Causes for grenaded T-case?

[m.dolomieu]

Crossposting from Reddit:

Hey all, maybe a stupid question, but are there any common/likely reasons my T-case grenaded? I recently replaced the fluid with Mervin LV, checked the level by dipping my finger in the fill port. I torqued the fill plug to 18lbft per the shop manual. There was some teflon tape on the fill plug from the previous owner; is it likely that I over torqued the fill plug because of the tape and heat expansion between the plug and case caused the crack? T-case exploded pulling away from a stoplight shifting between 2nd/3rd. Had driven about 25 miles @ 55mph. New fluid had about 150miles on it. This is a BW1354 off an 07 FX4 Level II w/180k miles.


Looking for a way to identify the root cause before I drop a new T-case in and have this happen again.

TIA

 

[superj]

wow!!

i have never seen something like that happen. thats crazy

 

[rusty ol ranger]

Did you get any vibration beforehand?

Kinda looks like maybe an output bearing went and let the shaft slop around causing the crack?

Either way it was probably an issue with the T case itself and a different one probably wouldnt be in any danger.

 

[sgtsandman]

That's a new one on me. While the fluid wasn't correct, it shouldn't have caused that.

As guessed above, I would guess there was a catastrophic failure of a bearing.

 

[rubydist]

I would take a very careful look at the u-joints. I had a bad u-joint on an Expedition that got stiff and sticky, and that took out the output bushing in the transfer case and caused all kinds of havoc until I sorted it all out.

 

[19Walt93]

I've seen damage caused by people who thought 4wd and awd were the same driving on pavement in 4x4. Mismatched tire diameter can cause problems, too, but not usually that severe. You would notice the truck lugging down and a dragging sensation way before a major failure, though. Unless the specs have changed since I retired in 2017, Mercon LV doesn't belong in a transfer case, it used to me Mercon/Dexron III which was replaced by a dedicated transfer case fluid that met the same specs(and cost a lot more). I used Valvoline's Mercon in my 2011. Hard to imagine it would cause a problem in 150 miles, though. Time to tear it down and inspect the parts- including the ujoints as mentioned above.

 

[sgtsandman]

I've seen damage caused by people who thought 4wd and awd were the same driving on pavement in 4x4. Mismatched tire diameter can cause problems, too, but not usually that severe. You would notice the truck lugging down and a dragging sensation way before a major failure, though. Unless the specs have changed since I retired in 2017, Mercon LV doesn't belong in a transfer case, it used to me Mercon/Dexron III which was replaced by a dedicated transfer case fluid that met the same specs(and cost a lot more). I used Valvoline's Mercon in my 2011. Hard to imagine it would cause a problem in 150 miles, though. Time to tear it down and inspect the parts- including the ujoints as mentioned above.

The Mercon LV could be a misinterpretation of online information or just plain bad information. The 2019+ Rangers call for LV in the transfer case and ULV in the transmission.

 

[Snoranger]

I’ve dumped a quart of 15w/40 oil in a 13-54 to get home from off-roading 2 states away. The wrong fluid didn’t cause that.

 

[Shran]

Agreed with what everyone else said about the fluid not causing that problem. I don't think your fill plug caused it either unless you set it for 180ft/lbs by mistake or something like that. I don't even torque them, little past snug is good enough. I think all that is just a coincidence. Are you sure that you actually put fluid in it and that it was full? Didn't accidently leave it empty? Mistakes happen.

Were there any noises/weird issues going on before this happened?

The fluid dripping out of the crack and off your wiring harness looks like it has a lot of metal floating in it, my guess is a bearing failure... you'd think you would hear something or feel a vibration long before this happened though.

 

[m.dolomieu]

Did you get any vibration beforehand?

Kinda looks like maybe an output bearing went and let the shaft slop around causing the crack?

Either way it was probably an issue with the T case itself and a different one probably wouldnt be in any danger.

I'm thinking this is what happened. I drove for probably another 10 miles before I even noticed this crack. I heard a pop like I had run over a piece of wood and kicked it up into the undercarriage or something, but did not notice any strange vibrations or sounds before/after it blew up.

For reference, this is a new-to-me truck that I just finished replacing the motor with a reman and rebuilding the 5spd in. I've only put a total of about 300 miles on the truck since the new motor was dropped in. When I drained the case, the fluid was completely silver, but I wasn't sure if that was some kind of friction additive or not. As for the Mercon LV, that's what was cross-referenced from my 2007 shop manual, but I think the part number in the manual was for Mercon ATF, not LV/V. I assume there is a tech bulletin out there probably updated the guidelines when ATF got obsoleted, but I made a bad assumption that LV = ATF.

