Project V8 RX-7: Part 5 – Choosing a Transmission, the Tremec T56 Magnum!
By Mike Kojima
When we were contemplating the buildup of our E-ROD powered RX-7, we planned to bolt up the same T56 six speed transmission that we had in the car when it was LS1 powered. This plan went to crap shortly before we decommissioned the 7 for the E-ROD swap when while driving under normal conditions–nothing abusive or even brisk for that matter–the transmission got itself jammed in 3rd gear and no amount of muscling could free it. Online forum research gave us the clues, but not until we pulled and disassembled the transmission did we reveal the culprit, a broken 3-4 gear syncro key.
We were dismayed to find that the syncro keys were flimsy stamped sheet steel. To fix the transmission we replaced the keys with billet steel parts and replaced the aluminum 3-4 shift fork with a beefy steel part and bronze shift pads.
|These stamped syncro keys in the T56 are flimsy and can easily break in normal driving causing the transmission to get jammed in gear. We replaced these parts with solid billet steel parts to fix our tranny.
Although this would fix the transmission’s immediate problems, we didn’t feel that the T56 was a good long term solution with our new more powerful LS3, considering that we might do some other things to it in the near future. The transmission also lacked that buttery smooth shifting we enjoyed back when the car was a rotary. We did a little research and decided for the money we should get the Tremec T56 Magnum.
|We replaced the aluminum shift forks with stiffer steel parts with bronze shift pads. Although these parts fixed our transmission, we still did not like its rough notchy shifting,
We could not convince Jeff to let us tear his brand new Magnum apart so we had to steal photos of the internals from 5.0 Mustangs and Super Fords since they did a bang up job of photographing the tranny’s guts.
|Welcome to our replacement transmission of choice, the Tremec T56 Magnum. This tranny is a beefed up T56 built to take 700 lb/ft of torque, 60% more than a old T56 with refinements to smooth and speed shifting.