The Stovebolt Site Forums The Shop Area Engine Shop 700r4 lockup controlers

I am going to put a 7004r in my 69 C10, I've built the transmission and engine and I'm trying to finish the rust repair before doing the fun mechanical work. I need a lockup controler and I was wondering what you guys were using and and if you are hakkp with them. I know I can run without one but if I'm going to all the trouble to put it in I may as well take full advantage. Thanks for your input.

Sean

The early ones had a vacuum-actuated switch, mounted on the firewall, and a governor pressure switch on the valve body, wired in series. It took a combination of moderate to high manifold vacuum and enough governor pressure(speed) to close both switches. Either stepping down on the gas, or losing speed would disengage the lockup clutch. Later ones used a signal from the powertrain computer. Governor pressure corresponded roughly to MPH, 45 PSI=45 MPH, etc. We used to change pressure switches to keep from dropping in and out of lockup because of speed limits, etc.
Jerry

Go to www.bowtieoverdrives.com for info on their pressure lockup kit.

I used the vacuum switch, brake switch & hooked up the valve body to lockup in 4th only. Love it. Brian

Like Brian, but I pitched the vacuum switch in favor of a toggle. Works great.
http://www.chuckthetruck.com/page26.html

I didn't do the toggle 'cause my wife might(but I doubt I let her) drive it, ya know. Brian

I did what I thought was a simple fix when putting the 700R4 behind the 350 in my 37. I pulled off the brake light switch and my nephew got me a small solenoid swicth that we put between the switch and tranny. So, when you touch the brake it energizes the solinoid which takes it out of overdrive. I have driven it a lot this past summer and it works real good. My.02.

I get the vacuum switch off late 80,s chevy vans. It is right on the outside of the firewall & has a blue & green wire connector which get also. If the trans. has pipe plugs on the side for 3 & 4 gear testing I put a 2 prong oil pressure switch in the 4th gear pressure outlet. Wire it all together with a hot wire when the switch is on. Put a vacuum hose from ported vacuum to the vacuum switch. Works great.It releases under heavy throttle & when you let up.

Thanks for all of the suggestions, I guess no one uses the controlers from TCI or B+M. This sounds much cheaper which is good. I'll look for the switch Saturday cuz I going to the wrecking yard anyway. Thanks.

Sean

The governor pressure switch is already there, but it's under the pan on the valve body. Just figure out which one of the electrical contacts on the case connector you need to hook up to.
Jerry

As Jerry says, I did all my wiring mods on the valve body & used only the 4th gear switch, then thru the brake light switch to the vacuum switch, this gives lockup in 4th only, & when the vacuum drops it kicks out, also kicks out w/braking. Glad to "see" you, HRL. Brian

Does the converter "cycle" with light throttle input. My wife's Boniville does this and it drives me nuts. From what I have read the B+M controler helps with this. Is it half throttle before it kicks out or just as you tip in. I can live with the half throttle deal. Oh and what kind of mileage are ya'll seeing?

Sean

That's the purpose of going to a higher pressure governor switch. The 4th. gear switch is supposed to be used for emission control purposes, not as a TCC engage switch. The original shift strategy would allow converter lockup in either 3rd. or 4th. gear, depending on throttle position and governor pressure. Using a higher-pressure governor switch keeps the converter out of lockup until the vehicle reaches normal cruise speed, and prevents that annoying in/out cycling due to throttle position changes.
Jerry

No Sean, no "trailer hitching" on mine, as it locks up only in 4th. The 4th gear switch must have a paint stripe on it IIRC to work as HRL descibes. Mine already had the "proper" swtich, it is hooked to the case connector, all other wiring inside the valve body was removed, except a ground, I think. Seems I got some wiring info from bowtieoverdrives or chuckthetruck's website. Brian

At a minimum, make sure you lock the TC clutch when in 4th. The the TH700R4 bypasses the trans cooler and dumps the fluid in the pan when in OD (4th). Prolonged 4th gear use can cook both trans and fluid.
If you examine GM's scheme for fourth gear TC lockup, they prefer to drop into 3rd and unlock the convertor when more load is encountered in OD situations.
Cheers,
MV

I found the vacuum switch today, it sounds like I need to pull the pan off my trans and find out which pressure switch it has. My trans was origanly in an 88 G20, from what I understsnd these had all of the durablity improvements. I guess it will give me a chance to install a drain plug while I'm there. Thanks for all the advice.

Sean

It,s easier to take the plug out of the 4th speed test port & put a 2 prong oil pressure switch used for choke heaters. They are cheap & you won,t have to drop the pan.

Droping the pan is no big deal it's not in the truck yet, but I'll keep that pressure switch idea in mind in case I need to change how it acts. Thanks for all the info and all the ideas, you guys have saved me some money.

Sean