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Hey guys, my buddy and I just rebuilt my 4L60E out of a 1999 tahoe. After reinstalling everything we finally put it in gear. Reverse first,not much movement... thinking there is air in the system we drove around for about 20 min. Still no power in reverse, just slipping. We hooked up a scantool and found 2 issues. First, the computer does not recognize Rev as a gear selection. P/N is correct and O/D, 3,2,1 all list correct on the scan tool. In reverse the scan tool shows a p/n gear selection.
Second issue is that line pressure is ~ 80 psi no matter what. Park at idle,or under acceleration and all gear selections. No change in line pressure.
With the scan tool we tried to test the PCS and no matter the amperage,line pressure remained constant.

Any help??
 

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Hey guys, my buddy and I just rebuilt my 4L60E out of a 1999 tahoe. After reinstalling everything we finally put it in gear. Reverse first,not much movement... thinking there is air in the system we drove around for about 20 min. Still no power in reverse, just slipping. We hooked up a scantool and found 2 issues. First, the computer does not recognize Rev as a gear selection. P/N is correct and O/D, 3,2,1 all list correct on the scan tool. In reverse the scan tool shows a p/n gear selection.
Second issue is that line pressure is ~ 80 psi no matter what. Park at idle,or under acceleration and all gear selections. No change in line pressure.
With the scan tool we tried to test the PCS and no matter the amperage,line pressure remained constant.

Any help??
Does it shift gears when it was moving?

Try very fine adjustments on the shift level at the side of the big external switch box on the drivers side of the trans. These tell the computer which gear is selected. The computer needs to recognize reverse as well as all the other selections.

Also, warm the beast up and shift it into gear then out a few times then check the fluid level with the engine running at normally warmed up operating temperature. Don't go out and drive, that will cause damage if all it has is 80 psi of line pressure in any and all gears.

Bogie
 

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Did you replace the electronics in the trans during the rebuild process?

Mayb a faulty PCS
 

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The EPC (electronic pressure control solenoid) is probably faulty and not responding to input from the TCM.

Also, if the transmission is not going firmly into reverse, or slips in reverse, the most likely culprit on a fresh rebuilt unit is a cut sealing ring on the pump stator. What type of sealing rings were used-scarf cut, or 1 piece teflon? Did you use a resizing tool on the sealing rings to insure that they would seat inside the drum without damage??? It's very easy to damage the sealing rings when putting the pump in. When you put the low/reverse piston in the bottom of the case, did you put new sealing rings on it as well?

Lastly, if the vehicle is starting in "N" and "P" as normal, the switch is not likely to be your problem. Further, if it is shifting through the forward gears normally when driving, the MLPS, or NSS, is not your problem.
 
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