Troubleshooting P0777 DTC

[jpowel29]

I am working through some bugs in getting my truck dialed in. My latest hurdle is coming in the form of TCM codes.

My truck has twice thrown the P0777 code. These have come under heavy acceleration and the truck shuts down around the 3-4 upshift and then the appearance of the CEL (I am currently running the stock TCM tune). I am able to drive home normally and the truck upshifts and downshift okay. Once I clear the code trans upshifts/downshifts fine under normal acceleration. Trans was given several weeks and a few thousand miles of highway driving before any racing, hard launches, or higher shift tcm tunes.

I changed the spin-on about 1,000 miles back and the fluid still looks clean, red and smells fine. The magnet had a very thin film of material on it (after a day of hard 1st and 2nd gear launches at the track). The Banks 6-gun does not detect any trans slippage or trigger any alarms prior to/after the DTC codes.

I have had the batteries load tested and the alternator is working properly. The trans has been in/out several times testing different torque convertors. I will change the spin-on again tonight and double-check the wiring connections.

Any thoughts??

 

[Mike L.]

I am working through some bugs in getting my truck dialed in. My latest hurdle is coming in the form of TCM codes.

My truck has twice thrown the P0777 code. These have come under heavy acceleration and the truck shuts down around the 3-4 upshift and then the appearance of the CEL (I am currently running the stock TCM tune). I am able to drive home normally and the truck upshifts and downshift okay. Once I clear the code trans upshifts/downshifts fine under normal acceleration. Trans was given several weeks and a few thousand miles of highway driving before any racing, hard launches, or higher shift tcm tunes.

I changed the spin-on about 1,000 miles back and the fluid still looks clean, red and smells fine. The magnet had a very thin film of material on it (after a day of hard 1st and 2nd gear launches at the track). The Banks 6-gun does not detect any trans slippage or trigger any alarms prior to/after the DTC codes.

I have had the batteries load tested and the alternator is working properly. The trans has been in/out several times testing different torque convertors. I will change the spin-on again tonight and double-check the wiring connections.

Any thoughts??

C2 clutch is coming on too fast while C3 is releasing too slow on the 3/4 shift. In other words it is a tie up ( 2 gears at once for a split second ). This usualy means an internal problem between the C2 and C3 clutch. I wouldn't be suprised to see bent splines on the P2 planet and C2 clutch hub. Keep the power down till it's fixed.

 

[jpowel29]

Thanks Mike. I will reach out to Dave on this one.

 

[duramaximizer]

We had the same problem, we set the trans to relearn and everything has been fine since. IDK what the problem was, mechant tore down the trans and found nothing. The only thing that we can think is that changing between big and moderate tunes seems to screw it up.

Relearn the trans and try it.