Rear diff oil boiling - are the shafts screwed?
Thread Starter
JK Newbie
Joined: Mar 2013
Posts: 8
Likes: 0
From: Mississauga, Ontario
Rear diff oil boiling - are the shafts screwed?
2012 JKU 3.6l auto, approx 140k miles, stock rear d44, Yukon air locker, 4.56 gears, general grabber 37x12.5/17 tires.
Long story, short version - new chromoly axles because I snapped one recently rock crawling. The shop replaced the axles, but mentioned that the locker was wedged in way to tight, he had never seen one this tight, couldn't get it out, had to use 2 pry bars and a spreader. The locker was installed about 6 years ago - no issues other than air leaks in that time. I drove home about an hour at highway speeds (60mph). When I got out, the rear was making a weird crackling noise - the diff oil was boiling, the cover was smoking and was completely covered in black - what I assume was the RTV sealant, which was also dripping from the bottom of the diff. So, I now need a new locker at the least, the shop is suggesting a complete new axle. My main question is - are the new axle shafts pooched from the heat, has it hardened the metal, and/or making it more brittle? I don't want to spend at least double the amount on an entire axle if possible, the jeep probably has a few years left in it (rust, motor overhaul, generally things stop working...). Anyone had a boiling diff and what did you do to fix the issue? TIA!
Long story, short version - new chromoly axles because I snapped one recently rock crawling. The shop replaced the axles, but mentioned that the locker was wedged in way to tight, he had never seen one this tight, couldn't get it out, had to use 2 pry bars and a spreader. The locker was installed about 6 years ago - no issues other than air leaks in that time. I drove home about an hour at highway speeds (60mph). When I got out, the rear was making a weird crackling noise - the diff oil was boiling, the cover was smoking and was completely covered in black - what I assume was the RTV sealant, which was also dripping from the bottom of the diff. So, I now need a new locker at the least, the shop is suggesting a complete new axle. My main question is - are the new axle shafts pooched from the heat, has it hardened the metal, and/or making it more brittle? I don't want to spend at least double the amount on an entire axle if possible, the jeep probably has a few years left in it (rust, motor overhaul, generally things stop working...). Anyone had a boiling diff and what did you do to fix the issue? TIA!
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Joined: Dec 2018
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From: Calgary, AB, Canada
Hard to tell what is wrong. Perhaps when you dismantle the diff you can inspect the spline ends for signs of discolourizing. I would say they are ok as they are heat treated way hotter than you got that diff. Also what oil did the shop put in that fixed the broken axle? You may have had EP (Extreme Pressure) type oil in there if the gears were meshing tight. Only way to heat the oil is to boil it in the mesh of gears. Should only get warm to mild hot to the touch in normal operation.
Thread Starter
JK Newbie
Joined: Mar 2013
Posts: 8
Likes: 0
From: Mississauga, Ontario
I ended up speaking with a mechanic yesterday. They had the same opinion that the shafts are not likely damaged.
the original mechanic has left the country for Christmas so I don’t know what oil was put in. It’s a Yukon zip locker so regular oil is all it needs.
I was thinking of replacing the locker anyway because it seemed to be difficult to unlock a few times this past year so I’m going to do that. I didn’t want to spend the money on a complete axle (one of the suggestions from the mechanic) although that would have definitely “fixed the problem”.
Thanks.
the original mechanic has left the country for Christmas so I don’t know what oil was put in. It’s a Yukon zip locker so regular oil is all it needs.
I was thinking of replacing the locker anyway because it seemed to be difficult to unlock a few times this past year so I’m going to do that. I didn’t want to spend the money on a complete axle (one of the suggestions from the mechanic) although that would have definitely “fixed the problem”.
Thanks.
