Project Rust Bucket Overdrive Transmission Swap
First-generation Dodges (’89 to ’93) have a lot going for them. They’re cheap, they’re light, and they’re powered by the legendary 5.9L Cummins engine. In the case of our ’89 Dodge D250 project vehicle known as Rust Bucket, we’ve been pushing the performance envelope of this underutilized platform.
| Minimal, but important modifications are required to swap a hydraulically actuated 47RH four-speed transmission into a first-generation Dodge. The later-model electronically actuated 47RE four-speed transmissions will work as well, but all the electronics must be swapped over, or a manual valvebody will need to be installed.
Our last trip to the dyno (Oct ’10) netted us 514 hp to the wheels on nitrous, while still using a Bosch VE injection pump. When we looked at the power graph, however, we noticed a horrendous torque converter slip rate of nearly 20 percent, an unfortunate side effect of the VE pump’s heavy fueling at low engine speeds.
We finally decided the best way to proceed in the power department was to throw in the transmission towel and swap in a 47RH transmission found in ’94 to ’95 Dodge Ram diesels. This way we would have a lockup torque converter (which would eliminate our converter slippage), and with a 0.70:1 overdrive ratio and 3.07 rear axle gears, we expected excellent fuel economy, in addition to the power increase. Follow along as we take a quick look at all the parts and pieces that went into this swap, with dyno numbers to follow very soon.
