I'm going to do a writeup with pics when I'm through just want to make sure Auto Tranny fluid is ok to use. I believe Royal Purple carries this.

 

Yup it uses ATF.I wouldn't use synthetic,but that is just my opinion.

 

Any reasoning for this opinion (not calling you out, just curious).

 

I don't really have any experience with synthetic ATF.So this is a bit off topic.But,I know some people who have had bad experiences using synthetic gear oil in their rear ends.Seems the synthetic is so slippery it doesn't cling to the gears as well and caused clunking.Changed back to regular gear oil and L/S additive and clunking was gone.So I'd just feel safer using what the factory recommends in rearends,trannys and transfer cases.Also my tranny builder for my hotrods doesn't recommend synthetic in his trannys.What any of this has to do with a transfer case,I dunno?However I wouldn't be against using synthetic in the engine.I used Mobil1 for years in the hotrods.But due to frequent oil changes and not seeing any benefits I just run dino oil in them now.I do use Motorcraft syn blend in my truck.

 

well i have had success with royal purple in the rear's but i too have heard bad things about synhetic fluid in tranny and transfercases. i dont know why tho.

 

No problems with Mobil 1 synthetic plus LSD additive for the G80 in my S-10's rearend. YMMV. My .02 Of course, a Ford transfer case is a different animal...

 

In my experience any problem with synthetics in gear applications where it is not specified has to do with them being TOO slippery. I put Mobil 1 in a transmission that called for motor oil and then couldn't shift it. Apparently the synchros, which are really not much more than little clutches, wouldn't get enough grip to match the gear speeds. I switched back to regular oil and it was OK, though it actually took awhile for the film of Mobil 1 to wear off of the synchros! I suspect the same thing happens in an LS rear, which depends on a clutch pack to engage properly. Since there is no clutch or synchro in our transfer cases (that I know of, anyway), I don't know why there would be a problem. Plus, synthetic ATF is made to use in a clutch application in a transmission, so they probably have the friction thing worked into their formula.

 

I do the transfer cases every 30K with plain ole Mercon ATF no problems. Even comes out pretty clean.

Couple tips for ya...

A suction gun makes the job take 10 minutes tops. It looks like a grease gun but just has a hose on the end, and can be found at any parts store for 10 bucks.

Undo the fill plug first so if you strip it you don't screw yourself stranded with an empty transfer case after undoing the drain plug.

I don't know what you have on the new body style trucks, but the older ones have a PITA square drive hole that strips real easy being aluminum, or a allen head. I recommend simple brass pipe plugs you can use a wrench on from home depot.

I fill it as much as possible on the level, then move the truck pointing downhill a little bit to get another squirt from the gun in.

Supermotors is down right now or I could show some helpful pics.

Adrianspeeder

 

Our diffs already have synthetic fluids in em from the factory so there would be no harm in going back with a full synthetic in those, although the transfer case using Mercon V, IDK about.

 

I was aware of the pump method (I have a pump for refill rather than a funnel) and removing the fill cap also stops the "gulping" while emptying the fluid and comes out smoother and quicker than would be otherwise. If you do strip the fill cap you may be able to fill it up via the vent. Thanks for the tips adrien, I'll mention them in my writeup if I do so.

 

the tranny fliud that is in your tranny right now is synthetic... Mercon V

 

x2

Hey J is that what the problem is with your t case, just needs a fluid change or are you just HOPING that's what it is

 

Fluid should be changed every 30K along with an automatic tranny flush. How all my transfer cases shift with little effort. The NP208 in the Lariat took two hands to move when I first got it, and after some fresh Mercon shifts like a toggle switch.

What transfer cases are in the new trucks anyway?

Adrianspeeder

 

The ESOF transfer case is a Borg-Warner, don't know the model #. I wouldn't use anything other than the mfg. spec. fluid for changes. If you have a warranty why give the dealership an excuse to wiggle out of fixing it if something goes wrong? I.E. "You used an unauthorized aftermarket fluid which caused the failure." If it ain't broke, don't fix it. Go with the spec.

 

Mercon V is a blend.Blends have some of the conventional oil characteristics like better clinging abilities than straight synthetic.Kind of the best of both worlds.I don't have issues with using blends in trannys and differentials.I wouldn't use straight synthetc,but I'm sure many have with no issues.