True Connections

This month we will discuss automatic transmission swaps. The most common swap is taking out a 2 speed powerglide and installing a more economical 3 speed, such as a turbo 350 or 400. To remove the power glide, you must first begin by raising the vehicle off the ground. It is usually a good idea to drain the trans of fluid before removal so it doesn’t get all over your garage floor. While it is draining, you can begin removing the shifter linkage, kick down linkage, and the vacuum modulator line. Once the trans empty of fluid, remove the transmission cooler lines with a flare wrench. Be sure to have your drain pan close by since the cooler lines will still have fluid in them. The next step is to remove the drive shaft by unbolting the u-joint from the yoke on the rear end, sliding the drive shaft forward to clear the yoke, and then sliding it back to remove it from the transmission. Next remove the dust cover in order to reach the three bolts connecting the flexplate to the torque converter. You will need two 9/16” open end wrenches to unbolt the converter, and a flywheel wrench to turn the motor over so you can reach the bolts on the other side of the converter. Once the bolts are removed, slide the converter back towards the trans and make sure it stays with the trans during the removal process. Now we are ready for final separation of engine and trans. Support the transmission with a floor jack fitted with a transmission cradle, and support the engine from up above with a cherry picker. Unbolt the transmission mount from the crossmember and raise the transmission slightly so you can unbolt the crossmember from the frame and slide it out of the way. Now you can lower the trans just enough to reach the 6 bellhousing bolts. Use caution at this point since once the bellhousing bolts are removed the transmission will be free of the car. To install your new 3 speed automatic, simply follow the reverse of the above procedure. The turbo 350 transmission will drop right in, you can even use your existing driveshaft and yoke.

The only differences will be in your shifter linkage and the kickdown linkage. For the kickdown, the turbo 350 will use a cable that runs to a stud on your carburetor, so the old powerglide linkage can be thrown out. If you have a column shift car, there is an aftermarket bracket available that bolts to the side of the transmission and accepts your stock powerglide shift linkage. If you have a floor shift car, you will have to take out the stock linkage and install a cable. To ease this process there are two kits available. One kit supplies all the brackets and hardware to mount the cable to the transmission and the other kit will mount the cable to the shifter, and includes the new detent hardware. All of these items make the changeover very easy, so next time you think about pulling out your old powerglide, just go for it. In the upcoming articles we will be continuing our discussion of transmission swaps including Turbo 400, Turbo 700R4, and 4 speed manual conversions.