Hi all:

I'm experiencing a low speed vibration with my rebuilt 1986 740 Turbo Wagon. I think it might have to do something with the Flexible Disc (#1 U-joint) and rear Motor Mount. The rear mount does appear to be soft and sagging. The Flex Disc has a little angular misalignment, between the Transmission Tailshft and the Jackshaft. It also has some small cracks in the rubber around the 3 bolts connecting it to the Jackshaft. With the car on stands, if I put the car in first and let it rotate. I notice some bouncing of the Transmission Tailshaft. I'm certain I need a rear Motor Mount. Do you think I need a new Flex disk with the cracks I described? This thing has a hefty price tag, $70.00 in my area. I'd rather not buy it if I don't need it. What else can cause this vibration? I read the FAQ's The shaft is aligned using the alignment marks.

Thanks
Warren

If the flex disc breaks the drive shaft drops to the ground and at 60 mph can cause a lot more damage then the 35-70 dollars, cheap insurance in my opinion.

No, it won't drop to the ground. One broke on the wife's car several years ago. I experienced some vibration from the drive shaft getting home, but it didn't, and can't, drop if installed properly with the proper parts.

There is a separate piece, which has a centering pin, that fits between the flex disc and transmission output flange. The pin fits in a recess in the front half of the drive shaft and keeps the assembly from going anywhere if the flex disc fails.

Thanks Guys:

I just ordered one from FCP Groton.

FCP Groton lists the flex disk on the 700/900 drivetrain page:

103-2223 Flex Disc fits all models that have one $32.00 Febi

I think the rear mounts go for $8 or so.

www.fcpgroton.com

Other places have similar deals online.
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Rob Bareiss, New London CT ::: '86 244DL- 215K, 87 244DL- 230K, 88 744GLE- 198K, 91 244 180K