Good news is that I bought the truck to learn more about maintenance and especially 4x4s, unforuntately I chose to learn the hard way lol...

 

[rusty ol ranger]

I'm thinking this is what happened. I drove for probably another 10 miles before I even noticed this crack. I heard a pop like I had run over a piece of wood and kicked it up into the undercarriage or something, but did not notice any strange vibrations or sounds before/after it blew up.

For reference, this is a new-to-me truck that I just finished replacing the motor with a reman and rebuilding the 5spd in. I've only put a total of about 300 miles on the truck since the new motor was dropped in. When I drained the case, the fluid was completely silver, but I wasn't sure if that was some kind of friction additive or not. As for the Mercon LV, that's what was cross-referenced from my 2007 shop manual, but I think the part number in the manual was for Mercon ATF, not LV/V. I assume there is a tech bulletin out there probably updated the guidelines when ATF got obsoleted, but I made a bad assumption that LV = ATF.

Good news is that I bought the truck to learn more about maintenance and especially 4x4s, unforuntately I chose to learn the hard way lol...

Thats really strange you got no warning.

But no the oil in the t case shouldnt be silver

I would check the u joints too...didnt think about that one earlier.

Drop the driveshaft and spin the yoke and see if its crunchy....and since the case is garbage now anyways dissasemble that bad boy and see if you can figure out what went.

.....and take pics of the carnage.

 

[m.dolomieu]

I've seen damage caused by people who thought 4wd and awd were the same driving on pavement in 4x4. Mismatched tire diameter can cause problems, too, but not usually that severe. You would notice the truck lugging down and a dragging sensation way before a major failure, though. Unless the specs have changed since I retired in 2017, Mercon LV doesn't belong in a transfer case, it used to me Mercon/Dexron III which was replaced by a dedicated transfer case fluid that met the same specs(and cost a lot more). I used Valvoline's Mercon in my 2011. Hard to imagine it would cause a problem in 150 miles, though. Time to tear it down and inspect the parts- including the ujoints as mentioned above.

What is the correct fluid these days for a transfer case on these trucks? The tech pages say Mercon ATF, which I assume is Mercon V or equivalent? Or should I be using XL-12?

Also, I put brand new BF Goodrich KO2s 31x10.5 as the truck had from the factory, but I will double check that I didn't put the wrong size on somehow. Definitely going to inspect the u-joints when I get the truck back too.

 

[rusty ol ranger]

What is the correct fluid these days for a transfer case on these trucks? The tech pages say Mercon ATF, which I assume is Mercon V or equivalent? Or should I be using XL-12?

Also, I put brand new BF Goodrich KO2s 31x10.5 as the truck had from the factory, but I will double check that I didn't put the wrong size on somehow. Definitely going to inspect the u-joints when I get the truck back too.

wrong size tires wouldnt of caused that.

 

[m.dolomieu]

Agreed with what everyone else said about the fluid not causing that problem. I don't think your fill plug caused it either unless you set it for 180ft/lbs by mistake or something like that. I don't even torque them, little past snug is good enough. I think all that is just a coincidence. Are you sure that you actually put fluid in it and that it was full? Didn't accidently leave it empty? Mistakes happen.

Were there any noises/weird issues going on before this happened?

The fluid dripping out of the crack and off your wiring harness looks like it has a lot of metal floating in it, my guess is a bearing failure... you'd think you would hear something or feel a vibration long before this happened though.

I used my pinky finger as a depth gauge and fluid was about 3/8-1/2" below the fill hole, iirc the spec was somewhere in that range per my shop manual. I definitely didn't leave it empty, but I have been addressing leaks as I find them since this is a 17yo truck. I assume I would've noticed if that amount of fluid (1.2L?) went missing, but leave no leaf unturned lol. I have been driving with my windows open, so there might have been a noise/vibration associated with it, but I've only driven this truck maybe 300 miles, so I'm still learning what is normal/abnormal. Definitely did not hear any screeching or loud vibration that couldn't be mistaken for road noise with A/T tires. You are right about the fluid, the old fluid and what looks to be remaining of the new fluid were very silver-y.

 

[Shran]

Gotcha... I would have been very worried about the original fluid coming out silver, that probably would have been grounds to pull it & inspect everything.

Sounds to me like whatever caused this was probably in process for quite a while before you got it and would have happened anyway - your changing the fluid had nothing to do with it.