700R4 Conversion FAQ

[Project1970]

I suppose it's about time someone wrote one. Feel free to contribute.

Which one to get?
The 700R4 was produced from 1982 until 1992. It was renamed the 4L60 for 1993, and I believe it's otherwise identical. 1994 brought the 4L60E, which requires a computer to run. The good years to get are any made in 1987 or later. Try to find a unit that has a mechanical speedometer as well, but if not, it's not a big deal to change one over. The 1987 and later units have quite a few improvements that do a lot for helping the 700's longevity.

If you're getting a rebuilt one, it's no different than any other kind of transmission - get it from a reputable shop. Ideally, the original core would be an '87 or later, but an older one with updated internals should work just as well.

Other Things Needed For Swap:
*Transmission cooler
*Cooler lines if there wasn't an auto in previously, or if the old ones are in bad shape
*TV (throttle valve) cable and a bracket to mount it - go to a dealer for these. P/N 25515598 Throttle valve cable @ $20.00 and Bracket P/N 22504927 @ $17.00 (GM) . Bracket has oppenings for accelerator cable and for the T.V. cable and bolts to back two bolts on Quadrajet.
*Speedometer cable - the one from my THM400 was just a few inches too short. Yours may work, but don't be surprised if it doesn't, the 700R4 is a long tranny.
*Automatic crossmember, shifter, and linkage if there wasn't an auto in previously
*New or modified driveshaft (chances are it will need to be cut and put a new yoke on it)
*Grade 8 hardware to bolt the crossmember in
*Metric bolts to attatch the torque converter to the flexplate - at least mine uses them, but given that the Chevy parts counter gave me SAE the first two times, my guess is not all 700's use them.
*Speedometer drive and driven gears, and possibly the sleeve, depending on the transmission and gearing/tire setup. There are two sleeves, depending on the size of the driven gear. Get the sleeve at a junkyard if you can; I didn't have the option of waiting and had to pay almost $60 for it over the GM parts counter!
*Patience

Tips for the swap:
For the most part, the 700R4 is a fairly straightforward install. There's nothing really special about the physical installation of the transmission; just drop the old one, put the new one in, bolt it all up, and drill holes for / bolt the crossmember in. Don't forget to mount the transmission cooler too! Call your driveshaft shop, measure the distance they want, and have yours modified to fit. (Now's a great time to go with a one-piece!)

The "tricky" parts, though, are the TV linkage and the TCC (torque converter clutch, aka lockup) wiring. I'm not even going to try to explain the TV linkage; this site does a GREAT job of explaining the details of it. It's also quite possible to "get it close" by just retracting the cable (it makes sense once you look at a cable, the end 'ratchets') and then moving the throttle hard to WOT (engine off, of course!), and then take it immediately to a transmission shop to have it adjusted. I set mine using the method in the page and it's working perfectly.

TCC wiring is much easier than it seems. The only problems occur mainly because GM used mutliple wiring setups inside. I'll describe my setup:
I want it to only have torque converter lockup in fourth gear. I also want it to disengage under braking, and under heavy throttle, so it doesn't kick down with the converter locked. So, first, I ran an ignition-hot 12V wire to a new brake switch for a later-model Chevy truck. You want a switch that has two sets of contacts - one that is connected when the brakes are off, and one that is connected when the brakes are applied. The latter will be connected to your brake lights, the former will be connected to the new 12V ignition-hot wire. From this switch, I ran a wire to the engine compartment, where I mounted an engine vacuum switch - simply, it's closed under high vacuum (low throttle), but opens up as vacuum drops (high throttle). This can be omitted if your engine doesn't make enough vacuum to keep it closed. From here, the wire goes down to the transmission's "A" pin on the connector. Inside the transmission, as far as the TCC goes, you have two things - a fourth-gear switch and the solenoid itself. Mine has a dual-wire solenoid and a single-wire, closed-with-pressure fourth gear switch. The 12V from the A-pin goes to one wire of the solenoid, and the other wire goes to the single-wire switch. When the transmission shifts to fourth gear, the switch completes the ground for the solenoid. If all other switches are closed (no brakes, low throttle) and all connections are good, the torque converter will then lock.

The variations here come from the fact that there were both one-wire and two-wire solenoids, one-wire and two-wire switches, and both closed-with-pressure and open-with-pressure switches. I'll start off by saying the open-with-pressure switches will only work with a relay; they're set up for computer-controlled cars. Make sure you have a closed-with-pressure 4th gear switch.
There are two other combinations other than mine that should work:
*A-pin to two wire switch to single wire solenoid
*A-pin to two wire switch to two wire solenoid to D-pin to ground.

If you're confused, and I don't blame you, think of it this way: You want 12V to the TCC solenoid when you want the converter locked, and to unlock it, remove the 12V. Use the switches / connections you have to do so. Also, if you have a single-wire solenoid, you can -only- control the 12V side.

Other notes:
Last thing I can think of is that I've read that sometimes a fresh 700R4 has difficulty hitting fourth gear; mine did. The solution sounds slightly scary, but it worked for me: jack the rear of the truck up, pull the wheels and drums, DON'T HIT THE BRAKES, make sure the truck is EXTREMELY secure, and wind it out to at least 100 on the speedo. Basically, an Italian tuneup, standing still. I make no warranties on that information, and it is rather dangerous in my opinion, but it does beat the alternative of winding it out to 100+ on the road.