Trans wiring help... Experts/Techs nneded...

I have transplanted a LQ4 6.0 liter out of a 2000 GMC 2500 4x4 into my 1991 GMC Syclone. I have the original wiring harness and computer hooked up. I am using HP Tuners for tuning also. The Engine is hooked up to my 1995-1996 built 4L80E trans. I am not using the original 4L80E trans the engine came with in this build. I do not have it. Anyway, I thought I had everything hooke dup correct but the trans is in 2nd gear and will not shift while driving. I guess it is in default mode. I have checked all the wiring from the main connector and the two little ones at the trans and they are all fine. I am missing something little I am sure but can not figure it out. I see in the pin out that there are like 4 other wires at the ECM that are not being used. Labeled like PRND A Input, PRND P Input, TCC Brake switch, PRND B Input. Anyway, I was thinking the 2000 truck it came out of must have another sensor elsewhere I do not have or something like that.

Any ideas?

It will go right into Reverse and drive without a problem. Just will not change gears while driving, stays in 2nd. :(

Thanks
Will

I always have to ask this question... are you sure the tune you have is for an 80e transmission? A 60e tune will not work. If the the harness is a 60e harness, yes it will hook up but the wiring is wrong. Do you have two speedometer type hookups connected on the transmission?

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Originally Posted by _Syclone_

I have transplanted a LQ4 6.0 liter out of a 2000 GMC 2500 4x4 into my 1991 GMC Syclone. I have the original wiring harness and computer hooked up. I am using HP Tuners for tuning also. The Engine is hooked up to my 1995-1996 built 4L80E trans. I am not using the original 4L80E trans the engine came with in this build. I do not have it. Anyway, I thought I had everything hooke dup correct but the trans is in 2nd gear and will not shift while driving. I guess it is in default mode. I have checked all the wiring from the main connector and the two little ones at the trans and they are all fine. I am missing something little I am sure but can not figure it out. I see in the pin out that there are like 4 other wires at the ECM that are not being used. Labeled like PRND A Input, PRND P Input, TCC Brake switch, PRND B Input. Anyway, I was thinking the 2000 truck it came out of must have another sensor elsewhere I do not have or something like that.

Any ideas?

It will go right into Reverse and drive without a problem. Just will not change gears while driving, stays in 2nd. :(

Thanks
Will

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do you still have the original wiring harness for the engine and tranny thet came in your truck?
if so you will need to compare the plugs for the tranny. i was having a simular problem.

i had 13 wires in my factory tranny plug and only had 12 in the plug in the harness i used for my swap. i had to re pin thre tranny plug using my old harness as a guide. the colors are the same just make the new look like the old and it should work.