MY transfer case blow up at 70mph
05-28-2012, 06:27 AM
#1
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MY transfer case blow up at 70mph
Hi boys and girls I was wondering if any one else has exprienced there transfer case shattering into peaces . I was driving around 70mph when it happened . The JK has 88k miles on it and if any one has any upgrdes ideas Its a rubicon so I had the 4:1 ratio TC on it . Tkssssss 
05-28-2012, 06:39 AM
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Sorry to hear about this man. I've read a few stories about this happening. If I'm not mistaken, I think it has to do with the pinion angle on lifted vehicles. It typically happens in 2WD and at high speeds. My assumption is that the stock driveshaft is at the wrong angle, and just can't take it. I'm sure someone else will chime in with more info. It's a good reason to upgrade though!
05-28-2012, 06:52 AM
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05-28-2012, 07:24 AM
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The pinion angle with a double cardan ujoint should be zero at the front ujoint which would put your caster at~1° so if you adjusted your caster to 4° to 6° your pinion angle was way off 0° 
That will case vibrations up at the double cardan ujoint which just happens to be at the transfer case 
If you have a 3 or 4" lift it would not be a surprise
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05-28-2012, 07:54 AM
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I think it also has something to do with the higher gear Rubicon trans case?
Sorry to hear about this man. I've read a few stories about this happening. If I'm not mistaken, I think it has to do with the pinion angle on lifted vehicles. It typically happens in 2WD and at high speeds. My assumption is that the stock driveshaft is at the wrong angle, and just can't take it. I'm sure someone else will chime in with more info. It's a good reason to upgrade though!
05-28-2012, 08:09 AM
#9
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Here's a link to a similiar thread.
https://www.jk-forum.com/forums/jk-s...n-fire-171530/
https://www.jk-forum.com/forums/modi...ploded-138605/
https://www.jk-forum.com/forums/jk-s...n-fire-171530/
This is the recipe for disaster:
Lifted
Regeared
After market front drive shaft with single joint at the pinion, double cardan at the t-case
An adapter at the t-case that increases the distance of the double cardan from the t-case.
Front pinion more than a few degrees out of alignment with the drive shaft
Highway speed
That's when you are tooling along, fat, dumb, and happy, (no offense, it's just an expression), then you suddenly hear the onset of vibration. Then, all of a sudden, KABOOM!
It's happened to quite a few JKers.
The thing that would prevent this is getting the front pinion and drive shaft into alignment. The double cardan at the t-case requires the front joint to be in alignment with the drive shaft.
But then, that can't be done on a lifted JK because you would have too little caster.
Lifted
Regeared
After market front drive shaft with single joint at the pinion, double cardan at the t-case
An adapter at the t-case that increases the distance of the double cardan from the t-case.
Front pinion more than a few degrees out of alignment with the drive shaft
Highway speed
That's when you are tooling along, fat, dumb, and happy, (no offense, it's just an expression), then you suddenly hear the onset of vibration. Then, all of a sudden, KABOOM!
It's happened to quite a few JKers.
The thing that would prevent this is getting the front pinion and drive shaft into alignment. The double cardan at the t-case requires the front joint to be in alignment with the drive shaft.
But then, that can't be done on a lifted JK because you would have too little caster.
It's not a t-case design flaw.
The common denominator in the t-case explosions is lifted, bad pinion angle, aftermarket drive shafts, re-geared, highway speeds. I'll even bet the OP's front drive shaft had a single, regular u-joint at the pinion, and a double cardan at the t-case.
This all adds up to hitting a critical front drive shaft vibration frequency, then KA-BOOM.
And the farther the t-case yoke puts the double cardan from the t-case, the easier it will be to hit that frequency.
This is assuming the t-case hasn't seen a trail impact or bent drive shaft.
The common denominator in the t-case explosions is lifted, bad pinion angle, aftermarket drive shafts, re-geared, highway speeds. I'll even bet the OP's front drive shaft had a single, regular u-joint at the pinion, and a double cardan at the t-case.
This all adds up to hitting a critical front drive shaft vibration frequency, then KA-BOOM.
And the farther the t-case yoke puts the double cardan from the t-case, the easier it will be to hit that frequency.
This is assuming the t-case hasn't seen a trail impact or bent drive shaft.
Another thing to consider:
When one replaces the front drive shaft with a shaft that has a double cardan joint at the t-case, the front axle must be rotated to get the front single joint as straight as possible. Trying to maintain caster may prevent that.
Having an angle on the front joint pretty much negates the benefit of the double cardan at the t-case. They are not perfect constant velocity joints. They have their own dynamic issues, and are a source of vibration, too.
When one replaces the front drive shaft with a shaft that has a double cardan joint at the t-case, the front axle must be rotated to get the front single joint as straight as possible. Trying to maintain caster may prevent that.
Having an angle on the front joint pretty much negates the benefit of the double cardan at the t-case. They are not perfect constant velocity joints. They have their own dynamic issues, and are a source of vibration, too.
05-28-2012, 03:28 PM
#10
JK Freak
yup, many people have had this happen. I chose a go with the 4sp atlas, there are other options as well. How do you use yor jeep? The atlas's are very strong, but also tend to be loud. Especially at high speed.