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Discussion Starter #1
Can the u joint on the propeller shaft be changed. I find it hard to believe that it can not be changed. Some one has to have done it before. If anyone has any part # for the u joint that would be greatly appreciated. Hope you all can help. Dont want to spend a grand on new shaft. Thanks in advance
 

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Answer: probably, but it's not "official" or well documented. See how Blauparts has discontinued their replacement kits: Audi Driveshaft - Audi Driveshaft Repair Kits for Quattro's

The reality is that you can probably do it, but it may require some trial and error, and keeping your driveshaft out of the car longer than planned. I did this with a Mercedes, and it turned out fine. What was a big help was going to a local driveshaft shop where the owner quickly identified the correct replacement joint and gave me a few tips - he also would have done it for $85.

I think the issue on the 'W is that the u-joints are held in by the yoke being peened vs using snap rings. This means you'd have to "unpeen" to remove, and "repeen" or cut snap ring grooves. See this thread for some ideas: Drive Shaft U-Joint Is Staked/Crimped In Place, Now What To Do? - Page 2 - PeachParts Mercedes ShopForum
 

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It cannot be repaired because it doesn't exist.

There are CV joints at each end of the driveshaft instead of traditional u-joints. They are replaceable.

Are you talking about the carrier bearing, about halfway on the driveshaft?
 

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Why would there be a u-joint in the middle of a straight driveshaft that has CV joints on each end?? That's German engineering!
 

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I don't know, but as Scotts13 often points out, in a competitive market, they don't put expensive parts on for no good reason.
 

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Why would there be a u-joint in the middle of a straight driveshaft that has CV joints on each end?? That's German engineering!
And, there's a reason for it - shaft length.

Every rotating shaft (like, say, that center driveshaft) has what is called a 'critical speed.' Exceed that speed, and the shaft will hit resonance, and literally tear itself apart.
What determines the critical speed? Diameter, material, wall thickness (for hollow shafts), and (highly important) length. By effectively breaking the driveshaft into two parts, the critical speed (and, with it, the vehicle's top speed) is raised.

What happens when you exceed a driveshaft's critical speed? Go search YouTube for, say, "Mustang V6 drive shaft failure." Have a laugh at someone throwing a tune at a car (and, said tune removes the top-speed limiter that Ford put on those cars for a damned good reason), NOT upgrading the driveshaft, and driving it thru the failure. :lol:
 

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Discussion Starter #9
Thanks for all the input. I took the shaft out after work today. Gonna drop it at the machine shop that we use at work. See what they say. Get to rock a FWD for a bit i guess.
 

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With the open center diff (Torsen), you won't get far in fwd.

When dudes make their B5 A4s into RWD cars, they weld up the center diff.
 
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