Does anyone else run something other than ATF+4 in their G56 trans?

 

The owners manual call for atf4 and I have used Amsoil ATF before as well. I did not notice a difference over the Mopar so I just use Mopar..

 

Ditto. I felt a marginal improvement in cold weather shifting,but not enough to justify Amsoil's cost. I'll just put some ATF+4 in there next time. The shifting definitely improves with heat. My Walmart doesn't carry Mopar+4 anymore,so I'll just use whatever ATF+4 is on the shelf.

 

I would be curious to see if a light gear oil, say a synthetic 50wt would improve shift quality. I hate the thought of using what is basically a hydraulic oil in a manual trans

 

If the tranny was designed to have this fluid I see no problems with it. I would hate to try to use an oil that is not reccommended! It would be like using a 5W30 in the engine.

 

That's my only comfort, the fact that the factory recommends it. Unfortunately they are slowly but surely turning the truck into a car and compromises are made. I'm sure the trans would be better off with a real gear oil. But is it necessary? No if it will last a long time with the ATF.

Not like 5W30 in the engine, more like synthetic 60 in the engine. Gear oil is a more capable oil for gears. The real question is does the extra margin give a benefit?

ATF has to do so much in an auto trans, gear lube, coolant, and hydraulic oil duties.

Regular gear oil will have higher film strength and EP (Extreme Pressure) additives, and phosphours for brass syncros. I wonder what the G56 transmission manufacturer, Mercedes Benz, uses for this trans in their own trucks. I also wonder how much GCWR they rate the trans for in a real truck.

As long as I stay within the GCWR and lightly modified engine yes I agree with you. Why mess with it? But if I was more modified and towed heavy I think it would help the transmission.