U-joint issues

[76-cj7]

Ok, i know im prob going to be called a dumbass but in my rear drive shaft the 2 caps in the yoke on my M20 keep breaking the needles which therefore cause the joint to turn from metal to a black powder. So twisted yoke maybe? But it's brand new.........its go a Tom Woods rear shatf but the 2 in the slip yoke are perfectly fine but just the 2 in the yoke bust needles. If i run the dogshit out of it the joint will fail in about 3-4 days but if im easy on it they last 2+ weeks.....at least thats how long this ones lasted. I've gotten prety good on changing joints out quick but im tired of buying them, so what the hell? Auto Zone u-joints to blame? The spicer that was originally sent with the driveshaft had busted needles too.

[jeepsr4ever]

Ujoint faliure is mainly caused by a lack of lubrication. If you arent lubing these joints after installing I can see why you have alot of worn out needles. Cheap joints are also a mixed bag. You should buy a good joint and use very heavy sticky grease. Caterpillar had some incredible synthetic grease that was very sticky.

[76-cj7]

Doing all of the above MC.......its getting so bad that i keep 4 spare joints...U-Joints that is.....with me along with a grease gun and needle at all times. Im using a tacky marine grease but i dont think grease would be the problem thou considering its in all of my u-joint and they are good to go......better knock on some wood But what baffles me the most is the only ones i have a problem with are in the yoke on the diff and no other ones But like i was saying before the spicer ones crapped out also. Im betting on the yoke being tweaked, but thats just me.

[hugh]

I,ll just quote some stuff about driveshafts from the jeep performance handbook. Before that, is your 5 lifted ? because that usually increases the driveline angle since 5,s already have short rear driveshaft. Anyway, Spicer rates their U joints for 5,000 hours at a 3 degree angle. At 12 degrees that life is cut down to 25 percent or 1,250 hours. 15 degrees is the absolute maximum continuous operating angularity for U joints. Even a mild lift will put most short wheelbase jeeps past 8 degrees.
If you are running a 2 joint shaft the pinion and t-case outputs should be parallel. If they arent you can shim the rear diff or lower your T case. Another solution is to run a CV driveshaft, in this case the pinion must be parellel with the driveshaft.
Also your grease should be extreme pressure rated, EP 2 is ok

[76-cj7]

I have the Advance Adapters heavy duty rear output shaft along with a Tom Woods 1310 cv style shaft. I had to fab up a new crossmember for my trans so when i made it i built it lower than stock and i also cut and move my spring perches so that the angle on the u-joint at the rear end its pretty much flat.......no angle on the u-joint but the cv takes up for the angle.

[hugh]

it sounds like you,ve got the angles right, so thays prob not causing the u joints to break. How about when you install them? Are you using the straps on the pinion yoke or have you upgraded to u bolts?

[76-cj7]

U-bolt on the yoke with new everything. Im still leaning twords a tweaked yoke.....although the damn thing is brand new!

[JERSEYJOE]

ARE YOU SPRING OVER AXLE? IF SO THIS PUTS A LOT MORE MECHANICAL ADVANTAGE ON THE REAR AND TENDS TO TWIST IT UP ON HARD ACCELERATION. THERE ARE KITS TO CONTROL AXLE WINDUP ON SOA SET-UPS. OR YOU COULD SET THE STATIC PINION ANGLE SLIGHTLY DOWN TO ANTICIPATE THE UPWARD TWIST.

JUST MY 2 CENTS

[runnamuck]

could be tighting the ubolts around the caps to much. crimping the cap and not letting the neddles move resulting in lack of lube. and marine grease is not rated high enough for a ujoint. red amsoil or the syn. cat grease are best.

[76-cj7]

I know its not the grease since all the other u-joints are quite well with it in there and its still spring under axle and as far as over tightenting........i tighten them just the same as all the others ive changed.