Stick with regular Mercon/Dexron III or go synthetic?

 

My brother works for Waste Management and after they had several ZF failures back in the early '90's the factory recommended they use 15W-40 motor oil in the transmissions instead of the usually recommended ATF

The box in my '90 F-350 with 148K was a little noisy and I put Mobil One 15W-40 in it and it seemed to quiet things down

You might have a little problem shifting in really cold temps until the trans warms up, but I've not seen that so far with mine . . . . but then it seldom gets really cold down here in Biloxi

Don

 

That is interesting. I spotted something on the web about using motor oil. Up here in South Dakota( being a couple of feet from the arctic circle according to some 'intelligent' weather people) I think a switch to a 0W30 might be a better choice.

 

I have 10w-30 mobil one synthetic in mine. A bit quieter..nothing to write home about tho.