1987 R10: TH400 to 200-4R swap (mostly wiring??)

[RaysnCayne]

While the OG 305 TBI/TH400/3.08 10 bolt in my 87 R10 does okay buzzing down the highway between 71-74mph at 2800rpm, I'm just not enjoying that kind of a buzz for hours on end when I drive long distances. So I'd like to put in an OD trans. I have a decent, used 200-4R I'd like to put behind the 305. My main question is about wiring.
1. I have 100% factory harness that has one wire going down to the side of the 400 case. Can someone tell me what that wire's doing?
2. The 200-4R has a three-hole socket in its case. I'm wondering if I can simply get a different electrical connection with a single blade and just plug the factory wire into that? Or do I need to do some more wiring or hacking the harness for more inputs/signals to properly control the OD trans?
3. I have a 200-4R in my Biscayne that only has one wire to it to allow me to manually control lock-up in 4th. I simply flip a switch on the dash to lock it up or unlock it. So I'm fine doing this to control lock-up in 4th on my R10. But will that take care of all my electrical needs to make the transmission function properly overall in my truck? Or (as I mostly just stated in question 2) will I need some more wiring to make it all work properly?
Thanks

 

[NickTransmissions]

While the OG 305 TBI/TH400/3.08 10 bolt in my 87 R10 does okay buzzing down the highway between 71-74mph at 2800rpm, I'm just not enjoying that kind of a buzz for hours on end when I drive long distances. So I'd like to put in an OD trans. I have a decent, used 200-4R I'd like to put behind the 305. My main question is about wiring.
1. I have 100% factory harness that has one wire going down to the side of the 400 case. Can someone tell me what that wire's doing?
2. The 200-4R has a three-hole socket in its case. I'm wondering if I can simply get a different electrical connection with a single blade and just plug the factory wire into that? Or do I need to do some more wiring or hacking the harness for more inputs/signals to properly control the OD trans?
3. I have a 200-4R in my Biscayne that only has one wire to it to allow me to manually control lock-up in 4th. I simply flip a switch on the dash to lock it up or unlock it. So I'm fine doing this to control lock-up in 4th on my R10. But will that take care of all my electrical needs to make it function properly in my truck? Or (as I mostly just stated in question 2) will I need some more wiring to make it all work properly?
Thanks

The wiring going to your TH400 is for the detent solenoid. The 200-4R takes a lock up converter (converter with a clutch inside of it).

You will need to install a TCC internal/external lock up kit to ensure the converter clutch is applied in 4th gear. Painless Performance, B&M and TCI make them, as do other companies.

 

[RaysnCayne]

Thanks Nick.

So if I leave the wire to the detent solenoid unplugged (I'll just cap it and tie it off out of the way), that won't effect anything on the PCM side, will it? It won't throw a code or act up if it can't see what gear the 200 is in?

 

[Matt69olds]

Look up TCC wiring for a 700 swap. The TCC works and installs in basically the same way on a 200R4, the pressure switch is obviously in a different location on the valve body.

 

[RaysnCayne]

I'm familiar with wiring up the manual lock-up switch, Matt.
I just want to know if unplugging the factory solenoid detent wire (and leaving it unplugged) is going to cause issues with the truck's computer?

 

[Matt69olds]

The computer won’t care if the kickdown wire is disconnected.

Somewhere there is a switch on the carb or throttle that sends power to the kickdown solenoid. I think on some of the later trucks the computer sends a signal to a relay which disengaged the A/C compressor and energizes the kickdown solenoid, but either way the computer won’t care.

There are people here far more knowledgeable about these trucks than I am, I’m sure someone will have an answer.