1970 Chevy Chevelle -Transmission Mount Install

In the quest for lower e.t.'s at the dragstrip, we usually focus on installing horsepower-producing parts or traction-generating bolt-ons, but we pay little attention to making sure the hop-ups are securely held in place. If you've got a 500-horsepower engine held in place with a pair of worn-out and crusty O.E.M. motor mounts, you're going to run into big problems before too long.

The same goes for the transmission. Bolting in a state-of-the-art street/strip transmission with a big stall converter is a great idea, but it should go hand in hand with a new transmission mount. Besides, installing a new tranny mount is super-easy to do, and the cost is inexpensive.

For this Quick Tech feature, we installed a polyurethane mount (PN 3-1108) from Energy Suspension on our Cheap Street Chevelle. The polyurethane design is soft enough for use on the street, but rigid enough to handle harsh driving conditions like drag racing.

Although the two transmission mounts look fairly similar, they differ greatly. The Energy Suspension mount (right) is made of polyurethane and has a safety locking design to prevent mishaps during extreme driving conditions. Plus, the mount can be used on GM automatic (including TH400) and manual (including three-, four- and five-speed) transmissions. Our stock tranny mount was bent and covered in grime, and the rubber was severely cracked and starting to crumble.
Although the two transmission mounts look fairly similar, they differ greatly. The Energy
Begin the tranny mount swap by jacking up the vehicle to gain better access to the transmission. Be sure to use jackstands to support the vehicle's weight. Don't rely on the floor jack alone to hold the car.
Begin the tranny mount swap by jacking up the vehicle to gain better access to the transmi

Using a socket and ratchet combo, loosen the two bolts that attach the transmission crossmember to the O.E.M. rubber tranny mount.
Using a socket and ratchet combo, loosen the two bolts that attach the transmission crossm
To remove the O.E.M. mount from the automatic transmission, use a 5/8-inch wrench to loosen the two outer bolts that thread into the bottom of the transmission.
To remove the O.E.M. mount from the automatic transmission, use a 5/8-inch wrench to loose

Use a jack (we used a floor jack with a block of wood) to lift up the tailshaft of the transmission a few inches to relieve the weight on the O.E.M. transmission mount. With the tranny lifted up, remove the worn-out tranny mount. With the mount removed, carefully check the crossmember for cracks and/or signs of fatigue.
Use a jack (we used a floor jack with a block of wood) to lift up the tailshaft of the tra
Just as the old transmission mount came out, slip the new Energy Suspension mount into place. Be sure to have the special preload plate sandwiched between the transmission and the polyurethane mount. Do not discard the preload plate thinking that it's just a shim--it controls the amount of preload between the mount and the transmission.
Just as the old transmission mount came out, slip the new Energy Suspension mount into pla

Once the tranny mount is in place, lower the transmission back down onto the crossmember (with the tranny mount in-between). Tighten the original mount-to-transmission bolts (arrow) and then thread-in the two new 7/16-14x1-inch bolts. Torque the bolts (to 40-55 lb-ft with a steel tailshaft or 30 lb-ft with an aluminum tailshaft). That's it, you're done with the swap. It's that easy.
Once the tranny mount is in place, lower the transmission back down onto the crossmember (