I put a 93 tranny into my 86. The original transmission in the car only had 2 wires in it, with no 4th gear switch. My question is, is how does the computer know when the tranny is in 4th gear to engage the lockup?

The car side of the wiring has three wires, which makes me wonder if it is supposed to have more then just the power to the solenoid???

 

Yeah, here's how the wires go. One is an ignition hot lead, one's a ground, and the 3rd one gets the signal from the ECM for when to engage lockup. IIRC the 93 trannys actually have a 5 pin/wire plug. I don't know if you can just hook up the 3 that our cars use, or if you'd have to drop the pan and do some rewiring to make it work on an older setup.

 

So how would the ecm know when to lockup the converter when the ecm input wire went to nothing?

 

I found the answer to my own question. My 86 shop manual shows that the lockup on my lb9, auto setup is controlled completely by the ecm based on the temp, vss, and tps, etc..

 

I still don't know if that completely makes sense. The ecm wire is what actually makes the lockup solenoid engage and disengage. My trans guy was explaining how it works to me just today. He said the solenoid has power as soon as the ignition turns on, and the ecm wire grounds/ungrounds the solenoid, causing to kick on or off, so I don't know how it would lock up without the ecm grounding that wire. Then again, I seem to remember reading that there's a built in back up system that engages the lockup if those wires become disconnected from the trans, or maybe I'm just dreaming that I read that. But if I'm remembering what I think I read, the backup is hydraulically activated instead of electronically. 90 and older 700r4's have a valve in the valve body that does this. In my ATSG manual it says that they did away with that valve assembly sometime in 91, so the newer ones just have a dummy plug in the VB there. If that's true I guess if you lost the wires on a 91-up 700r4, bye-bye lockup!

 

I'll scan the page from the manual, apparently theres stuff programmed in the computer that energizes the solenoid on just the 305 TPI car at least

 

heres the page from the manual for reference...