Topic: How (not) to blow up a transfer case

[Quick Draw]

So I was using my truck to transport car parts on my 11 acres of property the other day...  In some places it was snowy and steep, so I was using 4x4 in both 2.28 and 4.7 low with my dual ultimate crawler.  All of the sudden I hear "POP" from the transfer case.  I kinda looked down at the shifter like WTF?  Maybe it was just a fluke...  So I keep driving...again "POP" except this time it binds for a moment.  Okay, now this definitely a problem.  So I dropped everything off at the shed, and parked the truck to deal with it later.  Then I notice gear oil puking out on the ground.  Something had blown out an entire chunk of the rear case near the drain plug.  I finally got around to opening it up and this is what I found:



1 Broken #2 Cover:


1 Broken main shaft bearing cover:


3 Broken gears:


Tons of shrapnel and metal shavings!


The good news is that my take offs for the crawl box provided me with all the spares I need to fix this, so I'm only out some gear oil and sealant.  I was so relieved to find that my expensive Marlin 4.7 gears are OK!




So what happened?  I believe the bolts holding the bearing cover backed out, as I found crunched bolts among the shrapnel.  Why?  I'm not exactly sure...  The instructions call for no thread locker and a torque of 10 ft/lbs, which is exactly what I did when I put it together.  I think when I put it back together, I'm going to throw some red thread locker on the bolts...

Anybody else have any theories on what happened here?

[86toyota]

that would be my guess. other wise how would the bearing cover of come off. did the bolts break off in the hole? glad to here the Marlin gears heald up!!

[Quick Draw [OP]]

Nope, the bolts came out cleanly...  So yeah they had to have backed out.  I guess the only real question is:  How/why did this happen?  And how can I best prevent if from happening again?

I suppose there is a very tiny possibility that I just completely forgot to tighten these bolts down in the first place... But with as careful as I was building these things, and following every single step, I can't imagine such a huge oversight.

[86toyota]

who knows? i havent put one together yet, just getting parts together all i need is the adapter. Does the bolts on the cover use lock washers? if not i wouldnt be that surprised if they backed out. coulda been a little bit of grease on there helping them back out earlier with virbration. Id use locktite for sure 2nd time around. Not gonna hurt anything. it atleast wont do that again

[Quick Draw [OP]]

Yeah...  I'm kinda curious to see what somebody from Marlin would have to say about this.  I mean, I don't blame them at all...  But they're certainly the expert on these things.

[86toyota]

yeah i know what you mean. Call them up 1st thing in the morning. They are all great guys to deal with

[emsvitil]

I think the threads had some gear oil left on them (most likely the holes, not the bolts) and the thread lock didn't have a chance...........

[86toyota]

I think the threads had some gear oil left on them (most likely the holes, not the bolts) and the thread lock didn't have a chance...........

he didnt use thread lock. the instructions said just to torque then to 10 ft/lbs

[Volcom]

Glad to see you were able to salvage what was left from your crawl box leftovers without having to buy another t-case.  Weird breakage for sure.

[axled89]

 

[Quick Draw [OP]]

Well I finally got it all put back together tonight...  It was actually quite funny because I rebuilt it in the elevator lobby of my dorm building.  Soon the rumor that I was building "an engine or something" circulated and I had several spectators in no time.  

So tomorrow I will throw it in the truck and hope that everything is correct.  I still need to wash out some metal shavings...  I did my best to wipe them out, and run a magnet over everything, but there are still some in there.  I was thinking I might throw motor oil in the case, and crawl around for a short distance then drain it out, then put cheap gear oil in, drive for 20 miles, drain it out, and then put in the good stuff.  Does this sound good?

[Quick Draw [OP]]

It's back in the truck and working great!  But now the noises my square driveshaft makes are getting me paranoid.  It was a good thing I got it done, because we got a ton of snow and there would've been no way I could drive my Subaru out.

[86toyota]

where are you at that got alot of snow? CO?

[Quick Draw [OP]]

Yeah.  In the mountains just west of Ft. Collins at about 7500 ft.  There was about 2 feet over the course of about 12 hours.

[86toyota]

nice. Im here in montana waiting for a big spring storm. It happens every year and i cant wait. itll probably happen in june lol

[Redbeard1]

I don't care what instructions say if It is on the inside and I cant see it it is getting some sort of thread locker on it I put it in or together. Especially if it is in gear oil. Cheap insurance for stuff like that but I have also been know to drill and wire stuff like that.

[dgrant71]

Sorry to hear that, use locktite next time

[Quick Draw [OP]]

Hindsight is 20/20....