So i have the transmission installed and bolted up. My question is what to do about the wiring ? not the selector wiring, but the abcd plug on the front of the tranny.. my original th125 had 2 wires coming out of the 4 plug, and now I have 4 wires coming from it and not too sure how it all comes together..

is A D the TTC Brake? I have read about putting in a 54 psi switch in for the tcc brake for overdrive but how exactly does that wire in? this is in a 1987 GT FB 2.8... the plug is the square plug style if that matters.

thanks for any input.

Check out the bottom of this page. Have another somewhere but have not found it.

http://spacecoastfieros.com/tech/440-4T60/

I don't really follow his wiring diagram... his symbols are confusing as he shows the relay but only 2 wires of it and then the dotted line to the other connector... I don't see a pressure switch from the transmission in there as well. Hmmm. still confused..

I put a box around the relay. He used a normally closed contact of the relay (closed when relay is NOT powered)
The pressure switches open when the transmission shifts into the 3 or 4th gear which de-energizes the relay and closes it's contact. Once the relay contact closes then the ecm can power the TCC as needed. I believe the 3d gear switch is also open when the 4th is so he just used the 3d only and let the ecm do the work.


The dashed line is how you show which contacts are part of a relay...If you read, he did this because the ecm seemed to fire the TCC when coming to a stop once in a while so this takes away the ecm control of the tcc in all gears below 3d.

[This message has been edited by Dodgerunner (edited 03-01-2010).]

I think I cover that in my 4t60 swap thread:

https://www.fiero.nl/forum/Forum2/HTML/091777.html

If you still have the 4T60 out, I find it easier to just rewire the TCC control on the 4T60 to match that of the 125C (it was the same in some 85/86 models, but different after that). To do this you install the N.O 3rd gear pressure switch from the 125C and make sure the +12 input goes to the switch, then from the switch to the TCC, then from the TCC to ground.

Just use the diagram in the lower left in this pic:

Thank you Dodgerunner for fixing my blond moment. can't wait to get it all fixed up in the morning.

I found another diagram that uses just a pressure switch. When the switch is energized, it closes the circuit. No relay needed.

send me that circuit please. I have the relay one installed but would like to see the other style as well.

Link to thread w/ simple wiring: https://www.fiero.nl/forum/A...090219-2-087546.html

Picture posted in that thread:



Link to a thread I did a while back with lots of random info on the swap, including the above link: https://www.fiero.nl/forum/Forum2/HTML/098633.html

[This message has been edited by Alibi (edited 03-02-2010).]

So I go to the local Trans-drive transmission shop and ask for one of those pressure switches and they look at me like I just got off the short bus. then I try the auto parts store and they havent a clue what the heck i'm asking for. I went to the link that Alibi had for the switch and it says out of stock and has no option to reorder one.. .where can one get this elusive pressure switch?


http://www.transmissionpart...ctCode=480-000048388

About 2/3's down this page you can find several pressure switches at different rated pressures.
http://www.transmissioncent.../SwapInformation.htm

quote Originally posted by fieroguru: If you still have the 4T60 out, I find it easier to just rewire the TCC control on the 4T60 to match that of the 125C (it was the same in some 85/86 models, but different after that). To do this you install the N.O 3rd gear pressure switch from the 125C and make sure the +12 input goes to the switch, then from the switch to the TCC, then from the TCC to ground.

Bumping an old thread. You are talking removing the stock 4T60 3rd gear switch and installing the TH125c 3rd gear switch inside the trans? And by rewiring the 4T60 to match the TH125c you are saying to cut and splice the internal 4T60 wiring?

quote Originally posted by Hudini: Bumping an old thread. You are talking removing the stock 4T60 3rd gear switch and installing the TH125c 3rd gear switch inside the trans? And by rewiring the 4T60 to match the TH125c you are saying to cut and splice the internal 4T60 wiring?

Yes on both accounts... Take the side cover off the transmission, install the TH125c 3rd gear pressure switch and wire it up like the 125C. Some of the 85 and 86 4T60's came this way from the factory (I have one and the oem wiring schematic is posted above in this thread) and there is no reason you could not just rewire the TTC circuit within the tranny to this older style setup.

Very nice. For those of us not savvy in wiring this helps allot.