Newly rebuilt 4L80E shifts funny

[rlb]

I'm looking at buying this truck to fix and sell. Its a '95 K3500

" I believe that there is some type of electrical gremlin, outside the transmission, that is keeping the transmission from operating properly. The truck does run, and moves under it's own power. Sometimes the transmission shifts like it should. Sometimes it goes into "limp - in" mode. I am basically tired of chasing my tail on it, and think that it needs to have a new home. "


Any ideas? I have the FSM at home so will go through that tonight. I might make an offer on it tomorrow. If I can fix it without too much fuss or expense I could sell and make some $$

 

[Will L.]

My hummer had that problem on and off for some time. Finally found I had pinched a wire in the tranny with the pan at some point. A little paint on electric tape as a temp fix until I could order the replacement harness. Umm, now that I think about it, I might never order that harness- 25,000 miles later and not 1 miss since.

 

[rlb]

My hummer had that problem on and off for some time. Finally found I had pinched a wire in the tranny with the pan at some point. A little paint on electric tape as a temp fix until I could order the replacement harness. Umm, now that I think about it, I might never order that harness- 25,000 miles later and not 1 miss since.

Hmm

So the wire was IN the pan? The guy wants $1200 for the truck and it looks okay otherwise. I could prob sell it for $2500

 

[Will L.]

That was my problem, there are lots of others that could cause it...
I'm just saying one thing to check. $1300 profit for maybe a rebuild 4l80e? hmmm
I lived in Vegas most my life- I am not much for gambling...

 

[THEFERMANATOR]

When it goes into limp mode, pull the codes and see what comes up. It could be a simple issue, but knowing the codes will help.

 

[vegtech]

I have a a couple like this. One had a bad ignition switch the other had a broken wire at the round connector on the side of the trans. It was the yellow wire that provides power to the solenoids. I Googled 4l80e shift problems and found a wire diagram and test procedure for everything in the trans, done from the outside.

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