One-Piece Aluminum Driveshaft Vibration

[Windy_3V]

Hey everyone,

I recently installed an FRPP one piece aluminum driveshaft in my ‘07 GT and I’ve been having some issues with vibration ever since. I know this is a fairly common issue but I wanted to get some opinions on where to look first.
Everybody seems to say something different but my car has a specific setup that I think is worth factoring into the equation.

So to start I have an entirely refreshed rear end in the car with less than 2,000 miles on it. It has Yukon 3.73 gears, Yukon 31-spline axles, and mechanical diff lockers all professionally installed. I also have adjustable sway bars, a pan hard bar, and BMR rear lower control arms on a relocation bracket.

There’s a slight vibration, almost pulsating mostly felt in 3rd and 4th gear above 3k rpm and gets faster as the rpm increases which isn’t that bad. However, at 90+ mph regardless of rpm or engine load the vibration is really bad. It’s super loud and pretty much shakes the whole car. It hasn’t really bothered me much when driving normally but the fact that I can’t get up to 100 smoothly kinda eats at me.

I’ve read that it could be a number of things like driveshaft imbalance, pinion angle, resonance, etc. But I wanted to get some input on where I should start before I go chasing the issue. Could the lower control arm relocation play a factor in the angle of the driveshaft? Should I just get the driveshaft balanced first? Should I get the whole drivetrain adjusted with all the new parts? Or could it just be the beefy rear end components and/or the driveshaft resonating at the wrong frequency.

Drivetrain components are one of my weak spots in terms of car knowledge so I don’t know too much about this subject. Any advice and info is appreciated and thanks in advance

 

[Gladams]

Try unbolting it and turn it and rebolt it in the new position. Try this (until you get back into the original position) and see if the vibration changes or goes away. If you have a lift, check pinion angle. Might help or might not. Good luck.

 

[86GT351]

What other mods are done to te car? Any suspenison work? First things that come to mind are Pinion Angle and unbolt the driveshaft from the Pinion Flange and rotate 180 degrees

 

[Laga]

FWIW, check to see if the CV joint articulates freely. I’m in process of replacing mine in a one piece aluminum DS from The Driveshaft Shop.

 

[GriffX]

I would start by measuring the pinion and transmission angle and adjusting it if not equal. To do this you need a 4 post lift (or ramps) and the motor/transmission mount must be ok.

 

[Hawgman]

Honestly, the first thing I would try would be put the stock driveshaft back in and see if you have the vibration.
May be the quickest way to determine if it is the driveshaft or something else, and eliminate a few frustrating steps

 

[stkjock]

Try unbolting it and turn it and rebolt it in the new position. Try this (until you get back into the original position) and see if the vibration changes or goes away. If you have a lift, check pinion angle. Might help or might not. Good luck.

Honestly, the first thing I would try would be put the stock driveshaft back in and see if you have the vibration.
May be the quickest way to determine if it is the driveshaft or something else, and eliminate a few frustrating steps

I'd suggest these in the above order, index the DS and see if the vibration is still there, if not swap back to the stock DS

 

[MasterofDisaster]

The manual for my 86 GT said to tighten a large hose clamp around the driveshaft and see if the vibration is better or worse. If it's not good, rotate the clamp 45º. Keep going until it's reduced or eliminated.

 

[brasil]

..MoD is right.. the hose clamp trick works good. And is also described in nearly all of the Manuals from Ford.