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Installing the 700-R4
I recently replaced my Turbo 350 3-speed with a Turbo 700-R4 4-speed overdrive. This helps keep RPMs down on the highway, and saves a little gas too. The installation was surprisingly simple and trouble-free. The whole swap was done in one day in my garage.

I chose to run a non-lockup torque converter. I don't drive the car everyday, so I didn't feel this was really necessary. B&M and other transmission companies make wiring kits like part# 70244 to retain the lockup feature in car that doesn't have a stock computer (ECM). Check this link for
Summit Racing Equipment. Follow the links "Trans Rebuilds/Mods" and then "B&M Converter Lockup Controls."

The 700 is about 3 inches longer than a 350,
but the mount is in a similar location. However, the driveshaft needed to be shortened. It does use the same yoke, so this can be re-used if the stock driveshaft is shortened. In my case, I had a local driveshaft shop make a new shortened shaft, re-using only the stock transmission yoke. The shaft and universals are new. They told me how and where to measure to determine the appropriate length. In this case it was the distance from the rear seal on the trans to the centerline of the rear end universal.

Transmission Case length Distance from Bellhousing to mount holes
TH 350 27 3/4" 20 5/8"
700-R4 30 3/4" 22 1/2" or 27 3/4"*
TH 400 28" 27"
200-4R 27 7/8" 27"
*700-R4s that came from Caprices have two mounting bosses; one on the tail section, and one on the main trans case. I'm not sure, but I believe Camaro and Corvette transmissions have totally different mounting bosses.
As you can see from the above chart, the Turbo 400 and 200-4R have the same mounting distance. Therefore, you can use a stock "straight across" style 200-4R crossmember (which most SS Montes have) to use a Turbo 400. However, the 400 uses a much larger spline yoke, so driveshaft modifications are necessary.

The stock 350 crossmember had to be slightly modified, but overall, it was easier than I thought.
I had to cut about 1" from the front edge of the mounting perch on the crossmember (to clear the trans oil pan [see "D" below]). I also had to cut a new hole about an inch further back for the mount's stud. The same weird offset mount was re-used. These measurments are not 100% exact, but once your doing the job, you'll be able to see where to cut. Once again, I used a Sawzall for the cut and a 1/2" drill bit for the mount stud.

I discarded the original coolant lines and ran new #6AN stainless steel braided lines to a Perma-Cool transmission cooler mounted in front of the radiator. Be sure to wrap the lines in foam insulation or rubber hose to keep them from chaffing everything around them. Also be sure they are not too close to your headers or exhaust.

Thanks to Big John and Colin for helping me out with the installation, and John Lecuit from
G-Force Performance for some useful information about the crossmember.

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