700r4

[Francis Blake]

Bought a 700r4 trans today, it came out of a running car so hoping it will be good. My friend with the h.r. shop gets them from a dismantler he knows for core price ($50.00). I have to get a torque converter and flex plate for it and don't know if all years for it are the same. Do all the 700r4 trans use a locking converter? It is a k model, supposed to be a heavy duty model.

 

[Keeper]

What year is the transmission? The later years are better then the older. Not all use the lockup, and you do not technically need to install one.

If you are looking for info, head over the bowtie overdrive and plan on spending a couple hours reading.

 

[Zandoz]

Just a heads up on something you may or may not know....the 700R4s were built with two bell housing designs. One for the 60V6s and one for the SBCs and such. Before you invest time and money on yours it pays to be sure which you have/need. A friend made that very expensive oversight.

 

[RPM]

I don't think you need any special flex plate. On your converter, if you are going to lock it up, look at a converter for the 4cyl S-10. They stall at about 2500 rpm but lock when in OD.

 

[choppedtop]

When your ready for your first drive, make double sure the tv cable is adjusted correctly. They can kill a 700r4 in less time than it takes to remove and install. I have been told that the mid generation is the best. Dunno about that for sure. I do have the mid in my rod, and sure do like it. Not running a lockup in mine.
Lee

 

[Francis Blake]

Thanks for the information guys. Ron that 4cyl converter would be the best of both sides of that issue. For sure the tv cable has to be right, my son ruined the trans in his truck because he wouldn't leave it alone. I will get professional help when I get to that point.

 

[Hotrod46]

89 and later are considered the best. The 700 was modified several times over it's life and these models had the latest parts.

Also, it's not just a matter of adjusting the throttle valve (TV) cable properly. The angle of the cable mounting stud on the carb is also critical. The cable needs to be pulled out in the right relationship to the amount of throttle opening. Here is a site that I found helpful.

http://purplesagetradingpost.com/sumner/techinfo/700R4p1.html

As far as the lockup not being needed, the 700 in my bucket has a temp gauge in the pan. I have the trans set to lockup in 4th (OD) with a toggle switch to disable the lockup if I want to. I can tell you that the trans temp runs about 20 - 30 degrees hotter with the convertor unlocked. The cruise RPM in OD is low enough that the convertor slips and generates more heat. Run it locked and the pan temp never gets over 160 on the highway. I'm running 29" rear tires and 3.42 gears. I cruise at 2000 RPM's at 70.

Lockup is easy to wire and most 700's already have the switches on the valve body to do it. There is an electric solenoid valve on the valve body that needs 12 volts when you want lock up. Put a normally open pressure switch on the 4th gear pressure tap on the valve body and send 12 volts to the circuit. When the trans shifts into OD, the pressure switch closes, energizes the solenoid and you have lockup. Most 700's have several switches on the valve body. You just need to make sure the one you use is open with no pressure on the switch (normally open - NO). Get the pigtail off of the trans wiring harness in a car or truck that had a 700 to send power to the trans.

You also need a way to cut the power to the lockup when you hit the brakes. I used a common 5 pin automotive relay. The brake light switch energizes the relay coil. The normally open relay contact is wired to the brake lights and the normally closed contact goes to the trans lockup. The brake light fuse protects both circuits that way.

Good luck.

Mike

 

[Francis Blake]

I just finished researching this trans and found it to be a 1990 heavy duty model. That is good info on the tv cable. the hr shop I bought this from has done a boatload of these using a brake light switch and he is going to help me set up everything when I get it installed. All I need now is some nice weather so I can get to work on it.

 

[Keeper]

Very cool, if you can take some pics, I would be interested to see the brake light switch setup.

 

[Francis Blake]

I will do that just as soon as I can to work on it.

 

[RPM]

Very cool, if you can take some pics, I would be interested to see the brake light switch setup.

This works very simple. You use a brake light switch for a mid 70s GM with cruise. It has 4 terminals on it. Two for your normal stop lights and two for the cruise. The two for the cruise are used for the lock up, along with a toggle on the dash. You run a hot wire through the toggle, to the two terminals for the cruise, then to the lock up terminal in the tranny. So with the toggle in the on position when the trans goes into OD the converter would lock up. Apply the brakes and the cruise switch opens the circuit and unlocks the converter. In you are going fast enough to stay in OD when you release the brakes the converter locks again. If the trans dropped a gear or two while the brakes were on the converter is unlocked till it sees OD again. It has to run through the stop switch or if you got in a hard panic type stop with the converter just locked from the toggle it could possibly stall the engine. Not a good situation at highway speeds.

