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Discussion Starter · #1 · (Edited)
I have a 2000 1500 w/ a 5.3 and a 4L60E. I had the transmission rebuilt 20k miles ago, about 400 miles post rebuild I ran into a 2-3 slip (same as before the rebuild), though mostly at low engine speed. The builder thought it was an electrical issue, I lived about 2 hours away and didn't drive it often (at the time), so I parts cannoned it - MAP, MAF, TPS, and eventually the computer. New comp gave a solid 10k miles of smooth and proper shifting so I thought that was that. Now I'm having the same issue again, with it also feeling sluggish off the line. I usually get either a laggy shift or a terrible slip (I'm talking RPM surge, no power while it tries to grab the gear) during 2-3 shift below ~2500 RPM, a sometimes lagging shift below 3500 RPM, and a usually noticeable lag or sometimes slip from 4400 RPM or more. Changing fluid didn't help. Noticed that putting it in tow/haul w/o hauling anything makes it shift a lot better under mid and hard engine load, no lag or slip. Under normal driving conditions the shifts are still better, still no lag or slip, just very hard (understandibly). What exactly does tow/haul do here that might be making a difference? I thought it just kept the converter locked and raised the shift points was all. After the computer change I figured the problem was electrical - now I have no clue
 

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Discussion Starter · #6 ·
I would check the line pressure with gauges to see if the pump was moving enough fluid.

Rick
I'll grab a line pressure gauge and try to check it over the weekend.

Do you know where the ground for the PCM or trans harness is on this? I wonder if I might just have a ground problem - the fuel gauge was reading empty when I got in the truck, but jumped up to 3/4 full as soon as I closed the door. Idk if any of those are the same ground as for the cluster though
 

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The powertrain control module has several grounds on the red connector and the blue connector. The wiring diagrams for this can be found at:

LT1Swap.com

Clean up your existing grounds or add temporary new grounds to see if that fixes the problem.

Rick

Sent from my SM-G965U using Tapatalk
 
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