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TJ Rear driveshaft solution.

5K views 9 replies 8 participants last post by  Sulaiman~Oman 
#1 ·
Hey all,

I have a recurring issue with my 99 TJ rear drive shaft coming apart at the rear differential.

I bought my truck a year ago. It has a 4" suspension lift and a 2" Body lift.
I was offroading last August and Broke the clamp that holds the U-joint to the rear yoke. I bought new straps and Ujoint, replaced them and essentially fixed the problem. The person who did the lift did not put in a new longer driveshaft to compensate for the lift. I ended up wheeling again and the play in the driveshaft snapped the transfer case in half.

I got the transfer case replaced and got a longer appropriate drive shaft to replace the shorter one. Everything was lovely until.......

I was doing very light off-roading and the Caps on the ujoint came free and my driveshaft fell off again.

http://s14.postimg.cc/rjuek09dd/IMG_7203.jpg
http://s17.postimg.cc/ogfankyf3/IMG_7201.jpg

What do I do to fix this? It seems like a weak point and I don't want to have to do this everytime I hit a small bump.

Any recommends for a good jeep guy on the south shore, MA would be welcomed.

Thanks
Joel
 
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#3 · (Edited)
Your repeated rear u-joint failure is nearly undoubtedly being caused by an incorrect rear pinion angle from such a tall lift caused by the previous owner not having installed a SYE kit in the transfer case and the proper longer length aftermarket CV driveshaft.

Few know how to properly set up the pinion angle and many totally jack up the rear axle's pinion angle trying to "correct" it after installing a 4" lift. Also, 4" is too tall of a lift for the rear driveshaft which is too short for that tall of a lift.

The only good fix is to install a SYE (slip yoke eliminator) kit into the transfer case which will allow the use of the proper aftermarket CV (constant velocity) driveshaft which adds a 3rd u-joint so it can handle the steeper drivetrain angle caused by the 4" suspension lift.

You'll also need adjustable length upper rear control arms so you can raise the pinion angle to properly meet the needs of the new CV driveshaft.

Tom Wood's Custom Driveshafts would be a good source for the SYE kit and CV driveshaft. Tom Wood's Custom Drive Shafts - Tom Woods Custom Drive Shafts Custom Driveshafts Specialist

Your future pinion angle would look like the first image where the pinion angle needs to be the same as the driveshaft.

Your current pinion angle should look like the second image. The pinion angle is supposed to be parallel to the transfer case's output shaft.
 

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#5 ·
I have minimal vibration. Not any more than you'd expect from my 33's. I think the SYE will be my next step. It is pretty costly, but if you think that's what will solve this issue. That's what I'll do.

I have infant twins so I have little time to do these mods on my own. I was hoping someone knows a good shop that will do a good job and understand Wrangler stuff on the south shore.

PS Shark, those shift knobs are sick. I am getting one.
 
#7 · (Edited)
I have minimal vibration. Not any more than you'd expect from my 33's. I think the SYE will be my next step. It is pretty costly, but if you think that's what will solve this issue. That's what I'll do.
4" of suspension lift is where a SYE and CV driveshaft becomes pretty much required. Not to mention the factory driveshaft is too short for that much suspension lift height and in some twisted up trail conditions it could be pulled completely off the slip-joint on the transfer case output shaft. Or worse, be only partially pulled off and cock at an angle instead which can bend the tcase output shaft as the rear suspension recompresses and the axle tries to push the cocked driveshaft's slip joint back forward onto the t-case output shaft.
 
#9 ·
From your pictures I can see one cap still in the yoke. On the side that the cap is missing, are the bolts still tight? If they aren't, did you use locktight on them when you put in the new caps? Also, normally there is a 'nub' on the bottom of the half-loop (socket) of the yoke. It sits on the outside of the u-joint cap when the u-joint is installed and you should be able to see it on the cap that is still captured. Is it still there on the side with the missing cap or was it broken off on the 1st u-joint failure? If the 'nub' is gone, the u-joint cap can slide outwards (and off) under the centrifugal force of the driveshaft spinning. If it is gone, then your yoke is FUBAR and needs to be replaced.
 
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