"Buick Trademark(s) used with the written permission of General Motors"
Home Forums Garage Classifieds Reference

Technical Reference #11

700R4 conversion

Authored by Wes Vann, last modified on August 14, 1997

PLEASE NOTE; Always use jack stands while working under a car. I would also recommend that you have another person present when lifting a transmission into place.

This page is written with a 64 Chevelle as an example. Unlike most of the other pages that I've written for this section, this isn't a project that I have personally done. The data stated is as accurate as I can get, however, should you find something that appears wrong, please contact me.

It's going to be written as a list of items that you have to be aware of in order to do this swap. This should be typical of all GM models. The items are going to be written in real general terms and not as a step by step procedure.

ITEM #1:

The 700R4 is larger in width than even the TH350. This means that you will have to massage the floor pan on the passenger side of the tunnel (adjacent to the firewall). This is as told to me by a person that installed one in a 64. Other models may not require as much hammering, but, I'd assume that some is required. You will not know until you trial fit the trans. The idea of having to trial fitting a trans isn't fun, but count on having to do it!

ITEM #2:

The driveshaft will have to be shortened. The amount will vary and it's best if once the trans is installed, you follow the instructions of your driveshaft shop in order to measure for the correct length. It may seem like a cop-out that I don't just say that it's 3 inches, but cars vary!

ITEM #3:

You will have to add some electrical circuit to control the torque converter lock-up. I talked to the people at B&M (hey, I live in L.A.) and they told me about their kit to do this function. How it works is that there is an electrical sending unit that goes on the trans, where the speedo cable is hooked up, that monitors vehicle speed (the speedo cable then hooks up to it). There is also a wire that gets spliced into the brake light switch. Then a little panel gets mounted under your dash that has a control switch where you can set the desired speed where the lock-up occurs (between 30 and 90 MPH). There is an led that indicates when the trans is "locked up". You also have to provide a ground and 12 volt source.

ITEM #4:

You will have to have some kind of trans cooler. This shouldn't be any problem if the car originally had an automatic. What can be a problem is reaching the fittings once the trans is in place. A solution to this problem is to have a short section of hard line installed prior to putting the trans in place.

ITEM #5:

Should you desire to run with a non-lock-up torque converter, there are several easy changes that have to be made inside the trans. Per the people at B&M, it's about as easy as doing a shift kit in a TH350. If you don't make the changes, the trans will tend to run hot.

ITEM #6:

It's my understanding that the stock rear trans crossmember can be used by just sliding it rearward and drilling some new holes in the frame.

ITEM #7:

A 700R4 has what is called a "TV" cable (and not what is called a kick-down cable as in a TH350). It hooks up similar to a kick-down cable and most of the brackets are the same. What it does is give the transmission the throttle position so that it knows when to kick-down. It's adjustable and depending on the cable and brackets you use, the method varies.

ITEM #8:

Things to look for when getting your trans (thanks go out to Don Seributra for this information);

A: Look for a 1987 to 93 core. These should have a #732 as the last three digits on the front pump. These trans have a 10 vane pump, 30 spline input shaft, an auxiliary valve body, and a 28 element inner sprag race.

B: Avoid the older transmissions unless you plan to retrofit with the 87-present internal hard parts.

C: Avoid the "E" models due to the fact that they are computer controlled (unless you are going the full computer EFI conversion).

Good luck and be careful (a transmission falling off the jack onto your hand isn't a pretty site!)