How do i?
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The actual viscous clutch assemblies are maintenance free. I have never heard of any going bad. If you have a problem with your diff. it is more likely a stretched chain or striped spines on the output shaft.
1989 325iX
1995 540i
1986 325eS R.I.P.
1984 325e R.I.P. -
they do go bad though. usually from abuse, such as running different tire sizes front to rear, or some other problem that causes there to be a large difference in rotational speeds between the front and rear wheels. what happens is the VC overheats, the housing cracks and the fluid inside leaks out.Originally posted by DanielHStout
there are a few ways you can test it that are fairly simple. the easiest and somewhat scary way is to put a jack under the front subframe (and on pavement!) until the front wheels are off the ground, start the car and put it in reverse. slowly let out the clutch (or brake, if you have an auto). if the car moves instantly, your VC is good. if you go nowhere, it's toast. don't try to move the car very far at all, if it starts to move right away then you have gone far enough. it can be dangerous to try and move your car with a jack holding up the front end!
the safer way, although it requires a little work (but not too bad) is to pull out the front driveshaft. you can then do the same test as above, only without having to move your car while a jack is underneath (which would be very bad if it happend to slip out or something while you moved forwards).
if you try the jack test, I wouldn't use a cheapie jack with one of those tiny jack pads. one of the larger jacks from say costco, harbor freight or sears should work well though.
another way to test, although not so accurate or easy, is to get the front wheels on pavement, and rears on gravel, and dump the clutch/floor it. you will still move forward, but with the front wheels getting power you shouldn't spin out very much on the gravel.
keep in mind that even if your VC is dead, power will still be distributed to all 4 wheels. the actual power distribution is handled by the planetary gear set (37f/63r); the VC only serves to limit the amount of slip between the front and rear wheels. in normal driving this is fine, but it can be scary on snow and ice.Comment
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im pretty sure the VC that controls the 4wd is good."front to back" I jacked up the diff and let the clutch out.... and it budged forward. later on while the car was in the air i spun 1 rear tire and the other side went the oppisite. i know its not a lsd... it has the VC in it. how do i check the VC in the rear diff. or do those usual never go bad?Comment
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im pretty sure the VC that controls the 4wd is good."front to back" I jacked up the diff and let the clutch out.... and it budged forward. later on while the car was in the air i spun 1 rear tire and the other side went the oppisite. i know its not a lsd... it has the VC in it. how do i check the VC in the rear diff. or do those usual never go bad?Comment
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the rear actually is an LSD, it's controlled by a VC as well. I don't know how to test it really. they can go bad though, the rear VC in my parts car was dead according to the guy I sold it to. :(Comment
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dang. i hope mine isnt. i dunno if both wheels turn the same whay since it uses a viscus insted of a clutch pack. I wonder if you can stick a normal 25% lock up diff in there. i dont think theres any in 3.93 though or whateverComment
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