I think I have a bad U joint. The noise is a speed dependent sound like a bad snow tire that turns into a a grinding noise ask the car starts/stops. Anyway, should I plan on replacing all 3?

I see I can order scantech or GMB ones. The GMB has a grease fitting. is that a good thig? I normally steer clear of Scantech.

Thanks!
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Paul NW Indiana '89 740 Turbo 128,000

Have a driveline shop check the centre bearing as well as U-jts. The "snow tire" noise you report sounds to me more like a bearing than the U-jts. The usual clue to U-jt demise is driveline vibration and/or 'clinking' noises when changing from fwd to reverse or vice-versa.
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Bob (son's 81-244GL B21F/M46, dtr's 83-244DL B23F/M46, my 94-944 B230FD and 89 745 (LT-1 V8); hobbycar 77 MGB, and a few old motorcycles)

The noise turns from a howl to more of a grind as the car stops. Does the center bearing noise make a noie like that too? I'm considering replacing that too while I'm in there.
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Paul NW Indiana '89 740 Turbo 128,000

Grease fittings are a good thing. The original Ujoints have a set screws that can be removed and a 1/4 20 fitting can be installed. An occasional shot of grease from one of those disposable mini grease guns (limited space) should insure a lifetime of service. On the 740 cars a hole needs to be drilled in the plate blocking a straight shot at one of the fittings once installed; a step drill can be used with the plate still in place.

If I had to replace one Ujoint I would probably replace them all.

Be SURE that the segments of the driveshaft are reassembled with the same orientation to each other to help insure proper vibration free service. Mark them in some way (file marks, center punch dimples, etc)so there is no question. If you have the Ujoints installed at a shop be sure they understand this and check their work before you leave the shop when picking up the finished assembly.

Randy

I do this stuff for a living and honestly most the techs I know, myself included, don't even screw around with rebuilding drive shafts anymore. For a pretty reasonable fee I can have a driveline specialty shop replace the U-joints, carrier bearing, balance, and paint the damn thing and provide a warranty on their work. It is not worth my time to screw around with rebuilding them anymore. But, if you really, really want to do it yourself then yes, replace the center support and all three of the U-joints. I would use the GMBs or a set of Spicers if you can find them. Spicers are what came as OE in the 700 series cars. That compounded with the fact that the original patent that covered the basic U-joint as we know it today was originally held by Spicer back in the late 1800's. To say they know their stuff is a serious understatement. It is important to keep the unit timed up properly but I do not recall a 700 series driveshaft that you could assemble any other way, they have a "double tooth" set up where it splines together so you cannot put it back together any way other than correctly. Remember to order up the rubber support cage that goes around the center support bearing if you choose to do it yourself.

Mark

So I can just bring the driveshaft to an "driveline" shop and have them do the work? Do I still supply the parts or is that frowned upon? If I was going to do the center bearing, I was going to take it to a machine shop anyway. How much do they charge?

Also, is it wise to verify the culprit by raising the rear end on stands, putting the car in drive and listening for the sound underneath? I'd hate to do the work and find out it wasn't causing it.
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Paul NW Indiana '89 740 Turbo 128,000