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U-joint question

U-joint question

U-joint question

With a larger U-joint will I be able to run it at a higher angle? Or with the larger joint comes a larger yoke and these cancel out any angle gains? This vehicle will not be run on the road so speed and vibration are not of great concern. I know the higher the angle the shorter the life, I have no problem doing the maintenance or buying a new joint once in a while. As long as the shaft doesn't bind, I'll be happy.

RE: U-joint question

A larger U-joint is stronger, so you may be able to run it at a higher angle, but I don't think so.  It's still spinning pretty fast.  When a driveshaft is straight, there is no rotation of the U-joints.  You may want to consider using a CV joint as they can tolerate higher angles.

RE: U-joint question


Hope this helps:
from a spicer chart

series  width  cap       max angle continous Short duration
                   Dia                             lb-ft         lb-ft
1310    3-7/32  1-1/16    30           130          800
1330    3-5/8   1-1/16    20            150          890
1350    3-5/8   1-3/16    20            210          1240
1410    4-3/16  1-3/16    37           250          1500


RE: U-joint question

"You may want to consider using a CV joint as they can tolerate higher angles."

The truck originally had a double cardigan joint, what you are calling a "CV" I had to take it out after the lift was installed. I got better results with a single u-joint at each end of the drive shaft.  The "CV" joint sticks out from the transfer case roughly 6" and the total length of the shaft is maybe 20". If I was going to use the "CV" I would have to cut and turn the knuckles on the axle, and thats not something I feel like tackling right now.

I'm not sure why, but the GM 1ton that I got the axle out of was not lifted and didn't use a "CV" joint either. Why was it used on 1/2tons??

RE: U-joint question

The reason for CV joints is to reduce the driveshaft acceleration and deceleration ramps.  During one complete rotation, assuming a less than perfectly straight in-line U-joint angularity, the driveshaft will encounter two distinct speed-up and slow down periods.  This rate of speed cycles increases with the square of the angularity.  CV joints maintain a somewhat stable driveshaft cyclic variation whereas a common U-joint does not.  The heavier the driveshaft, the more noticeable the forces.  This is what causes driveshaft sling at high speeds and torque loads.  Its not the size of the joint that allows for increased angles, but the clearances between the yoke surfaces in the driveshaft and input and output flanges.  The larger joints will allow more power throughput.

RE: U-joint question

I suspect the "CV" joint suggested above is the type used in front-wheel-drive vehicles.
It may not be easy to find in the sizes you would need, and replacing the stock cardan joints with the ball-knuckle fwd style joints could be a lot of work.
I suppose the type of u-joint selected would have a lot to do with the vehicle's sensitivity to any driveline torsional exitation, and how likely the occupants are to notice the results of it.

Jay Maechtlen

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