I've spent a great deal of time, money and effort to fix what I feel was the weakest link on my truck - the factory automatic transmission. I don't believe the factory transmission was designed to handle the added weight, horsepower and torque of my highly modified truck, especially in a demanding rough road environment.
When I first upgraded my transmission in early 1999, there weren't nearly as many options available as there are today. It now seems like every other company has a low stall speed torque converter for Cummins powered Dodge Rams. Knowing what I know today, I would simply swap out the factory transmission with a high performance transmission and triple disc torque converter.
Initial Tranny Overhaul (TST products)
In early 1999, I had my tranny rebuilt with parts purchased from TST products. Mark Chapple at TST is a retired Cummins engineer and his TST web site is packed with good info. Based on a recommendation from TST, I had Scotty's Auto and Truck in Brighton Colorado rebuild my transmission with the BD low stall speed torque converter, Transgo shift hit, and heavy duty rebuild kit. The parts and labor were expensive (about US $3,000), but this greatly improved my automatic transmission. After the tranny rebuild, my truck accelerated more quickly since I was getting much more torque to the wheels at lower RPMs, and the shifts were firm without being harsh.
Around town and on slow steep climbs the tranny fluid heated up quickly, so I strongly recommend a tranny temperature gauge and auxiliary tranny cooler with this modification. Don't depend on the factory ATF warning light to alert you to high ATF temperatures. The factory temperature light for my automatic transmission has never come on, but my Auto Meter transmission fluid temperature gauge has alerted me to temperatures over 180 degrees on several occasions.
I also installed a Mag Hytec tranny pan which provides increased ATF capacity, a drain plug, better cooling and a hole for the temperature sensor.
BD Engine Brake - more Transmission Upgrades
In November of 2000 I stopped by BD Engine Brake in Abbotsford, BC, Canada to have engine and transmission upgrades installed on my truck. I had BD install their TorqLoc electronic tranny kit, PressureLoc kit and an auxiliary transmission fluid cooler.
The TorqLoc has a 3 position switch that controls torque converter lock up. In the first switch position, the the torque converter is always locked up above 25 miles per hour. This results in quicker acceleration, better engine braking and reduced tranny fluid temperatures. The second switch position converts the tranny lockup to the factory settings. I like to switch to the factory position when it is 20 degrees Fahrenheit or cooler outside to allow the ATF to warm up more quickly.The third position locks up the converter when the exhaust brake is engaged and the truck speed is over 25 mph. Normally, I just leave the switch in the first position to achieve maximum power transfer when accelerating or decelerating
The PressureLoc kit increases the transmission fluid pressure to prevent lock-up clutch slippage when accelerating or decelerating with the exhaust brake. With the installation of an exhaust brake or engine performance upgrades, the PressureLoc will keep the lock-up clutch from slipping.
Before installing the BD TorqLoc and PressureLoc, the ATF temperature would heat up quickly at low speeds with heavy loads when the torque converter was not locked up. As further insurance against ATF overheating, I had BD install their auxiliary ATF cooler. They mounted the cooler under the driver's side cab, and installed both a manual control switch and a temperature switch.