78Chevyc10

I recently purchased a 1972 Nova, with a 5.3 in it. It has a th350 with 3.73 so I want to put an overdrive in it. The car has a stock 1999 computer, but the problem is that the wiring for the transmission has already been deleted.
Is it easy to add the wires to the computer?
Will I have to find the transmission harness from another harness, or do they make harness so I can buy it?
Any help is appreciated!
Thanks!

brandon6.0

iTrader: (32)

best thing to do is get another harness out the junk yard from a 2500 Silverado. Thin make it standalone your self. Look on lt1swap.com he has a complete diagram to make a standalone harness. Or u could spend the money on a psi harness.

brandon6.0

iTrader: (32)

this guy says he just purchased a psi harness for his setup trying to narrow down an issue he was having. He may want to sell his other standalone harness. Would hurt to ask.

https://ls1tech.com/forums/pcm-diagn...-bad-tune.html

78Chevyc10

Thanks for the input. Will the computer itself still work and will the 2500 harness plug right into it?

brandon6.0

iTrader: (32)

yea the computer should work as long as u get a harness to match as in colors. red/blue. The newer 03+ PCM are blue/green.

U need a harness from a 2500 from 99-02 model.

brandon6.0

iTrader: (32)

your PCM will need a segment swap done for the 80e conversion as well.

78Chevyc10

Any way I can keep my harness? No luck finding a harness this weekend and I don't want to spend the money on an aftermarket one?

bigdaddy350

Speartech offers a 4L80E add on harness. Think it's 250 bucks. I'm in the same boat with my swap. Donor truck was a 5 speed.

JoeNova

You only need the trans portion. You can pull it from a harness and pin it into your ECU fairly easily. Its a dozen wires or so.

You can also use a 4L60e transmission harness, you'll just have to buy an 8 dollar VSS connector and spend 10-15 minutes taking a couple of pins out of the trans connector and splicing them to the new VSS connector. It should be MUCH easier to find a 4L60e harness.

78Chevyc10

I'll look into it little expensive but sounds like the easiest route.

brandon6.0

iTrader: (32)

hmmm when u mean the harness wires were deleted, was this an original standard trans harness? or did someone originally cut the trans portion off? if it was cut just go to the salvage yard and cut the trans wiring and splice back in. or tie the trans portion into the pcm using lt1swap howto pinout. this is the cheapest way. harness shouldn't cost more than 50$ and a case of beer lol