4T45E Logging/Tuning

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I recently bought a VCM MPVI Pro that I’ve had just under a week. One of my first major projects is to use it to troubleshoot a stock 2000 Pontiac Grand Am GT that we own.

Here’s a bit of the background of what’s going on. A few months ago I changed out the transmission fluid and filter, every since then the transmission under WOT or heavy load has issues. It will downshift, but the RPMs jump up and down and up and down while accelerating (about 500 RPM jumps).

What I would like to do is datalog the vehicle while this is going on to try and pinpoint the issue. My question is what PIDs/Datapoints would be the most helpful in troubleshooting a 4t45e transmission? I have a suspicion that the problem is pressure related and maybe I can tune the issue out.

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Last night I finally got a little bit of time with the car. I performed my first datalogging with the MPVI Pro on a 15 minute trip to a restaurant. The first thing I noticed is we were cruising down the highway and the TCC mode was “off” the whole trip. Speeds were around 60 to 65 MPH. On acceleration the shift time errors were in the 6 second range. There were no DTCs.

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when you drain the fluid and put new fluid in, new fluid has detergents in it that break up crud... now the valve body is sticking...

time for a rebuild

Oh well, I had a strong feeling that was going to be the answer.

Thanks!