Some ATF+4 are synthetic depending on the brand

 

Meant as far as tier level.

 

Lazarsmith pretty much built my whole truck (minus what I had already done) from the shortbed to the engine to the Gorilla-56 that resides under it. I have had the honor of getting to know Mike pretty well he is a very smart engineer. As for why its good for the g-56 because it was designed from the ground up to be ran in it. Instead of AT-4 being designed for an automatic transmission. I dont think any engineer is going to tell you exactly whats in his product why because bottom line is someone else will steal it. Watching it hold up in several 700-1000hp trucks was enough for me. To coorsman gorilla juice would be my first choice ,but I wouldnt be afraid to run amsoil in it either

 

A "better" choice in a manual transfercase is a manual transmission lube like Amsoil MTF, Redline MTL (what I run in mine), Royal Purple SynchroMax, etc...they are similar to an ATF in viscosity, but have better amounts of EP additives for gear-to-gear contact.

I changed over about 150k miles ago, started with RP SynchroMax and changed to Redline MTL about 40k ago...I sit with 255k on the clock.

I would not run this in an auto/viscous coupler transfercase, but it seems to work well in my 2004.5.

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Is this similar to the GM version..."Grape Juice"? My buddy with a 1500 Silverado drained his transfercase and it wasn't ATF...a little research on the GM forums called it "Grape Juice", although no body knows what it is.

I know for a fact my transfercase did NOT have ATF+4 from the factory...it was a grape juice purple and thicker than any ATF. I bought the truck new with less than 50 miles on the clock...so I know it wasn't something someone else put in. It looked a lot like the Royal Purple SynchroMax I later installed, but unfortunately that happened a couple ATF+4 changes later and I couldn't really compare the two.

 

The grape juice sounds like a Royal Purple thing. At least that would be the correct color combination. I've been telling people to use synchromesh in the trannies that call for lighter fluids for years. Some people just seem to get get stuck in gear so to to speak, and refuse to use anything but the motor oil or ATF that was specc'd for it when they were made back before synchromesh became available.

I ran the Royal Purple Synchromax in my 1st Gen's Getrag for 50k miles and it did great. Changed it out just the other day. Fresh fluid makes a noticeable difference after awhile. I mix in a quart of Lucas StopSlip to beef up the 7-quart fill with my coolers and outboard pump-driven filter that holds over a quart itself. I think I can run that fill for 100k, no problem. I know when it's time to change just by how the synchros feel. Fluid makes that much difference when done right.