4L80E limp mode

[Bo Franzen]

Hi guys,
I have a 1997 Chevy van with a newly rebuilt 4L80E gearbox. It works through all gears but gearshifts are very harsh, almost banging in the next gear. And, when been driven up to working temp and engine turned off, when starting again the gearbox goes into limp mode, only reverse and second gear working.
If diconnecting the battery for about 10 minutes the problem goes away and I can drive hours if I do not turn of and off the engine. So I guess that the computer detects a problem in the gearbox, temp or mayby pressure and when turned off goes into the limp mode. Bcs, if going to limp mode while driving could really hurt the gearbox/Engine system.

Any ideas of where to start the search for the problem ?
I have connected a OBD-II scanner, but it detects no trouble codes, and with the simple OBD-II scanner I have I can not goes into any gearbox readings.

Help would be much appreciated !
Best from Bo in Sweden
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