If you've towed with a Duramax-equipped truck you already know how potent these engines are in stock form. But the 300 hp and 520 lb-ft of torque that once had an amazing effect on your Jeep trailer may not feel that strong anymore now that you're in the market for a bigger trailer or hauling more stuff. We know you don't want to get rid of your truck, so while researching '01-'03 Duramax power upgrades for this issue we think we might have found the solution to your problem at Gale Banks Engineering.
We shadowed the calibration engineers at Banks as they put the finishing touches on its newest GM diesel products, and we even got to drive some of the test mules around the Azusa, California, facility before anyone else. What we found will add a lot more go! and even more whoa! to your tow vehicle.
Exhaust Brake InstallOne of the Duramax test vehicles we drove was equipped with Banks' exhaust brake to facilitate safer, more controlled braking. This butterfly valve mounts in the exhaust stream and can restrict exhaust flow to add compression braking when the system is switched on and the driver's foot is not on the accelerator. To test the effectiveness of the exhaust brake, we made four identical runs down a moderate grade starting at 60 mph with 10,000 pounds in tow. Here's what we found:
First Run: Truck began coasting downhill at 60 mph without the exhaust or the truck's brakes applied. Truck accelerated to over 75 mph due to the trailer weight and we had to apply the truck's brakes to maintain control.
Second Run: Repeated the 60-mph test condition at the top of the hill but this time we squeezed the truck's brakes till about 55 mph to activate the Allison's Tow/Haul mode downshift schedule, and let the transmission do its thing. The truck's speed held to roughly 65 mph with no additional use of the truck's brakes.
Third Run: With the Banks exhaust brake engaged and no use of the truck's brakes the truck held a comfortable 60- to 65-mph speed with a mild burbling sound from the engine and a light whooshing sound from the exhaust.
Fourth Run: Engaged the Banks Brake and applied the truck's brakes till the vehicle slowed to 55 mph. The truck's brakes were then released and the Banks exhaust brake and the Allison's Tow/Haul mode downshifting schedule complemented each other perfectly to slow the truck to a comfortable 55-50 mph.