55mph vibration

[russde]

OK, my '86 has developed (worsened really, it has been there for a while) a vibration that starts at about 50mph, grows worst at around 55-60 and then tapers off at 70.
While it was on a lift recently I noticed that the <vibration dampner?> at the front of the drive shaft appears to be shot, IOW the rubber is cracked and I can hold the outer portion while twisting the DS by hand and get quite a bit of movement.
Is this dampner necessary? Can it be removed? Would this require replacing the DS?
Thanks

[Eyelawdoc]

This is a common problem as our SVO's get older. Like Mike says, the easy fix is to swap in the Ford Motorsports aluminum replacement driveshaft. It fits and works just fine. I've got almost 20k on the one in my 84. Summit part # is FMS-M4602G, $159.95.

[KevinK]

I've had those vibrations 55-70 and it usually is the tires from sitting too long or just a plain bad tire. The vibration dampeners are there to do just that. You really need to find what is vibrating and then you won't need a dampener. The Ford manual is pretty good on this stuff.

[svobud]

Kevin .. I think the point the other two were making is .. it's probably the dampener that's causing the vibration in the first place ....

I would suspect .. if it's not the dampener, the it more than likely a u-joint. Either way, as suggested .. a FMS Alum D/S will cure both possibilities.

[gbeaird]

Russ,

If the damper moves like it is loose, you need to replace it NOW. If it moves like it is attached to a rubber bushing (you can move it and it springs back), you probably have time. The rubber will naturally crack with time.

Still, as all the others have said, get the FMS aluminum DS, if for nothing else than the performance gain due to the reduced rotating mass. Keep in mind, though, that the aluminum DS is NOT allowed in stock class Solo II competition, so you may get protested. The performance gain (something like 5-6 RWHP) is worth the move to ESP, IMHO. :-)

Gene Beaird
Still looking for an aluminum DS in a junkyard,
86 2R SVO
Pearland, Texas

[kennycoulter]

well, id say: its the wheel balance. if its at a speed, it is usually the wheels, bearings, etc. if it would be at ENGINE speed, i would say that a u-joint, balancer, etc. would be the problem. and when it deals with speed: low speed-usually bulge in tire or broken belt. high speed-bent rim, cheap tires, flat spots, weights fell off, weights shifted, etc. but thats all i really know. i worked in a tire shop for a while, and ate a lot.

[Felix Wankel]

Originally posted by kennycoulter
well, id say: its the wheel balance. if its at a speed, it is usually the wheels, bearings, etc. if it would be at ENGINE speed, i would say that a u-joint, balancer, etc. would be the problem. and when it deals with speed: low speed-usually bulge in tire or broken belt. high speed-bent rim, cheap tires, flat spots, weights fell off, weights shifted, etc. but thats all i really know. i worked in a tire shop for a while, and ate a lot.

the only vibration you get at engine speed is from the clutch, etc. , the driveshaft turns with the wheels.

[SVOeric]

humm
that is a great thought -- I have this clanking noise when running over bumps I've been trying to chase down for months --(more like years) --

I know you can change the yoke with another driveshaft that don't have the balancer on it --

[Dave W.]

bad vibrations

Russ,
My SVO has the same problem and it starts at about 45 - 50 MPH.
It didn't show up until I had the u-joints replaced and the drive-
shaft balanced. It gets worse until about 65 MPH and then subsides. The second harmonic of the vibration comes back at around 85 MPH and it's really bad. I'll be getting an Alum. DS as
well.

Good Luck !

Dave Warren
86 1C comp prep

[Eyelawdoc]

One of the appealing things about the FMS aluminum drive shaft is that it is very nicely made. You can even see the balance markings on it when you take it out of the box. In fact it looks so nice it is a shame that it's under the car where you can't see it

[kennycoulter]

yeah youre right, my other beater has a transaxle>>>>turns with engine rpm. my fault.

[Pat_in_L.A.]

You guys who don't have one, have NO IDEA what a difference the aluminum driveshaft makes. It is also less than 1/2 the price of all the other ones out there that are sold for other cars.

[kennycoulter]

is it the same as 5.0 driveshaft?

[Ken Potter]

Aluminum's great...

I too have aluminum drive shafts in both my Frankenstein car and the GT convert. I put it in "Frank" to gain HP and it made the most noticeable difference in smoothness on acceleration from a standing start. The convert was so bad it was about to shake the car apart. I also upgraded to an 8.8 in the convert while I was down there. Everything else I build will have aluminum from now on. Anybody want some free steel driveshafts?

[Otto Man]

This is Great!
I've had this bug for 2 years now and I just figured it would go away with the next set of tires. I was told Mr Tire has THE magic wheel balancer and to take her there and get everyone balanced again. Is that a waste of time? 160 for a new drive shaft is less then that stinkin horn pad!
One more question!
What besides the drive shaft do I/we need to pick-up before we crawl underneath? (U joints, etc)
Chris