Conversion - Fit and Clearance-Transmission

Denis St. Pierre and others who have installed 700R4 transmissions in their cars have posted extensive descriptions of how they modified their crossmember mounts to accept the longer transmission. That served as a starting point for our car, but Ron at Lone Star Chassis decided it would be just as easy and cost-effective to fabricate a new crossmember that bolted into the last two existing holes in the crossmember mount rather than cutting up the chassis pan around the tunnel. The new crossmember looks like it came from a Russian tank factory—it’s stout! It uses the stock Monza TH-350 transmission mount. The bigger 700R4 fits in the larger ’75 and later H-body tunnel just fine. The only problem I have is the larger speedometer pickup with Vehicle Speed Sensor adapter is too close to the tunnel to allow the stock speedometer cable to hook in because of the large radius bend, but a shorter cable allowed a tighter radius and mated with the pickup correctly. I am using a $65.00 kit from Howell Engine Developments to control the lock-up converter using engine vacuum and a 4^th gear pressure signal to tell the converter to lock up. I needed to find a way to adapt the 700R4 to use the ’76 Torque Arm with the three-link suspension. Denis St. Pierre recommends using the TH-350 short tail housing and cutting your output shaft with a cutting wheel about one inch from the end at the notch. My output shaft didn’t have a notch in it, and I really didn’t like the idea of cutting it that much to begin with. I found an ‘82-’92 Camaro/Firebird 700R4 tail housing with provisions for a torque arm for $10.00 at a local transmission shop. Although the bolt pattern for the H-body torque arm mount is different, you can rotate the mount clockwise 90 degrees and use the upper and lower bolt holes in the tail housing to mount to the first and third holes in the Vega mount. Since the torque arm and driveshaft have to be shortened about six inches anyway, you can also get a ’82-’92 Camaro/Firebird torque arm and mount, cut it, and weld the front part of the F-body torque arm and mount to the back half of your H-body torque arm to have the use of the correct bolt pattern for the tail shaft.

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