I recently made some inquiries with a company called Driveline Service of Portland, Oregon. about their rebuilt driveshafts, specifically for my 86 300E.

They replace the staked-in u-joint with a greasable, user replaceable u-joint. I asked them several questions about the process and the parts they use. I also asked them to give as detailed and technical an answer to my questions as they'd like and I would post their reply to this forum and others. I haven't yet decided whether or not I'll use their product, but I thought the idea interesting enough to put out there for others to consider or comment on.

Here's their reply:

"Greetings

Thanks for your inquiry about our remanufactured MBZ driveshafts. Answering your questions in order:

Lubrication intervals and recommended grease?
Given that the u-joints in a MBZ operate at a very low angle, and ours have a good quality seal and highly finished seal contact area, we suggest 25,000 mile lubrication intervals for maximum bearing life. We know from a few tests that sufficient lubricant remains after 50,000 miles of operation, so we erred on the safe side. A German spec for universal joint lubricants is DIN 51825-KP2, and specifically advises not to use grease containing molycote additives. Stateside, an EP NLGI Grade 2 grease is recommended. A specific brand that meets most manufacturers specifications is Chevron UltraDuty. The lubrication problem posed by a u-joint, is that unlike almost all other bearings which roll, a u-joint oscillates every revolution. This is notoriously hard on bearings.

What is typical life span of a u-joint?
The typical life of any bearing is dependent on a surprisingly large amount of variables. The 4 major ones that apply here are the load against it, (do you have a heavy foot?), the quality of the bearing, was it installed correctly and was it correctly maintained. Many bearings are essentially ruined upon installation. They must be fit in extremely specific and very tightly controlled spaces such that the rolling elements are not impinged, the rolling elements in this case being "needle bearings". Each needle bearing ideally carries its exact proportionate load, practically this is impossible, although in some extremely highly engineered u-joints intended for demanding industrial use it gets admirably close. Correct maintenance mostly is proper lubrication, which means the correct lubricant, correctly installed. Sounds easy, it isn't. A practical tip: do not grease bearings with the dirty tip of a grease gun through the dirty tip of a grease fitting. By "dirty", I mean any. Do grease a u-joint so slowly you are bored-with a hand gun, -no air operated. This way the grease will better flow to all four bearing cups.

The u-joint we install in our MBZ driveshafts has a calculated bearing life longer than the OE, due to a slightly larger contact area between the needle bearings and their raceways. OE joints often rack up 200,000 to 300,000 miles and still work. A reasonable conclusion is that since ours are engineered to last slightly longer that they last at least the same. We have yet to get one back with a known very high mileage, it will be very interesting when we do.

Our specs compared to the original MBZ design?
They are essentially the same in the dimensional control and quality of materials. What is different is that ours were designed to be replaced and lubricated.

Yokes machined or is joint staked in?
Our yokes are machined to accept a circlip, so it is user replaceable.

Greasable vs sealed? Sealed as an option?
We don't offer sealed joints as an option. With correct maintenance, a relubable bearing is superior. Note the word "correct". More and more, devices with sealed bearings are designed to fail about the time the whole thing is shot. This could be a good thing if a more organized and better controlled system of remanufacturing was in place.

If anyone wants additional information you may call me, Roger Vrilakas, at Driveline Service of Portland, phone 800 227 8608. Email is roger@driveshafts.com"

What do you think?

Gary