I am having problems with rear u joints failing. Any suggestions on correct pinion angle? Im on stock leaf springs.

 

 

Like above, use an angle finder and check the angles on the transmission yoke and pinion yoke they should be the same.

Paul

 

That makes me feel better, my axle pinion is pointing in an upward angle and I was worried it had to be level

 

Me too Reed. I was wondering the same thing.

 

Stop taking off like a bat out of hell. LOL

 

Thanks for all the responses. I'm at 2 and 2 degrees now . My vibration starts at around 70. First thought it was tires so spun balanced off and on the truck. No help. This last set made it 2900 miles before they went metal to metal. Going to recheck angles this week. Is it possible the springs wrap under increased wind load ?

 

One of the biggest reasons for rear u-joints to fail prematurely is over tightening the u-joint clamps. It is easy to over tighten them which distorts the caps. I can't give you a torque spec but they only need to be tight enough to not come loose. It is pretty common to really crank down on them.

 

i may hear some flak for this, but, in my opinion the angle should be more like 6 or 7 degrees. 2 degrees is so close to straight that bearings are not spinning correctly in caps. if rear is twisting under load, this would cause joints to possibly be dead straight. not good. i would check the driveshaft for trueness and balance. it has weights on it. possible one has left the shaft.

 

Absolutely. It's not so much a question of "if" as it is "how much". Any live axle will wrap to some degree under torque and a leaf spring will allow more wrap than any other suspension design. It's common to intentionally leave the pinion pointed down an extra 1 to 2 degrees so that it will wrap to the correct angle as you're going down the road.

I completely disagree. Any universal joint's life span is directly proportional to its operating angle. The more angle it has, the shorter it's life will be. The normal operating angle LIMIT recommended by u-joint manufacturers is around 7 degrees and most installers shoot for around 2 to 3 degrees. The minimum sufficient operating angle for maximum joint life is about a 1/2 a degree. That's all the movement it takes to keep the bearings from brinnelling and ruining the joint. For that matter, the rear joint on a double cardan shaft MUST be intentionally set up with zero operating angle to eliminate vibration. The only time those joints operate under any angle at all is when the suspension flexes and they last just fine.

 

On the Mustang drag car we found a tenth with pinion angle. It likes about 6 degrees and the transmission is atabout 1 or 2 degrees. so I think that you may be on to something about the tightness of the clamps. They can really distort the caps it torqued to near failure of the fastners.

 

Check drive shaft balance.

Paul

 

The universal joints could be out of phase too. Line them up so they are in the same plane...eg if the U joint at the back is level make sure the front one is level too, or both vertical.

 

I have been told the same by a local Mustang racer as well. He is running 6 degrees down on the pinion, 2 degrees down on the transmission. The first thing I did was pull the drive shaft and had it balanced and checked for straightness. The weights are still on. Thanks.

Bernie

 

is yoke tight on pinion shaft? is pinion bearing and/or shims correct for rear? does u-joint fit correctly on both ends? unless you are beating the water out of it, you are either crushing the caps, (like all above posts say), or--something is walking under pressure in rear. vibration says movement. (bearing, yoke, shaft movement that appears at higher speeds) far stetched, but possible--are carrier bearings wearing out and causing drag?