I am putting a fairly strong carbed 350 into my 87 Formula and plan to use the 700R4 thats in the car for now (until it dies...but its fairly low miles and seems to be in great shape). What do I need to do to be sure the 700R4 works correctly? Mainly I am think about the lockup torque converter. The car has a carbed 305 in it now and most of the wiring is unplugged (I bought it that way), but like I said it seems to run and shift fine. What I would like to do is take just as much of that wireing out of it as possible to keep everything clean. My main concern at this point is the lockup torque converter though....and to be honest I am not even sure how that works. I am totally not concerened about emmisions on this car so if it can be defeated that would be fine...is it better to have it locked or unlocked all the time? Any suggestions would be apprecaited!!!

 

It is best to have it locked in steady cruise conditions above ~40-45 MPH.

How it works: There is a fluid circuit built into the valve body and front pump that provides fluid to the lock-up piston in 2nd-4th gears (no fluid flow in 1st gear). There is also a solenoid valve in the front pump through which this fluid flows back to the pan when the solenoid is de-energized, keeping the lock-up piston from being pressurized. The solenoid is powered by a circuit that gets switched 12v through the brake light switch, through the ECM harness, down to the connector above the transmission pan behind the gear selector shaft, to the solenoid for one side of the power circuit - the ground circuit goes from the solenoid through a 4-3 normally-closed pressure switch on the back of the valve body, back through the connector, back up in the ECM harness, back to the ECM. When the ECM wants to command lock-up, it completes the circuit to ground, energizing the solenoid, closing off the fluid path and pressurizing the lock-up piston. The 4-3 switch removes the ground path when the transmission shifts from 4th to 3rd to keep the downshift from being so harsh, then closes again.

Pretty simple, huh?

If you aren't letting the ECM do its job, there are a few different things you can do. First, you can check out the Tech Article linked from the thirdgen.org homepage, which gives a couple of options. There are also kits from outfits such as B&M which provide pressure and vacuum switches that give lock/unlock capabilty based on 4th gear and high (cruise) vacuum. You can also use the 4th gear pressure port on the valve body (not the same thing as the 4-3 pressure port switch). The "normal" function of that 4th gear port switch is to tell the ECM when the transmission is in 4th gear - some models use that information for different purposes, one of them being, in some cases, not commanding TCC lock-up until in 4th gear. But, you can use a single-pole, normally-open, closed-to-ground when pressurized switch to wire the function completely within the transmission pan to lock the TCC whenever in 4th (overdrive) gear. It's not a bad idea with that set-up to put a vacuum switch in the circuit to open the circuit when vacuum drops to give you more hill-climbing power.

Hope that helps.