6l80 won't shift at WOT.

[Hartley]

I have a L77 6.0 w/6l80 out of 2017 Caprice police car with 20k miles on it swapped into a 56 Chevy. I put a trans tune out of the Tuning School trans guide. Car seems to shift better than before (It shifted very soft before) , but at WOT it won't go in gear. It sounds like it bounces off a rev limiter at 6000. I raised rev limiter to 6500 and lowered the WOT shift to 5500 rpm to see if would shift, but it still cuts out at 6000rpm and won't go into gear until I lift off throttle. Put a scan on it and I noticed the trans output shaft reads 0 rpm. Does that mean the sensor would be bad? Doesn't have very many miles on it. I'm new to this so I just want to make sure I'm not missing something on the tuning side before I go and pull the valve body to change the sensor. Any advice would be appreciated.

[Alvin]

It's going to shift by speed first. When you tried to lower the WOT shift points did you adjust the shift speed also? In the full throttle tables and also in the part throttle tables.

[Hartley]

Thanks for the response. No I haven't tried that. I'll give that a shot this evening and see if it changes anything.

[Asd_srt]

I have a L77 6.0 w/6l80 out of 2017 Caprice police car with 20k miles on it swapped into a 56 Chevy. I put a trans tune out of the Tuning School trans guide. Car seems to shift better than before (It shifted very soft before) , but at WOT it won't go in gear. It sounds like it bounces off a rev limiter at 6000. I raised rev limiter to 6500 and lowered the WOT shift to 5500 rpm to see if would shift, but it still cuts out at 6000rpm and won't go into gear until I lift off throttle. Put a scan on it and I noticed the trans output shaft reads 0 rpm. Does that mean the sensor would be bad? Doesn't have very many miles on it. I'm new to this so I just want to make sure I'm not missing something on the tuning side before I go and pull the valve body to change the sensor. Any advice would be appreciated.

Happen to have a log of the shift hitting the limiter? Remember the 6l80s can need some lead time sometimes to get to shift right.

[mercrising]

Any luck here guys. I am in a situation fighting some WOT no shift issues on e67 and t43. These ECU's were manual GMPP controllers first, now paired with t43 6 speeds, but don't want to seem to shift at WOT with a variety of attempted RPM and MPH settings. Shifts OK part throttle.

Best we got in the few minutes I was able to stop by, was an OK 1-2 shift. Still can't get into 2-3 at wide open throttle, and it noses over hard like a limiter. I've checked the "cold start" limit table, TQ MGT, and they all appear to be set above where our issue occurs about 5900-6000.

Won't be back to the truck until at soonest Friday but, curious if you got it worked out?!

[TheMechanic]

Had a similar problem that I discovered. Different trans but might be your problem.
https://forum.hptuners.com/showthrea...ht=rev+limiter

[mercrising]

Found issue to be the Spectre 90 elbow into the TB, coupled with factory land cruiser air box and filter, was collapsing. Not a ecu or trans cal issue at all.

[Hartley]

I've changed WOT shift speed points and timing and nothing has changed. Still cuts out around 6000rpm. My issue might be the air intake too. I have Spectre 90 elbow also and I don't think I'm getting enough cooler air to the filter. The scanner shows the intake air temperature too hot. The 56 Chevy engine compartment is pretty sealed up. Planning on building a insulated box around the filter and cut a hole through the core support to get direct air to it I was working on fixing the transmission problem 1st, but after reading the mercrising post, it might not be the transmission after all. The other thing that bothers me tho is when I run the scanner, the transmission shaft output sensor RPM reads zero. The input side reads correct. I replaced the input/output speed sensor above the valve body. Still reads zero on output RPM. I'm not sure what else would be causing this? I don't want to screw something up in the transmission.

[mercrising]

Post the logs and file.

Mine was mechanical no doubt about it.

[bignick]

y'all ever figure this out?