Ran Transfercase Dry

So my Jeep has become my wife's vehicle and I may have been neglecting its care a bit. Since changing out the ball joints where has been a bit of a noise (I always attributed it to possibly a fan clutch gone bad, or some other vibration that was not critical. I checked all the bolts and fasteners I touched during the ball joints along with other areas I thought it might be.

Well time went on where my wife was driving it more exclusively. I drove it the other day and it started getting bad enough I pulled over to check. front end had no play. it felt like it was coming from either the engine bay or the middle of the car until vibrations made it known it was coming from the transfer case. I put it in 4WD (while traveling straight on a paved dry road) and the vibration went away. I attributed it to possibly not fully moving the arm on the 4WD select.

I pulled the plug as soon as I could and found out the transfer case was bone dry. I filled her up with DEX III/MERCON not knowing where the leak was, and after a small trip to the part store to pick up some more fluid there was a puddle. after a 45 min drive back home the whole undercarriage was covered with fluid. So needless to say there is a fairly massive leak out the rear output shaft seal.

I have a new one on order. I have some DEX 6 to fill it up with. I do see metal shavings in what is dripping from the transfer case.

My question: likely how much damage is done when there was both audible and felt vibrations from the transfer case? Is there a pump in the transfer case that could have been damaged running dry? Should I replace the seal run the fluid in it for a few hundred miles and then change it out again (like get a qt of Dex III for the temp fluid...)? Any way I can inspect the transfer case with out pulling it can cracking it open?

Thanks for the help!

I'm not sure what could have been damaged and caused the metal shavings, but if it were me I would just start shopping around for a used transfer case.

I think it is just from running a rotational gear assembly with no lubrication. If I remember also there was some sort of pump (from when I was looking at a slip yoke eliminator and the install process.

you probably stretched the chain and rounded some teeth

the little gerotor oil pump may be damaged too

if the other seals ran dry then they are probably shot too

sounds like a total rebuild

The bad thing in your case is that the 231 does have an internal oil pump to keep the bearings and chain lubricated. Aside from the pump running dry and generating metal shavings as it self-destructs internally, all of the bearings ran dry and will also be on the way out (the noise and vibration you noticed) as well as the chain wearing.

The good thing is that a 231 is really easy to rebuild and the hardest part is simply pulling it out to get it on the bench. New bearings, seals, chain and an oil pump will set you back about 250-300 bux depending on where you shop. You've got several driveline shops in your region that will have the necessary parts in stock.

Also on the plus side, if you have ever considered putting in an SYE, now is the PERFECT time to get it done.

Well looks like my over time on my check will go towards this and not to the new 55" curved 4k TV I wanted to get....

A standard front drive shaft will still work as a rear drive shaft with the SYE right?

If you still have the AW4 in your sig, it should

Yes I do.

Also guess will anything bad happen if I limp it along? if the seal keeps the fluid in the case other than knowing I have cut the life in half on the transfer case nothing catastrophic will happen when it fails will it? its not going to kill the transmission? it will just tare to bits and I wont have any drive right?

its directly attached to the transmission, so theoretically it could lock up and result in big damage

is it still making vibrations? noise from the chain is no concern but if parts are moving around freely that would be an issue for me

maybe buy another to run temporarily while you rebuild the original, then sell the extra later

Once I put fluid in it all noise and vibration stopped. until I change the seal I am not sure how well it will hold fluid.

You really need to pull it apart and do a full inspection or you may be sad about the results.

Stuff I bet died:
- range and/or mode fork plastic pads and possibly the forks themselves. In fact that is where the metal in my run-dry NP231's new fluid came from, the pads melted and then the forks rode on the shift hubs directly and got ground up.
- you may have overheated and detempered a number of bearings and bearing surfaces in the case. It takes less heat than you would think, and they heat up fast when not cooled by the fluid.
- could have ruined the pump, or at least the seal on the pump.
- possibly stretched the chain if it's been run in 4x4 like this, but probably not if it was just rolling around in 2wd.

I'd plan on a full rebuild or at the very least, an input bearing, shift forks and collars, pump, output housing bearing, output seals front and rear, and the bearings that support the front output shaft at each end. Probably easier to go with a new used case and keep this one around for parts or eventual rebuild/SYE install.

If you need to keep the vehicle going, I would consider buying/borrowing another t-case to swap in. And rebuild the current one.

T cases at PNP are like 75$ ?

I pulled the old seal off there was no play or wiggle room on the output shaft. I drained the fluid that I had put in and used an air compressor to try to drain it as much as possible.

inspection of the fluid that came out did not look bad other than what you would mostly expect ATF fluid to look like after 5 years of use in a TC. there was some metallic shimmer to the fluid but not as much as was by the seal. I think what might have been the over metallic look was I used anti seize on the inside spline of the shaft so while the seal was leaking and fluid was getting in it was mixing with the anti-seize and giving it a more silver metallic look.

Replaced the seal, topped it off with some health DEX VI and drive it around a little bit. Put it into 4 wheel HI and LO and it transitioned about as well as it normally does between the selections. I will keep an eye on it and plan on a rebuild in the future and next time I am at the JY will look for a transfer case.

Well finally got around to replacing the transfercase.

I the chain was now so loose that it was rubbing along the aluminum case at the bottom and started putting small holes in it. JB weld fixed it till i could get to the Junk yard and pull a new TC.

This is what the view was like from the fill port:


https://youtu.be/k4DB-a635MQ

And I now know what quick silver would look like. the fluid that came out looked like liquid silver due to how much metal was in the fluid.

New case is in. the Chain is nice and tight. all 3 modes work (2WD, 4WD-Hi, 4WD-Lo) and runs well again. unfortunately due to time and budget was not able to install the slip yoke eliminator this go around.

Ive had an np231 lock up on the high way from being ran dry... It locked itself into 2wd low range (fun at 80mph). It damaged the range shift fork, locking it.