem.

To test tc lockup, while cruiseing just barely touch your brake pedal, enough to make brake lights turn on. If tc is locking/unlocking, you will hear a small engine rpm increase, and barely feel what feels like a shift. Let off brake pedal and should shift back up.

[jd mech]

So I checked all electrical components. They all checked good. Pulled valve body and despite flushing tranny twice valve body was full of tiny particales of clutch material so cleaned that up. Put it back together and still no od. So I broke down and bought a reman tranny, used a buddies two post lift and installed myself. Come to find out it didn't have orginal tranny in it with just over 140000 miles (kinda surprised). Also installed new ss diesel supply pump. Tested it out and I finally had overdrive!!! Raced my brother with 04 dmax (on stock setting lol) and to my amazement the ol 6:5 kept up!!!! Should mention I have marine injectors, mechanical wastegate, 4in exhaust, and a kennedy diesel chip.