Drive Shaft - Universal Joint - 420 SEL

[dproudfo]

Hey everyone,

I'm driving an '87 420 SEL and the car has been experiencing vibrations during acceleration for quite some time now. (over a year) The problem has continued to worsen so I've decided to address it. After inspecting the car it appears to be the universal joint at the center of the drive shaft that is loose and is in turn causing the vibration. The vibrations only occur through 1st and a little through 2nd gear so it's dependent on the load placed on the drive shaft. The sound is pretty much localized directly underneath the car so I've ruled out the rear axel.

My questions are

a) Does anyone know anyone that still machine's this part separately to avoid completely re-building the entire drive shaft? I remember buying the part many years back but am unable to re-locate where I got it from.

b) Any other speculations on the source of the problem?

Thanks again!!

(PS: The car has 280,000 miles on it)

[psfred]

That joint is straked in place, and you cannot replace it unless you have the proper jig AND a driveshaft balancing machine with the correct adapters to balance a Benz shaft (no one else uses the same ends).

The center rubber mount and bearing can go bad, and I'd check then and the joint, but if the joint is actually loose (that is, front and rear can turn a bit independently), I'd just find a used driveshaft. Should be $150 or so, not worth the effort to fix.

If not, they can be rebuilt, you will have to look around, but the last price I heard was $650.

to check a used shaft, remove the front half and turn the "stub" all the way out -- it must move in all directions smoothly, If it binds, it will vibrate.

Peter

[dproudfo]

Thanks for the feedback! I've been able to locate a rebuilt drive shaft for $300 shipped. Are there any other places I should look to try and find one for less?

thanks again!!

[harrywat]

where did you locate the rebuilt drive shaft? I need one for an 85 300DT.

Thanks

Harry