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Discussion Starter #1 (Edited)
OEM 4L80E TCM Questions

I have a 1993 GMC 3500 Van powered by a 6.2L and backed by a 4L80E.
I bought this van as a donor for one of my FSJ projects.
So far, I have not decided whether to use the 6.2 or a 12V Cummins core that I have stored.
Anyways, I know I will be using this 4L80E.
Lucky for me, the 6.2 is an all mechanical engine, so the 4L80E needs a standalone TCM to control it.
This is a MUCH cheaper solution than some of $1000 aftermarket TCM that a person can purchase.



However, the pitfall for me is the wiring.
This harness runs from the TCM into the main harness in the engine bay.
Out of this main harness, some wires trickle back down to the 4L80E.
In planning for this swap, this TCM wiring has me intimidated.

Has anyone here used a OEM GM 4L80E TCM in a swap?
Was the wiring as bad as it looks?
If you have performed this swap...could you provide any tips, tricks or secret handshakes?

Does anyone like Painless, produce an aftermarket wiring harness?

Any and all suggestions, recommendations or flames are welcome!
 

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this has been discussed here before, do a search you will find some good info.
 

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Discussion Starter #4
this has been discussed here before, do a search you will find some good info.
I did perform a search.
What I discovered was the discussion and part numbers for using the OEM TCM, but not any deatails about the wiring harness.
If I have overlooked something, help me and provide some links.
 

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Discussion Starter #5

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more info http://coloradok5.com/forums/showthread.php?t=133632&highlight=4l80e

I have started thinking about this myself. I need a new trans and have been thinking about trying this just for fun. I have found a computer locally for $100. I would imagine the whole setup could be had for fairly cheap.

Pigsmith, have you considered getting a wiring diagram from any gm dealer? The local ones here are hapy to print them off for me, if I will see if I can get one later if I remember it.
 

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I have started thinking about this myself. I need a new trans and have been thinking about trying this just for fun. I have found a computer locally for $100. I would imagine the whole setup could be had for fairly cheap.
Agree 110%
A person can find a stand alone TCM for pennies compared to the $1000+ aftermarket units that most folks seem to have some complaint about.

While this wiring harness has be rattled, all the other pieces of this puzzle does not seem to bad.

Pigsmith, have you considered getting a wiring diagram from any gm dealer? The local ones here are hapy to print them off for me, if I will see if I can get one later if I remember it.
No, I have not.
sdstriper posted some links above from the Pirate4x4 forum that had some good diagrams.
 

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I have been looking into it more and it seems that you would have to hav a 91-93computer to use a 91-93 trans and will need a 94-95 van computer to use a 94 and newer trans. I still havent found anywhere that gives an actual breakdown on how to do this setup.

This is all off the net so dont take my word for it.
 

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I have been looking into it more and it seems that you would have to hav a 91-93computer to use a 91-93 trans and will need a 94-95 van computer to use a 94 and newer trans. I still havent found anywhere that gives an actual breakdown on how to do this setup.

This is all off the net so dont take my word for it.
I believe this correct.

I bought my '93 Van for $440 with a bad 4L80E.
I was able to pickup from a private GM only salvage yard a late model 4L80E that was a GM Goodwrench Reman unit.
(I was told these GM Goodwrench Reman unit are assembled in Ohio, in the Dayton area and are put together with tighter tolerances than a factory unit, thus a better tranny in the end)
I had a local Transmission shop install a Diesel torque converter and then install in in my van.
When started out to be a simple swap turned into a nightmare for the shop.
Come to find out, the wiring was incompatible from my '93 TCM to the later model 4L80E (late 90's model I was told)
An old school tranny tech at this shop rewired my van's wiring harness to work with the later tranny.
It was explained to me that the TCM is not really different, it just the pinouts on the connectors are.

I've been driving my van daily and it runs great and the 4L80E shifts fine!
 

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Bryan, I have heard the same info on the net (the wiring part).Now that you have it all working with your 93 tcm you should be able to purchase a helm wiring diagram for your 93 van (I think its about $20-$30 for obd1 diagrams) and it should be easy to seperate the wires and sensors from there.
 

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Bryan, I have heard the same info on the net (the wiring part).Now that you have it all working with your 93 tcm you should be able to purchase a helm wiring diagram for your 93 van (I think its about $20-$30 for obd1 diagrams) and it should be easy to seperate the wires and sensors from there.
I'll need to check into that!
Thanx!
 

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No problem. Could you please report back what you find?
 

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Some of the problem stories that are out there are early wiring harness specific. That is why you see update and conversion harnesses available. Internal and external wiring harness upgrades... Leaking transmissions and faulty wiring due to poor wiring connectors etc internal/external connections.
 
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