That might be the answer I was looking for in my position not to use ATF.
Is there a 30wt ATF?
The manual for our G749 states that 30wt non-detergent oil is used in warmer temperatures and 10wt non-detergent in cold.
If the warm climate fellas are using ATF in summer, would heat become a problem? I'm smelling a pro and con list in the works. with price comparisons and results. We know these transmission don't like heat.
So far we had success following the manual in some trucks and using a product called hy-trans in the newest build a few years back. That truck is working in the bush hauling logs and dead deer without skipping a beat.
I see that hy tran is knocking on $80 for 5 gallons and I need to fill my barrel since there is not much in it. Have been pricing oil and $79 for hy tran-- $53 for NAPA oil--$50 for O Riley oil premium tractor fluid and $36 for WalMart tractor fluid. I am toying around the best thing to do but I ...
www.redpowermagazine.com
That link had some prices so when time allows I'll dig up other costs for ATF and non-detergents for comparison.
The latest truck that we're just starting on has red fluid in the transmission that smells like ATF. Since it came from a pig farm, that fluid could be anything on the shelf that topped up the transmission.....you know farmers. I might get a chance to run it a bit before I go back to what the manual says.
With all the new products out there it's just responsible to make sure the manufacturers understood the internals of the Hydro-matic GMC before dumping their fluids inside. Non-detergent 30wt could have equivalents but after 60 years of running with it, hard to break old habits.
ls 
