What kind of fluid is used in the ZF-6? I checked the manual and its says "Synthetic Transmission fluid approved by allison transmissions" for the 6-speed manual. Is this right, seems like that is for the allison.

Also, what kind of drain intervals do you guys use? When did you do your first fluid change?

All i know is mine is red. so I would also like to know

Castrol Transynd ATF the same synthetic that's recommended for the Allison. It takes 6.5 quarts.

thanks for the reply.

I've been told to change it at 15000 to 18000 mi.

I haven't checked or changed mine and I have 96k on the truck. Even the manual just says the check the level. I will probably change mine at 100k.