Drag racing is hard on input...
Drag racing is hard on input shafts. If you're going to be leaving the line hard enough to generate 1.7-second 60-foot times in a 7,000-pound truck, like Tony Burkhart, then you'd better have a fully upgraded transmission. Burkhart did, and he was looking strong at Diesel Power Challenge until a nitrous backfire sent him packing.
11. What are the Dodge transmission's strong/weak points?
Goerend: On a '96 and newer, the line pressure, converter clutch, and converter all need help. In 1996, Chrysler upgraded the front planetary gears and overdrive section, and those were a lot stronger than the '94s and '95s. And, of course, if you're over 500 horsepower, the stock shafts can break.
12. What are the Allison transmission's strong/weak points?
Lovrich: The Allison's weak points are the TCM programming and the converter. It's always learning, which sometimes hurts more than it helps. If you've been driving in city traffic for an hour and then hammer it, the transmission will still be used to low speeds, and you can actually hurt your transmission.
13. I'm going drag racing/sled pulling. Should I worry about my transmission breaking?
Goerend: At stock power levels, it should be OK as long as you don't build too much boost while the truck isn't moving. If you're going to do it regularly, you should upgrade your transmission.
14. What is "stall speed"? Does my torque converter need a lot or a little of it?
Lovrich: It's the max rpm your engine can reach while standing on the brake and flooring it. Diesels like lower stall speeds because they have a smaller power window to work with, and they like their power down low.
15. What's "lock-up"?
Lovrich: It's when a clutch in your torque converter locks up and turns your converter into one big connecting shaft. Good news is that if your lock-up clutch(es) slip or fail, the transmission may still be fine.
16. Why are diesel transmissions so expensive?
Goerend: Number one, the lock-up converter. Parts alone are a lot more expensive for those. All diesel transmissions have an overdrive, so that is an extra expense, too. They're under more stress, so we put all new input shafts and bearings in each transmission. Anything you do to reduce costs will come back to you later.