4L80E torque converter question/ concern

[t93k2500]

So I put a 100 mile round trip today on the truck (in sig) with cruise at 60 (2100 rpms). When the right lane merges with an on ramp, I move over, take off cruise and speed up to 73 (2500 rpms). All is normal and I maintain this speed for a while until I notice that the tc seems to be constantly locking and unlocking, jolting between 2500 and 2700 rpms, and continues to do so until I slow down under 70 (below 2400 rpms) Truck has 4L80E with 157,000 miles, and has never complained at all. Any input on this issue is appreciated.

 

[t93k2500]

Nothing at all?

 

[Crummins]

Iirc, there is a solenoid that tells the converter to lock up. That solenoid might commanding unlock and lock again and again.

I had almost the same issue with one of the shifting solenoids, while travelling down the freeway it would command an upshift and quickly the transmission would downshift again. This kept repeating. When we hooked it up to a computer we saw that the engine computer was not commanding a shift so we replaced the solenoid and all was better.

I would say get it to a shop that can watch what is happening and go from there.

 

[t93k2500]

Iirc, there is a solenoid that tells the converter to lock up. That solenoid might commanding unlock and lock again and again.

I had almost the same issue with one of the shifting solenoids, while travelling down the freeway it would command an upshift and quickly the transmission would downshift again. This kept repeating. When we hooked it up to a computer we saw that the engine computer was not commanding a shift so we replaced the solenoid and all was better.

I would say get it to a shop that can watch what is happening and go from there.

Thank you, I just ordered an ALDL cable so I'll be able to start datalogging and hopefully uncover the issue.