No complaints! I can only compare it to my '93 B-series 5.9L and my '78 DD671 (non-turbo)
The ISB wraps like a gas engine. Governed at 3200rpm and I've held it at 3200 for many miles (I know, not the best for the longevity of the motor) but I'm still waiting to find an Allison shop that will unlock my 6th gear. BB will not provide a letter of approval to do so....
The B series was great too! I had an issue with the fan clutch/cooling system, so it was always running hot against the overtemp warning. Ran it like that for 5years and she still runs today. (can't say the same for the P.O.S AT545 that was behind it!)
The DD is fun, takes off like a ROCKET! Sounds like a hot rod! Overheated once, and now I need a re-build or re-power....
I do. It will have to wait though. Getting ready for a trip to the Grand Canyon, and stuck on the rear Fuel Filter replacement at the moment. I loosened the filter to drain it out, and have almost 2gal. drained (not counting the filter capacity) and she's still draining! I have even clamped the fuel inlet and outlet lines upstream and downstream of the filter housing. Where is it all coming from? Will it ever stop?