Auto trans fluid

[RMC]

We have a Eagle 10, 6V92 auto trans, Allison 740, 4 speed what is the best transmission fluid to use?

[TomC]

The current Dexron rated, or just look on the back of the jug to make sure it is rated for Allison.  I am using Pep Boys (Gulf oil I believe) generic auto trans fluid that is rated for Allison use.  If you are feeling rich, Castrol Transynd synthetic is the best-it is what we order all our Allison equipped trucks with.  Course regular oil is about $9/gal and Transynd is about $45/gal.  Good Luck, TomC

[NJT 5573]

Shell has a product that is priced between the two oils. It is called Shell Donax TX. It is a Heavy Duty Semi Synthetic. Does anyone remember how much oil stays in the converter when you change?

[TomC]

I doesn't matter how much is in the converter (if I remember-like 2 gallons), since all drain capacities are just for the pan and don't include the converter.  If you do switch to synthetic, a bit of regular oil isn't going to hurt.  In fact, synthetic and regular oil mixes just fine.  What do you think synthetic is?  It is regular oil that has been reformulated to have more consistant molecule size.  That's what gives it more lubricity since all the "ball bearing lubricants" are the same size.  As compared to regular oils that have all sorts of sized molecules in it.  Good Luck, TomC