 

[Francis Blake]

Ron there is a guy that shows up at a cruise might at one of the local drive ins that had his fixed that way and he would forget to unlock hie converter and kill his engine in traffic. Not a good situation.

 

[Keeper]

Thanks Ron, that is an interesting setup.

I am currently using the vacuum lockup kit and I have issues with it hunting at city speeds, drives me nuts. I usually end up driving around in 3rd around the city. Sort of defeats the purpose of the OD.

 

[RPM]

Thanks Ron, that is an interesting setup.

I am currently using the vacuum lockup kit and I have issues with it hunting at city speeds, drives me nuts. I usually end up driving around in 3rd around the city. Sort of defeats the purpose of the OD.

Most cars with lock up converters will do this. My Chevy truck and my wifes Chevy Suv will do this right at 45 mph. the speed where the converter would normally lock up. With the toggle on the dash you can just turn the converter off, and eliminate this.

 

[Hotrod46]

+1 on what Ron said. The vacuum switches are not needed.

I tried using stock GM vacuum switches on a couple of setups I wired. Pirated the switches off of early 80's GM trucks. Stuttered in and out of lockup all the time. I finally just eliminated the switches and the setups worked great.

 

[bobs66440]

Most cars with lock up converters will do this. My Chevy truck and my wifes Chevy Suv will do this right at 45 mph. the speed where the converter would normally lock up. .

My S-10 Blazer would do that also. Very annoying...

 

[Indycars]

Nobody said whether they are using an adjustable vacuum switch. I've setup mine with the TCI adjustable vacuum switch that can be bought for $29 at Summit and 2 post pressure switch # 65618A in the valve body to detect 4th gear. I've yet to drive it, so I can't say how well this is going to work.



http://www.designflexswitches.com/switches/psf101.php
http://www.summitracing.com/parts/tci-cmp3766b/overview/


This is how I wired mine.




There are several adjustable switches and you might find one in the salvage yard, on one of these cars.
GM #14014519
BUICK 87-81
CHEVROLET 87-79
GM LIGHT TRUCKS 87-80
OLDSMOBILE 87-81
PONTIAC 87-80




http://www.superior-transmission.com/Product_Page.cfm?ID=186



Now this guy has gone to great lengths to understand and improve how the lockup works with a 700-R4 transmission. Lots of wiring diagrams included in this website.

http://www.rowand.net/Shop/Tech/LockupTCCWiring.htm

 

[Hotrod46]

The adjustable switch looks like a good idea. The stock switches I tried didn't have much space between the unlock point and the reset point. Small changes in throttle opening caused the vacuum to fluctuate enough to make the switch open and close.

I really don't think on a powerful car they're needed, though. It made sense on the underpowered cars of the 70's and 80's to unlock the convertor on hills and during light acceleration. Those pitifully weak cars and trucks needed all the help they could get! On the average hot rod, you'll never notice the convertor doesn't unlock.

The only possible risk I see is damaging the fairly small lockup disc in the convertor with too much power. Since my car only locks in OD, I just drop down to 3rd when I want to get on it hard. I also have a toggle switch to drop out the lockup manually. My cam doesn't like the locked convertor in town. I could probably use a little more rear gear.

 

[Indycars]

I like the idea of the manual switch wired like it is in my drawing. It would allow you to lock up the torque converter in the lower gears if you were creeping along in traffic or maybe if you were in a parade. I noted this only works in 2nd, 3rd or 4th gear on the drawing. Not sure where I got that info now, when I look at the drawing now, looks like it should work in 1st also. Guess I will figure it out after I get the car running again.

 

[Hotrod46]

The valve body is set up internally so that the trans can't lock up in first gear. Only 2nd, 3rd and 4th.

I should also mention that I have heard of an internal mod that can be done to certain 700's that will lock the convertor in 4th without the need for the solenoid. All done hydraulically from inside the valve body. Every time the trans shifts into 4th it locks. My trans guy talked about it, but I wasn't sure I would like it. I have no idea what is done to achieve this.