I presently have an '02 Chevy K2500HD re: my sig with the Allison 5 speed tranny. It has Dexron III in it right now. Today I'm having it drained and flushed. I was wondering can I use Dexron VI (synthetic ) instead or do I have to stick with III? Also would it be a good idea to do a "pan-off" cleaning as well?? Thanks.....................SWH...:)

TranSynd or Mobil1 Delvac ATF are Allison TES-295 approved and the best fluids to use, especially if you do heavy towing or see -40 temps. Your Allison Transmission came with Dex3, to find this look now for Dex/Merc labeled fluids with an Allison TES-389 approval. GM says that Dex6 is compatible, while Allison provided a serial number break in 2006 for allowing use of Dex6. You decide.

OK, I just got back from the stealership after have my Allison flushed and the internal & spin-on filters replaced and here's what they told me. It seems that all Allisons that are brought in for a major flush, such as I had done, will have the Dexron III replaced with Dexron VI. The decision I was looking for was made for me. To easy. Just thought y'all would like to know................SWH...:)