Just did an engine change, bbc to sbc. Left the trans in the truck. Changed ECM and all that. The problem is it shifts hard from 1st to 2nd. Like the line pressure is maxed out. It was fine before the engine change. Changed the TPS to no avail. Is there any other vacuum/electronic gizmo that was on the sbc that controls the transmission 'cause I left all of it on there and hooked up the wires from the bbc wiring harness? Thank you
CK5
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4l80e
- Thread starter mykytiuk
- Start date
How about a little more info? What year is the truck? What year is the engine?
Thank you for responding!!! The truck is '94 K3500 Crew Cab and the engine came out of an '88 Burb 2500 that I installed about 18 years ago but was only driven about 7000 mi. since. I also installed, what I was told, an ECM from a '94 350 2500 4l80e truck. I also got from the wrecking yard a '94 350 throttle body and a few other misc. parts.
I had an issued with my 4l80e when I first finished my engine swap. The big connector in the drivers side of the trans was plugged in upside down. I'm using a tci harness though, not sure if the OEM plugs can be plugged in wrong.
Thanks again!!! Well I didn't disturb anything on the tranmission in an effort to avoid what is going on now. Thinking maybe the used ECM from a '94 350 4l80e truck might be the problem. I left all the vacuum/electronic gizmos on the on the 350 from the old Burb. Do any of those have any influence on the transmission? Any other ideas? Thanks!
mckustomfab
1/2 ton status
If I remember correctly there should be no vacuum hoses needed for the 4l80e, just the harness from the pcm.
could you swap the computer back and see how it does? I would guess you have something in that system ramping up line pressure. Be sure and check all ground connections, engine to frame, engine to body, battery to body and frame. If the engine was painted run a ground from trans to chassis as well.
Thanks for the help fellas!!! It turned out to be a bad knock sensor. I saw it indirectly mentioned a couple times in my research and thought why not try it. Still had the one from the 454, switched it and fixed the line pressure and the "service engine soon" light. Didn't know much about TBI engines before this project but I do now!!! Thanks again!
Cool! glad it worked out. It is perplexing that so many distant elements of the system can affect one another that way.
mckustomfab
1/2 ton status
Good deal!
