Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site lll-crg.ARpA Path: utzoo!linus!philabs!cmcl2!seismo!lll-crg!oneill From: oneill@lll-crg.ARpA (Neil J. O'Neill) Newsgroups: net.auto.tech Subject: Re: wheel bearings Message-ID: <974@lll-crg.ARpA> Date: Fri, 8-Nov-85 01:58:44 EST Article-I.D.: lll-crg.974 Posted: Fri Nov 8 01:58:44 1985 Date-Received: Sat, 9-Nov-85 05:47:37 EST References: <2427@sunybcs.UUCP> <204@ucdavis.UUCP> <2180@amdahl.UUCP> <114@emacs.UUCP> Distribution: net Organization: Lawrence Livermore Labs, CRG, Livermore Ca Lines: 42 Summary: what are CV joints > OK, what is the difference between a bearing an a CV joint. My > 1981 Dodge Omni, (yup readers, the same one) has "worn front CV > joints". On one of them (drivers side) the rubber bag that holds > the grease is ripped. The grease can disappear. ... CV or constant velocity joints serve the same purpose in a front wheel drive car that U-joints serve on a rear wheel drive car. That is, they allow a flexible connection between the transaxle ( or transmission) and the drive wheels. On a fwd car there is a CV joint at each end of each drive shaft. One connects to the transaxle and the other to the wheel. They are called constant velocity joints because they provide for the linear transfer of angular velocity through the joint. That is, if a shaft on one side if the CV joint is run at a constant 3000 RPM a wheel connected to the other side will run at a constant 3000 RPM regardless of the angle of the joint. If you run a constant 3000 RPM into a U-joint you will get an output that only averages 3000 RPM but actually speeds up and slows down during a single revolution (play with the U-joints in a socket-wrench set and you will see what I mean). This non-linear transfer of rotation depends on the angle of the U-joint. For a straight joint the effect is zero. And for the small angles encountered in rear wheel drive it is negligable. However, it cannot be neglected in the angles encountered in a fwd car. The angles are greater because the drive shafts are so much shorter and the wheels also have to turn to steer. So fwd cars use CV joints so that their drive trains don't self-destruct. The CV joints have ball-bearings inside of them, but these are not the front wheel bearings. The front wheel bearings are the ball|roller| taper bearings that allow the front wheels to spin smoothly inside the wheel housing. If the CV joint protective boot is cracked then grease can get out and water can get in and it would not be suprising if the joint wore out in short order. So called "split-boot" kits can be obtained which allow you to replace the boot without taking off the drive shaft -- the boot is split and you glue it back together after wraping it around the shaft. I have one of these on my Rabbit and it seems to be holding up. It is possible that your CV joints just need to be repacked with grease; you might want to ask your mechanic about this. oneill@lll-crg.arpa