I did not have any luck finding the Transynd locally or online. I found one shop near my house that wanted $68 a gallon...Ooch!
I ended up finding the Mobil 1 Synthetic ATF at the Lubricant Store. (Link below). The Mobil 1 is one of the Allison TES-295 Approved ATF. See below the list of approved ATFs.
I was able to buy 4 x 1 gallon jugs of it for $208; that included tax & shipping.
From the Allison website:
Remember when seeking a fluid for your Allison transmission that is TES 295TM approved do not fall to the claims of some companies that claim that their product is TES 295TM approved. The statements infer that these products "are designed to meet", "are equivalent to", "meet or exceed", etc.
JohnnyO 2012 Denali Dually HD 4x4
Banks Exhaust, Ram-Air & Custom Super-Scoop
Line-X, BedStep, BedStep2, Bed Rug, PPE deep trans pan.
B&W Turnover Ball Hitch with Companion 5th Wheel Hitch
American Work Cover-rolling cover/toolbox w/ B-light tonneau lighting system
1993 GMC 1500 SLE Extended Cab Short Box, 4x4, 5.7 gas, traded it for:
1996 GMC 3500 SLE Crew Cab Dually, 4x4, 7.4L gas, sold it and got a:
2003 GMC 2500HD SLT Crew Cab Short Box, 4x4, 8.1L gas, traded it in for the 2012.