In November of 2021, I purchased Duramax Tuners 5 to 6 speed Allison conversion kit to install in my 2005 Chev 2500HD that I purchased new back in September, 2004. I have put about 2000 miles on the truck since I installed the kit back in Dec, 2021 when it had about 125,000 miles on it.
I would recommend to anybody who buys this kit to make sure that they have access to a TECH 2 scanner to calibrate the transmission after installing the valve body and the TCM. On the first shift into 6th gear, it felt like somebody had hit the side of the transmission with a sledge hammer as the shift was that hard. After doing some research, I found that the TECH 2 scanner has a calibration function for the Allison transmission. After following the instructions on the TECH 2 to calibrate the transmission, immediately the shifts, up or down through all of the gears were much nicer.
After driving the truck for awhile the shifts became very good whether I have the transmission in T/H mode while towing something or just during normal driving with nothing behind the truck. I think the shifts with the new TCM and valve body are better than what they were with the old TCM and valve body that were in the truck.
I bought this kit specifically to drop the RPMs while driving at 70 to 80 mph in order to quiet the noise in the cab which it does making the driving experience a more positive one. And as a bonus, the calculated gas mileage has gone up about 1 mpg. As well, the pyrometer temperatures have dropped about 100 degrees while cruising at 75 mph due to the lower RPM that the engine is running.
My experience with Duramax Tuners has been a very positive. They gave me good support during the purchase and very good support after. From what I can see of the company, they are a good group of guys that want to deliver a good product at a decent price and are willing to back it up.
I am very impressed with the work that Duramax Tuners did in reworking the software in the TCM and rewiring the later model valve body to work with the LLY platform. There are some very smart people working inside that shop.