'86 700R4 lock-up

[86ltrain]

I'm a bit of a rookie when it comes to 700R4's...What controls the lock up convertor in my '86 K10? I just ordered a new tranny and they claim it has a one wire 12V lock up convertor. I know theres a 3 wire harness that plugs into the tranny, does this have anything to do with it?

[chevyhouse]

If you have a one wire hookup to the tranny that means you will only have lockup in overdrive. Wire this to a 12v source through a brake switch that closes when you hit the brakes or splice into the brake light wiring. I don't know what the 3rd wire would be for but the other wire is for a second/third gear lockup option, this is normally used for towing in 3rd as locking the converter greatly reduces heat. This requires interal wiring inside the tranny and a toggle switch to control lockup. The internal wiring is pretty easy but if you don't tow I wouldn't worry about it.
This link should tell you everything you need to know

http://www.bowtieoverdrives.com/cata...SUBCAT&CATID=O

[86ltrain]

Just got my new tranny today, looks identical to the original. It has the same three wire harness right by the shift rod, guess I'll treat it like the original...

[Rabid]

try here as well for some answers:
www.700r4.com

I had one in my 72. Beautiful deal once you get it dialed in. Kick a$$ gas mileage compared to the T350.

[Rabid]

ooops...chevyhouse already hooked you up with the link. My bad. good luck anyway.

[86k10]

Well speaking from experience since we have the same trucks, and I build these trannys quite regular, I do know that the A wire is hooked to the 4-3 switch, B is hooked to the 4th cl. switch and D is hooked to 3rd cl. switch. If you still have all original wiring, and who ever built it, put in all the switches yours has, you will have lockup in 2nd 3rd and 4th. But unless you pull the pan you will not know for sure. Most people think you only need lockup in 4th and to that I say You need at least 3rd and 4th, and if you work yours as hard as I do mine on occasion, yes you need even 2nd. And as I said if no one has butchered your original wiring you are already wired through the brake switch and when you put the transfer case in either lock position it should unlock it too. Good luck with your new one, if you have any questions by all means ask and i'll do my best to help you out. And if they built yours as good as the one I just put in my old 74 C 20 you'll be able to do this just like like me.

[made2drag]

I have a 86 700r4 that seems to have a bad 4th since it doesn't ever shift from 3rd to 4th. I think the last guy might have messed it up some how. I read that 4th can go after a rebuild or if someone doesn't have their TV cable right.

If I run the 700r4 in "D" instead of "OD", will it let me get by without having the lockup cable hooked up? I have heard that 85 and up will not burn up, if you run without lock up, but I wish I knew for sure. I like it how it is and it drives like a turbo 350, but I am wondering about excessive heat and wonder if that excessive heat is only when TC spins in 4th? My solenoid only clicked once and is probably bad, which is another reason im fine with no 4th.