4l80E no reverse when vehicle heats up

[Jimbolya]

I have a 1045A2 with a 4L80E transmission. All gears/shifting works great in both forward and reverse when vehicle is cold. I gradually lose reverse (it slips) when it heats up. If I let it cool, all is good again.

It does have tranny hold back when put in first and letting off the gas at 25mph. Fluid is red with no abnormal smells. I have read that some people have encountered this problem on other vehicles and a few went away

when they installed a TransGo shift kit. I haven't pulled the reverse servo or dropped the valve body and really don't want to. ​

Hoping to throw this out there and see if anyone has any other ideas.​

Thanks.

 

[Action]

What is the fluid level when warmed up and shifted through all ranges and checked while the motor is running?
LIMP MODE would leave you in 2nd gear.
Have you checked for error codes?

 

[Dock Rocker]

Sounds like a broken seal at the accumulator or a cracked accumulator.


Sent from my iPhone using Tapatalk

 

[Jimbolya]

it is not in limp mode since it will shift 1-4 even with reverse slipping. Trans fluid level is in operating level when hot. Haven't heard of an accumulator being an issue with reverse. Thanks for the thought. I will research.

 

[Jon0249]

You have a bad output speed sensor. Easy fix. Just went through the same problem, back on the road in 2 hrs.

 

[Wire Fox]

it is not in limp mode since it will shift 1-4 even with reverse slipping. Trans fluid level is in operating level when hot. Haven't heard of an accumulator being an issue with reverse. Thanks for the thought. I will research.

Curious...did you ever find the actual culprit? I'm always wanting to know what little bugs show up in the 4L80E transmissions since I am troubleshooting a problematic one over time...