Transfer Case an 30W?

This weekend I had the 231 transfer case apart installing Tom Wood's SYE in the $50 XJ. This was my first ever adventure into a 231, what a simple mechanism. Several years ago I rebuilt the Borg-Warner 1399 full time quadratrac and converted to a part-time case, no more clutches, no need for the special "Jeep" only TC lubricant. I put in Castrol 30w and drove it for close to 40K miles before selling it with no problems.

So while I had the back case off and had the synchronizer/chain sprocket out and apart I began thinking, why ATF? I looked in the front case still in the XJ and noticed the front drive sprocket and planetary gear set, but still no clutches. The only moving mechanism I noticed was the spring driven synchronizer that slid the brass piece for locking the chain sprocket into 4wd.

• So why ATF?
• Couldn't 30W or any heavier weight than ATF be used?
• Has anyone tried this?

Thanks,
Tom

While you could get by on a 10w oil,even that would get a little thick in cold temps.ATF is what the pump was designed for and many have cases that last for several hundred thousand miles with no problems.
I have seen a bulletin about mystery fluid loss in 231,s under special circumstances-- the cure was to go to a 10w oil.
Wayne

I wrote New Process many moons ago asking the same question. They never bothered to answer that one. Though on other occasions they have sent me some fairly impressive packages of info (I guess form the public relations people). The reason they supposidly starting using ATF in the first place was because of the lower drag. Some of the early stick shift trannies delivered with ATF (early 80's), actually recommended changing to 30 W, if the tranny got noisey.

My dad had a 3/4 ton 82 chevy with a 208 transfer case and had a seal problem in bfe wyoming with only 20,000 miles on it he put 80/90 in the transfer case and I traded it off with 285,000 on it last year ....we never even replaced the chain in it....never split the case for anything

Do you suppose going with slightly thicker oil than ATF would be good for sealing small leaks? ATF is just so darn thin, leaks seem to be inevetible. I have 131k+ on a NP242 and while it works fine it has a leak that I would like to seal without taking the whole thing apart. Is there a "stop leak" type product that will work on a transfer case without causing more harm than good?

ive got 228,xxx on my np242 in my jeep that has 221,xxx on it. ive noticed fluid loss around the rear output seal on the slip yoke. ive drained and added new atf several times hoping the new fluid would solve the problem, but to no avail. so, as asked in a previous post, would switching to a heavier fluid/oil "clog up" small leaks?

ATF is motor oil with a different additive package, mostly to allow better engagements of clutches (not in an engine) and to withstand the heat/pressure of the Torque Converter. Not sure if that helps.

Its 6 of one, a half dozen of another, I think its wiser to stick to the Recommended Fluid or a Suitable substitute that has the same features as the recommended fluid. Engine Oil does not have the same features as ATF.

I would imagine going with Motor Oil might have an effect on clutch/cone engagement type devices in the XFER Case. You might have trouble getting the thing into 4WD or 4WD Low.

Take that with a grain of salt, I have absolutely no experience with Transfer Cases.