Back again with more questions -

I pulled the driveshaft last weekend and looking at the u-joint today I find that it seems to have a "detent" in the central position, i.e. it takes additional effort to deflect it away form center in all four directions. There doesn't appear to be any looseness or roughness, however, throughout the limits of travel. I have noticed a mild low frequency resonant drone at freeway speeds. Could this be due to the u-joint?

Though it's not normally a serviceable part I understand that some driveshaft shops can install a new u-joint in these and rebalance them. Can anyone recommend a place in the L.A area of So. Calif.? Otherwise, are there any recommendations for online suppliers? I've found a couple so far; Driveline Service or Portland rebuilds them with a greasable, replaceable u-joint, and I'm waiting to get a quote from them, as well as some information on lubing requirements and whether the new joint is staked or if they cut a circlip groove or something. They warranty for 5 yrs. or 50K mi.

The other one is Driveshaft Specialist, Inc. and they replace it using a sealed u-joint. They claim that the greasable ones require lubing every 5k mi. to get any useful life out of them which would be impractical on the MB. They have a good comparison of greased vs. sealed u-joints on this page. They warranty theirs for one year, but with unlimited mileage, and state that thier joints typically last upwards of 125k mi. Their price is US $329 - $374, incl. a new center bearing and carrier, UPS ground shipping and the $60 refundable core charge.

Does anyone have any direct experience with either of these firms, or opinions about greaseable vs. sealed u-joints?

Thanks

Gary