On a recent trip to L.A. Performance Division, our bone-stock '97 Dodge Ram put down 159 rear-wheel horsepower and 327 lb-ft of torque. Not bad, but not all that impressive either, and the 19-second quarter-mile time (at 69 mph) made us feel more like turtles than drag racers. We needed more go, but the OEM torque converter would only hold about 50 hp over stock, so we decided to step up and install a performance transmission and billet torque converter from BD Diesel Performance.
While diesel engines can go hundreds of thousands of miles, early diesel automatic transmissions weren't up to the task of supporting all that torque for long periods of time. Our Ram's transmission was no exception and was leaking pools of ATF on the ground, even when it was just parked for an hour or two. To make matters worse, second-generation Rams have one of the least-efficient torque converters known to man and will slip at virtually any rpm, at any speed. In talking with the folks at BD, they said the stock converters had roughly a 65 percent efficiency rating, compared with 90 percent or more for aftermarket versions.
We needed a new transmission in the worst way, one that would support the power we were eventually looking to make (about 400 hp at the wheels). With the new BD transmission, we would have a torque converter with a billet front cover, a steel stator, and a 93 percent efficiency rating. The transmission itself would also have increased line pressure through the valvebody and through the PressureLoc system, resulting in more power-handling capability and firmer shifts. While our old transmission worried us at any horsepower level over stock, the new one was rated at a continuous 400 hp, which would be perfect for towing. For our Ram, a performance transmission was the step that opened the door for all sorts of other modifications, so stay tuned as we turn up the fuel in Part 2 in hopes of gaining an extra 100 hp at the wheels.
Jason Taylor from Orange County Diesel agreed to walk us through the installation process, which started with removing the two-piece driveshaft. The shaft was disconnected from the rear axle first, then the middle mount was loosened. After that, the driveshaft yoke was pulled out of the tailshaft of the transmission and the assembly was set aside for later reinstallation. | 
There is nothing that promotes accidents more than a bunch of trans fluid on the floor, so the stock pan was removed and the fluid was drained. | 
Next, Taylor disconnected all the wiring and the shift linkage. Most of the connectors used unique sizes and shapes, so it wasn't hard to remember where everything went when it came time to put everything back together. If you're worried about it, label stuff. It can't hurt. |
The transmission was then supported from the rear, and the crossmember was removed. There was absolutely no way the crossmember could be removed by pulling it straight down (as in many gas applications). It had to be slid back along the frame to a wider section and then pulled out. | 
Torque-converter bolts were next, and they had to be loosened through an access plug located through the front of the bellhousing on the engine side (arrow). A barring tool was used to turn the engine over while the converter bolts were removed. | 
With a jack supporting our transmission, it was almost ready to come out. In our last step, we needed to physically separate it from the engine, so the bellhousing bolts were removed (arrows) with a long extension. |
Use a transmission jack, a regular jack (if you are doing the job in your driveway), a friend, or all three when removing a diesel transmission. With a heavy-duty converter and overdrive, these assemblies weigh hundreds of pounds. | 
With our transmission resting peacefully on the floor, it was time to remove the stock flexplate, which is known to crack at high power levels. We are going to try to get all we can out of our 12-valve, so we addressed the issue sooner rather than later. | 
BD offers a flexplate that's a lot sturdier and is also SFI-approved for drag racing and pulling applications. The flexplate bolts were torqued to the proper specs, and we were ready to put our new BD transmission in. |