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Discussion Starter #1
I just recently purchased a '84 300D and everything was going great until the driveshaft center support bearing broke. Fortunately it happened within 2 miles of home and I was able to make it without tearing the car apart.

Is there anything special about raising and supporting the rear end on the 300D? I have the front on ramps and was about to lift the rear by the differential when I noticed that the rear suspension and drive line is like nothing I have ever worked on.

Also, any pointers on replacing the center bearing support would help. I do have the Haynes manual, but I have found those to be less that stellar at times.

I'm also planning on just replacing both of the flex discs while I have it apart.

Thanks, Rhuprect (the monkeydog)
 

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'81 300TD Turbo
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Not much special about raising the rear, but if the jack points are still stable, use those. If you are using ramps for the back wheels also, keep the jack handy because you will need to spin a wheel at some point during the project.

When I changed my center bearing it was quite a bear, mainly because it either had not been changed in quite some time, or never had been changed. Things were a bit frozen.

You'll need to remove the transmission mount and block the transmission up. I let mine drop 3 or 4 inches and supported it there. You'll need to let it drop some because there isn't enough movement of the forward shaft over the rear splined section to get the centering bushings clear on either end. I ended up prying mine a little to get past the flex discs. Don't know if this will be easier if you're removing the discs also. While you have it out, change the centering bushings on each end also, as you won't want to have to remove the shaft to change them later.

The centering bushings were the hardest part of the whole thing. The manual says to drill a hold through them and pry them out by putting a bar through the hole. Personally, I think this is total BS, as there is no way in hell those things are coming out of there using this method. I ended up tearing the center out of the bushings and carefully splitting them with a Sawzall. Then I used a punch to push one side in toward the center to get them to loosen up.

Putting the new bushings back in is also somewhat of an exercise in patience, as they do not want to go into the hole (they look to me like they are press fitted). Eventually I got them lined up and drove them in with a mallet and block of wood. I'm thinking that putting the bushings in the freezer the day before and then heating the yoke up a little just before putting the bushings in might make things a bit easier.

Most important is to mark the front and back shafts so that you get them lined back up the way they were before pulling them apart. I took the front and back shafts out of the car without separating them and then using a laser level, projected a line down the center of the shafts and used a paint marker to paint a line along the laser line.

To do the whole thing, you'll need:

2 Centering bushings
2 Flex Discs w/bolts
1 Boot
1 Center Bearing
1 Center Bearing Support
1 Transmission Mount (if your's is toast)

If you change the transmission mount, you will probably end up with the later style that doesn't have the limiter on it. Technically, you should get the rubber bumpers that were used with the new style mount that keeps the tranmission from bumping the tunnel, but I didn't put them in mine and have had no problems. That's just me though.

Also do yourself a favor and visit the MB dealer and get the 4 blind nuts and bolts for the transmission mount bracket. Two of mine broke when removing them and I didn't have replacements. It was going to take too long from MB, so I ended up using some standard thread blind nuts and bolts I found at Home Depot. Not quite what I wanted, but just as strong. Someday I'll get the correct ones for it.

You'll also need to find a big crow's foot or something similar to loosen and tighten the big nut on the shaft. I used two pipe wrenchs (who needs a torque wrench when you have calibrated arms). A torch is also quite helpful.

Oh yea, and the MOST important thing... Adult beverages. If you don't drink, drugs. If you don't drink or do drugs, some nice classical music to calm the soul. All three might be good too. You will at some point probably want to throw something if you don't get a handle on the stress factor early in the game.
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Discussion Starter #3
Thanks for the mechanical advice. I just ordered the parts.

As for the stress factor, I have that beat. Whenever I work on my car, I sell tickets to the general public and bill it as a swearing class. My guarantee is that even an ex-Marine will learn at least two new cuss words. The stress is relieved when I realize that I have made enough money off my students that I can throw the whole mess on a tow truck and send it to someone that knows what the hell they're doing.

If the profit from the classes falls short of the cost of repair, it all goes towards the booze and the drugs.
[:D]
 

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Well, I finally crawled under there and started tearing the driveshaft out. Someone has recently replaced the flex discs so the bolts are all cooperating. Now I’m sorry I spent the $80.00 on the discs, but it’s worth it to have all the bolts unfrozen.

Just a couple more questions:

Should I be able to remove the driveshaft without removing the exhaust? The Haynes says nothing about the exhaust, but it’s not there in the pictures. It looks like I should be able to feed the shaft out the back with the exhaust still there.

Will just removing the rear transmission mount work or do I have to loosen something else up by the motor?

Thanks again for the help.

Rhuprect
 
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