Just for fun - this is a picture of the output shaft of one of my jeep transfer cases.


And the rear axle shafts


4wd can be tough on parts if there is no slip.

 

From the OP per the dealer;

Story: Front diff pinion bearing seized, pinion then twisted off. Then the front drive shaft hit the engine mount bracket and tweaked and split the transmission case. The drive shaft also hit the engine oil pan and made 2 dents on the side of it. The pinion got jammed in the ring gear and cause the front differential case to split. The front differential got so hot from the seized pinion bearing that the fill plug and the wiring harness closest to the front diff melted.

I don't see how the pinion bearing would get so hot if the transfer case failed or if the pinion gear just snapped. Sure sounds like the root cause is a seized bearing and I don't see that being caused by being in 4WD at high speeds.

 

This thread is fun.haha.

 

I don't see a diff housing getting hot enough to melt a fill plug from a failing bearing either

 

Hey oldjeep, what xfer case is that? It doesn't look like my D300

One of the things I taught my son when I bought him his own CJ, "go ahead, leave it in 4wd. Just don't come get me when the damn lever won't move!" He learned.

 

D18 out of a 46 CJ

 

That looks like the kind of damage from rock crawling when a wheel gets sudden traction on a rock, or some one jumped a truck in 4WD.

 

Really? Isn't the bearing pressed on the shaft, so if the bearing freezes, now your forcing the 2 parts that are pressed together to rotate. I could see how that would get scorching hot very quick. Those rubber plugs are soft and pliable. Unless the wiring was touching the case, I dont see how that would melt though.

 

Or you are running 37's with a welded diff and operate the throttle like it is an on/off switch

 

Possible, but in every instance I've seen - as soon as the bearing welds itself to the race then the pinion snaps. Having welded on a lot of diff housings I cannot see how you would ever generate enough heat to get to a plug on the cover before everything exploded.