What is the difference between CV joints and universal joints?

 

Constant Velocity Joint: Double universal joint that cancels out vibrations caused by driving power being transmitted through an angle.
Universal Joint: A connection for transmitting power from a driving to a driven shaft through an angle.

[This message has been edited by r34 (edited 12-09-1999).]

 

Which ones are better? What are some advantages of both compared to the other?

 

Someone posted a truly excellent explanation of the difference between universal joints and CV joints on the Forum, explaining design, operation, and function of each.

I can't remember whether I'm talking new or old format; maybe someone remembers; if in the new format, the "Search" button may help you find it.

Tree Farmer

 

Maybe this will help you, Rooster:

Driving shafts and driven shafts used to transfer torque (transmission to differential/rear-end, differential/rear-end to wheel, etc.) in a vehicle’s drivetrain are typically aligned at an angle to each other rather than being linear. Moreover, their geometry is dynamic as the suspension moves up and down. To accommodate the angled drivelines, it is necessary to connect the shafts with some type of flexible coupling to “bend” the torque being transferred. Universal-joints and constant velocity (CV) joints both enable torque “bending”, but U-joints have severe limitations with large angles. When a U-joint is bent, two of the arms on the center cross (spider) travel in one elliptical path while the other two arms follow a different elliptical path. This causes a change in speed between the driving and driven shafts that results in vibration. The vibrations increase in amplitude as the angle increases – excessive angles lead to binding of the shafts as well.

CV joints handle joint angularity differently. One type of CV joint, used as an outboard joint, is designed so that when it bends, its steel ***** held in grooves or slots are positioned so that they always travel in a circular path exactly half way between the joint angle. This circular path is what ensures constant velocity by eliminating the cyclic variations in speed that a U-joint experiences when it operates at more than a few degrees off-center. Another type of CV joint, used as an inboard joint, is designed to move or plunge in and out to compensate for changes in driveshaft length that occur as the suspension moves up and down – something a U-joint can not do.

Thus, a CV joint performs essentially the same tasks as a U-joint, (and then some) yet better, and is designed to be totally maintenance free – provided it is properly sealed and remains that way.

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Greg McKinney


[This message has been edited by Texridr (edited 12-14-1999).]

 

OK, I looked at my brother's '99 Sportsman 500 and then my Uncle's '97Xplorer 500 in the back since they were side by side. The '99 Sportsman has the CV joints and the older ones have the universal joints in the back. It looks like the easiest way to tell them apart is the CV joints have the boot over the joint with the clamps and the universals are open with grease zerks. I don't see much of a difference with the angles, since they both have the same amount of suspension travel. The universals in the back have a boot over the middle of the shaft where it slides to compensate for the suspension going up and down. I also took Tree Farmer's advice and I found the older discussion of this topic and read some of the posts.

 

i dont like the stress that cv joints put on the rubber boot on 99 and up sportsmans. i think you will see these give more problems whith age.