I would let them do it. The way it is calibrated now, C3 and C4 are applied which puts the Alli in 2 gears at once ( bound up ). This puts a load on the converter and heats up the fluid quicker. TCM reads its temps from the sensor on valve body so when the fluid warms up in the pan the TCM says you're good to go. Problem is; Dex 6 freezes at -40F ( sooner than Dex 3 or synthetic ) and solidifies in the trans cooler , which is a stacked plate design and won't allow fluid till it heats up and expands these plates. Fluid cannot escape out of the converter which will overheat badly, and this fluid that should be flowing from the converter into the cooler leaves the geartrain totaly dry because that fluid IS YOR LUBE.
You are screwed. Dex 6 was never tested in cold weather. I never liked Dex 6 and neither did Allison. This was GM bean counters call to do this. Dex 6 does not allow your clutches to hold as well as TES 295 fluid ( TranSynd or its equal ). Some people take the owners manual as the holy grail and swear by Dex 6. If you are one of these people, at least go out there and buy synthetic Dex 6 so you stand a chance in freezing weather.
