700R4 Lockup Torque converter control issues solved

[idahovette]

Can you lock up a 2500 stall converter in a 700R4?

 

[SirRobyn0]

Ok so this did answer a few questions, like what that deelybobber is on firewall...and that with new $900 harness that has bubkiss for it.....ill never waste money on a named wire harness again......absolute waste of money.....sorry i should not get started on that topic. Anyways ill give you a breakdown of my setup....ill try to make it short. Ok its an 1981 body, single cab longbed 4wd k10 w/ 3/4 running gear from 1984 k20. Originally a 305 w/esc and i assume a th350 (3spd.) Now has blueprint 383, w/ built 700r4, 89 column (4spd) those are important details that i never know til its to late. So here is where im stumped, oh and its a 2500 stall. So the trans man, added a lockup in trans for the 4 pin plug, it has a +, -, or ground i believe ( ill snap pics and add later) i bought a 4 pin pigtail, but think it only had 3 wires.....so my first question is if not wanting to be responsible for flipping a switch ( i may forget its on or ? ) what would i wire the wires from 4 pin pigtail to ? And let confuse you and back up a bit, so the original setup (81, 305, th350) had a vacuum deelybobber like yours and also had a brake and clutch pressure pin near brake pedal, but somehow was also wired into a small box up on left side back of steering column frame called by pt.# tcc lockup relay, with doubled wire colors that i can only assume by what wires i could find of original harness go to brake, clutch switches and splice into transfer case wiring and possibly cruise control. Thats when i started getting confused and the dumb/expensive harness does not provision nor give any instructions, and the actual wiring diagrams all 20 something of same components all are confusing or do not detail any tcc relay or where it would be wired to.......... so with all this ive written, im sure ive only confused you more then you wanted....lol. any feedback would be appreciated and will give more precise information and pics next time i get a chance....thank you my friend.....sending pics of what i may have on phone, but probably not what you need for reference

Ok I'll do my best here. In the original setup it would have had to have had the TH350C The C indicated it had a lock up converter. A normal TH350 did not have a locking converter.

So one issue you have with the new transmission is we have no idea what solenoids are in the tranny or if they are hooked up inside. For the moment lets assume they are all there and hooked up.

My 700R4 is currently setup so it engages the converter clutch automatically in 4th, and manually with a switch in 3rd. I did this because I wanted control over it when towing, in 3rd. From the factory some 700R4's would only lock up in 4th, some in 3rd and 4th, some used the vacuum control in 3rd, and were always locked in 4th, others used the vacuum controller in 3rd and 4th. No matter the configuration they were wired to disengage when the brake pedal is pushed.

So first thing you need to decide is if you want it to lock in 3rd and 4th or 4th only. The simplest wiring would be always locked in 4th only. You could always start with that and then wire in a lock method for 3rd later. IDK you'll need to decide that. If it's currently got a manual lock up switch you could retain that to run the lock up in 3rd if desired.

Then after that I'll have to see if I can find my wiring diagram for it.

 

[SirRobyn0]

Can you lock up a 2500 stall converter in a 700R4?

Well that's a really good question. I have no idea, in thinking about it maybe not? That's a question for one of the tranny guys to answer. and @ak4life we need to get an answer to that question before you proceed.

 

[Matt69olds]

Well that's a really good question. I have no idea, in thinking about it maybe not? That's a question for one of the tranny guys to answer. and @ak4life we need to get an answer to that question before you proceed.

You can get converters with lock up capabilities far beyond 2500rpm, just depends on the budget. The problem with high stall converters is as stall speed goes up, converter diameter usually goes down. As a result, the lockup clutch gets smaller, and torque capacity goes down. You can get small diameter converters with multiple clutch disc to get the capacity back up, but that means more fabrication, more labor, more expense.