Thread: 700R4 "Lock up" Torque converter

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when general motors designed 700r4 they wanted the trans to run at 280 degrees The part of the trans that makes most of the heat is the converter when it is locked up it make no heat gm put a orifice in the 4th gear curcuit to reduce the flow of oil to the cooler because they thought 98% of the time the converter would be locked-up in 4th. Thats what smokes these puppies when you tow in overdrive There is a solinoid that controls the tcc valve in the trans it needs power and ground to work if you supply 12 volts to the + side of the solinoid and ground the - side you have lock-up To get lock-up in 4th only you connect the neg side to the 4th gear switch But first you have to have a normaly open switch some come this way some do not test the switch in your trans to see which one you have gm sells them and any trans shop can get them.

Ok alittle late but it looks like the other guys have got it covered.
Hope everyone is not really confused now.
Tim

Gusaroo, Here is a site to compute your rpm.

Don Shillady
Retired Scientist/teen rodder

no link Don...

Gusaroo, There have been some changes in the Forum which I am trying to figure out, but here is another try at giving the link to a very useful site that can be used to calculate the engine rpm for given rear gear, trans gear and tire size.

http://home.tampabay.rr.com/1bking/c...calculator.htm

Don Shillady
Retired Scientist/teen rodder

Try Randy ring and pinion they have a calculator on there sight.
Tim

thx guys...

cook67,

What should I ask for from a GM dealer to get this switch? I am working on three different cars installing the 700R4 in them. In older days I recall using a vacuum operated switch to get power to the lockup on a 350C. I have one electric switch that I bought at a rod show from Kwik Wire that has a pressure switch much like an oil pressure sending unit with a tiny orifice in the end that screws into a 4th gear port on the side of the transmission. I tested the switch and it only takes about 8psi to close it. I have about 10 of the same wiring setups but only one pressure switch. Kwick Wire wants about $80 for the whole setup and won't sell the pressure switch by itself.

Ed

Ok I don't use the outside port looks messy and laterm 700s don't have them .Inside the pan there is a 4th gear switch in every 700r4 it is the one closest to the 1-2 accumulator rear of trans farest from where the wire harness enters trans. test the switch with a ohm meter to see if it is normally open or normally closed. You want one that is normally open. THe gm # is 8627332 Will no fit out side 4th gear port will fit valve body.One wire in the harness will go to + side of solinoid connect to 12 volts the - side wire goes to the 4th gear switch. since the solinoid only gets ground when the trans is in 4th gear you don't need a brake switch it unlocks as soon as the trans downshift into 3rd. You may also have a tcc solinoid that only has one wire that runs through different switchs to get power This set up come in carberated trucks You can remove most of the harness and just use the 2 wire 4th gear switch to supply power to the solinoid JUst make sure the switch is normally open I hope this makes sense to you I never buy switches they are in the trans all ready.