Driveline vibration

[Calgary351GT]

I'm sure this is a thread that has already been covered at some point but...

A few months ago, I installed a set of lower trailing arms in my 90 GT, after which, I discovered a vibration through my shifter at about 60mph, especially under exceleration. I had no vibration before the change.

I was told I had probably altered my pinion angle, therefore I installed a set of adjustable uppers.

I've since corrected the angle.
Although the vibration has reduced a bit, it is now more severe at 70mph+, regardless of exceleration or deceleration.

It sounds like my driveshaft is out of balance, but it was fine before the trailing arms were installed.

I've heard the new urethane bushings could magnify a driveshaft balance issue otherwise disguised(dampened) by the soft, stock rubber Ford bushings. That sounds like a bit of a stretch to me.

Has anyone experienced this problem or have any input?

 

[2000xp8]

The control arm setup may of magnified an existing problem.
Usual culprit in this case is the driveshaft.
I'd get a FMS aluminum driveshaft.

 

[Calgary351GT]

The control arm setup may of magnified an existing problem.
Usual culprit in this case is the driveshaft.
I'd get a FMS aluminum driveshaft.

That's the one I have my eye on, already priced it out.

 

[97gsr]

i have the same exact problem but mine happened when i switched to the stiffer engine and trans mount. instaled new U-joints on the d-shaft but the problem still exists so if that fixes yours i will try it also.

 

[SPEEDYLIFSAVR]

just for kicks , check your balancer.....could be coincidental .

good luck!

 

[2000xp8]

Balancer would do it without the car in motion.

 

[SPEEDYLIFSAVR]

true.....but with the increase in rpm's the vibration would become more noticeable .

 

[Calgary351GT]

Thing is, there was no vibration until I change out the lower trailing arms.

 

[97gsr]

were your old bushings wore out on the LCA's? if so that could be where the vibration was going. now since you switched you noice it more.

 

[1Slow90coupe]

I am having the same exact problem....I have stock uppers with poly bushings, MMS lowers, poly trans mount, and new FMS aluminum driveshaft that was changed to try and fix the vibration. Mine starts at 75mph and get progressively worse with higher speed........

 

[93 LX]

if you removed the drive shaft then you may have clocked it. try rotating it 90 degrees at a time until you either get rid of the shake or you get it back to where you started...

 

[Calgary351GT]

if you removed the drive shaft then you may have clocked it. try rotating it 90 degrees at a time until you either get rid of the shake or you get it back to where you started...

I thought of doing that only after I started installing my new FMS aluminum driveshaft tonight.

Hope that wouldn't have worked....

Anyway, the new driveshaft did the trick. I have a small amount of vibration under heavy acceleration. I'll probably turn down the pinion a degree or two to take care of that.

 

[2000xp8]

The FMS aluminum DS is a good investment anyway, at least if you had to spend money you got something worth it.

 

[Jmunk]

How are your U-joints. Like the others said a aluminum DS is a good investment.