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ECM commanding max line pressure 2nd gear only

kansas-farmer
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kansas-farmer New Member

kansas-farmer

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Posted

Good morning all,

Brand new to this forum, so thanks for taking some time to look this over.

To the point:

We are working on a 2004 GMC Sierra 1500 4x4 5.3 4l60e 4 door. 149600 miles.
Complaint:
Reman transmission shifts harsh 1-2 and 2-3.
Transmission TAPS will not adapt
Desired PC solenoid duty cycle in any gear except 2 is 55% at idle
Desired PC solenoid duty cycle in 2nd gear, either manually shifted or in drive under normal operation is 8%
The PC solenoid is responding properly to the request.
All shifts related to 2nd gear are done under max line pressure per PCM request.

Answer needed:
What the hell is the PCM thinking? Why is it thinking this and how the hell do I change it's mind? We don't need 200 lbs of pressure in 2nd gear.

Conditions and timeline of repairs:
5.3 leaked oil, rear main and pan gasket.
Transmission reluctant to hit reverse, shudder in 3rd. All other shifts ok, trans oil getting dark quick under normal operation. It was decided to reman the transmission when it was on the ground for the rear main seal. Transmission pulled at 149500 miles.
The reman is abit tougher than a stock 4l60. It as the better clutch disks, better sprags, hardened shell, billet servo, and the wide band. Trans shop that did the work also agrees with my assessment that up-shifts related to 2nd gear are too harsh. 2 scanners reading the same. Both scanners cleared TAPS and show no adaptation. Both scanners read a PCM command to go to full line pressure when the transmission is in 2nd gear.

What's the fix? Ideas??

Thanks a million in advance!!
Kansas Farmer

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