QUESTION ON FLEX DISK CHANGE
 

I would like to change only the rear flex disk at this time. Can that be accomplished by removing the 6 bolts and exchanging disk. Or, must the center bearing mount be loosened or removed. Looked through a lot of threads, can't find the anwser.

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1984 MB 300SD Turbo

You will need to loosen the center carrier. 2 bolts no big deal.

IIRC, the rear shaft needs to be moved forward in order to clear the pinion seal at the differential end. To accomplish this you need to at least loosen the center support and the 46mm nut that connects the front n rear shafts.

If this does not do it, you'll need to drop both shafts.

No point in doing just one. The front one is usually the one that fails first. I'd do both if I were taking apart the whole assembly. Its not that hard. In fact I'd probably replace the carrier and bearing too....all inexpensive parts.

I second that thought! ;)

When should this be replaced?
 

Is there a consensus as to when flex discs should be replaced? typical mileage, etc? I don't believe, based on maintenance records that my wagon has had these replaced or even "looked" at...just something to add to the list I guess. :o

Visual inspection. FD will show obvious signs of wear.

1983 300 SD, about 360,000 miles. Original disks.

Mine didn't really show any signs of wear. I got motivated to replace them after seeing pictures of one that failed...basically turned the car into a throw-away.

Once I got the front and rear out (and center carrier) I could see small cracks forming on the inside web structure. Glad I did the job...really wasn't that hard.

From now on, I'll look onto replacing them at maybe 100,000-150,000.

There are different types of flex joints which look pretty much the same... be sure to check to see that you are installing the correct ones.... AND check to see if any TSB's have changed what is listed in the FSM for YOUR car....

How long they last probably depends on the environment as well as driving style and amount.....

In environments like MI they might wear out faster from the harsh elements (if driven in winter).....though in real dry/hot areas the rubber might dry out. It all depends I guess. I figure every 10 years/100k is probably more than enough.

where exactly is the front flex disc located? i climbed under there and found the rear one but if someone could tell me roughly where the front one is it could save me some writhing around under there.

Look at the tail end of your tranny and you will see it, It is what connects your tranny to your drive shaft.

I'm doing mine this weekend. I've never undid the 46mm nuts, and this will be my 4th one. What is the significance of undoing them?

I was looking over a lot of threads and have one other question. No problem taking the bearing off shaft. But, must universal joint be taken apart to use a press to install new bearing, or can it be pounded on with a sleeve and hammer?
Thanks all.

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1984 MB 300SD Turbo

No need to remove U-joint and should not be removed.

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