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-   -   th 700r4 lock-up (http://www.hotrodders.com/forum/th-700r4-lock-up-136722.html)

jean-karim 04-09-2008 08:54 PM

th 700r4 lock-up
 
Hi All!

I have a carb 355 engine swap in my LG4 1985 Trans-am , no more ECM and still the TH 700 tranny , so I need to get back my lock-up working , so so far that's what I did : I tracked the original lock-up wiring coming out of my tranny what is exactely happening is when I wired the purple wire to 12V brake switch and wired blue together with tan/black it locked in all gear from 1 to 4...and even braking did not unlock...Then I've tried wiring still purple to that 12V ( by the way there are 2 brake switches at the pedal , one seems to have a vacuum? ) and tan/black to ground , blue to nothing and again locked in all gears ( did not try up to 4 ) then I've tried again purle to same 12V and blue to ground and tan/black to nothing and driving in city it did not lock in first 3 gears , did not try fats enouph so check 4 . So would that blue to ground and purple to 12v would be the way to lock in 4 only?
Thanks lot!!!!

scr8pin_f100 04-20-2008 09:27 AM

I'm gonna follow this thread closely..I too have a th700r4 in my beast and I was actually just planning on buying a adapter wiring kit to bypass the lack of a ecm..But if everyone here figues out how it is done cheaper, then that would be great...Needless to the wiring kit is kinda pricy!

1drwgn 04-20-2008 08:40 PM

check out monster trans on ebay, they have a kit that involves a pressure switch and only locks up in 4th gear, only downside is that it deasnt unlock on coast or braking, but trans will bump to lower gear and its almost not noticeable.
i have one on the caprice and its easy to put in.

jean-karim 04-22-2008 02:38 PM

but I already have the original wiring from the tranny, so I'm looking to just hook properly those 3 wires in order to activate that lock up ;) , I read all people telling to buy an after market wiring but as far as I still have the original wiring i don't see why I would change it... :confused:

1drwgn 04-22-2008 04:15 PM

just get an oil pressure switch, a normally open that closes with pressure, it needs an 1/8 inch npt i believe. wire it into 12v source and install switch on passenger side pressure port right behind servo this is 4th gear apply pressure, so when trans goes into 4th it will lock up. if you want you can even add another switch to open converter when u step on brakes or a throttle switch to open when you let off gas, but its not necessary and a lot of work.

Big Don 04-22-2008 08:47 PM

400r od switch
 
Okay< I know this is a cheap way out, but here is what I did with a set-up I was running a while back.

Same story, 455 olds with carb and 400r trans. Of course it would not lock up without the proper ECM.

So I wired the lock up wire #### No laughing now#### To an old floor mount dimmer switch with a pilot light to tell me when it was not in lock up.

It was lotsa fun when cruzin at around 50 mph and some guy in his Jap Crap tried to fly by me.... With a little practice you could stomp the 4bbl open at the same instant that your left foot stomped on the switch to drop it out of OD. The flippin thing would just leap and accelerate like a rocket, leaving the Jap Crap driver looking stupid and confused as he watched that old turtle top pull away. I really enjoyed burning off Mitubitsi 3000 GT's..... Heee Heee!

Cousin_Joe 06-04-2008 08:48 PM

:confused: Anyone ever figure out what color wire is postive and which is ground?

SSedan64 06-05-2008 12:50 AM

Lockup Wiring = 12V to pin A on plug. Look at all these links and they should answer all TV hookup questions & lockup questions.
http://www.chevyasylum.com/tech/4thgear.html
http://www.hotrodders.com/forum/atta...chmentid=11826
http://purplesagetradingpost.com/sum...o/700R4p1.html
http://www.tciauto.com/Products/Inst...76600_inst.htm

Cousin_Joe 06-05-2008 06:53 AM

Which pin is the A pin? I follow the 12V to A thing. As simple as possible, is it upper left? Lower left? I'm having trouble diagnosing my problem because everything I read says pin A, pin B, pin D. I have NO idea about what pin is what, I just have the stock connector on there. Thanks!

jean-karim 06-05-2008 07:07 AM

OK , THEN FOR THE FIRTS TIME IN CAR HISTORY i'M GONNA MAKE THIS SUBJECT SIMPLE!!!!!!!!!!!!! :thumbup: no kidding never found even once a simple explanation!!!

On my car 85 transam with the TH700R4 I have the original wiring that's coming out of the tranny for the lock -up , it's a 3 wires . On my car I had color purple , blue and brown/black . A is the 12V , B and D the two others . So I hooked the purple to 12V key source, and blue and brown/black hooked together and both to ground.
Now depending on your tranny you could have different switches . mine was locking then an all gears wich was anoying so I grabed a fog-light switch and hooked those wires on so I could lock manualy on overdrive only. And now my lock-up works perfectly. ;)

SSedan64 06-05-2008 06:44 PM

Quote:

Originally Posted by Cousin_Joe
Which pin is the A pin? I follow the 12V to A thing. As simple as possible, is it upper left? Lower left? I'm having trouble diagnosing my problem because everything I read says pin A, pin B, pin D. I have NO idea about what pin is what, I just have the stock connector on there. Thanks!

Ok, Plug should be marked with very small letters A=top left, B=top right, C=bottom right, D=bottom left.
A=12Volts feed from brake or toggle switch,........................................... ........
B=4th gear switch ground to ECM- Computer Cars, ..................................
C=3rd gear switch ground to ECM- Computer Cars, ...................................
D=Computer feed ground to activate Lockup............................................
A=Purple usually........................................... ......................................
B=Light Blue usually........................................... .................................
C=Dk Green/White usually........................................... .........................
D=Tan/Black usually........................................... ................................
Some Trans have 1, 2, 3 or 4 wires depends on model, computerzied or no Com.


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