New aluminum driveshaft or rebalance stock

[marcoc]

My 99 has 4.10's and at speeds over 70mph I have a vibration that gets slightly worse as speed increases. I have read that this vibe is common with taller gear swaps. Aluminum DS are suppose to reduce the vibes and American Muscle has one on sale now. Are these vibes causing long term damage? The car is not daily driven maybe one a week. Mods on my Cobra are on my signature. Would rebalancing my stock steel DS by a reputable driveshaft shop help with reducing vibes? They would also install new u- joints all done for about $100.

 

[1999marg]

If you did not have a vibration before the gear swap and you did not drop or bang the driveshaft taking it out try simply indexing it. You should be fine. If that does not work have a driveshaft shop check your steel shaft just to be sure.

Good luck
Mike

 

[pdm]

Mine vibrates from too shallow of a pinion angle which is almost impossible to get with the irs

 

[marcoc]

Car had gears installed before I owned it.
It always had the vibe even on the test drive. It's not a crazy vibe but it's there. Had the rear diff. Rebuilt last year so that is good. I have had vehicles with drive line vibes before, it's gotta be the drive shaft. Universal joints are fine checked them. I made up my mind and just ordered the aluminum drive shaft from American Muscle, it was on clearance plus two discount codes got a great deal that that i could not pass up

 

[marcoc]

Spoke with a local driveshaft shop about it today and they are associating the rotation of the shaft due to the higher gear ratio causing the vibe. He told me at the price American Muscle was selling the aluminum driveshaft he couldn't even come close by $100.

 

[R.D.P.]

Car had gears installed before I owned it.
It always had the vibe even on the test drive. It's not a crazy vibe but it's there. Had the rear diff. Rebuilt last year so that is good. I have had vehicles with drive line vibes before, it's gotta be the drive shaft. Universal joints are fine checked them. I made up my mind and just ordered the aluminum drive shaft from American Muscle, it was on clearance plus two discount codes got a great deal that that i could not pass up

Good luck, let us know how it works out for you when you get it installed.

 

[marcoc]

Will do. I did extensive reading on others with vibes after higher gear installs and the aluminum driveshafts have aided in reducing vibes and some even have gotten rid of them. Hopefully this helps my high speed vibe. Atleast i will have less rotational mass which will help with the signature drivetrain "play" on our cars and increased throttle reponse.

 

[01yellercobra]

I have the aluminum d/s out of an 03 Cobra and when I went to the 3.90's I developed a vibration around 70mph. I reclocked it 180 degrees and the vibration moved up to 90mph. I think I'm going to get it balanced.

 

[marcoc]

I have the aluminum d/s out of an 03 Cobra and when I went to the 3.90's I developed a vibration around 70mph. I reclocked it 180 degrees and the vibration moved up to 90mph. I think I'm going to get it balanced.

This may be a dumb question but are factory driveshafts balanced from the factory before they install them in a car on the assembly line? your 03 DS is technically a stock piece. my vibe started at 70 mph and gets worse as speed increases. Hoping the aluminum shaft helps with no vibes

 

[01yellercobra]

This may be a dumb question but are factory driveshafts balanced from the factory before they install them in a car on the assembly line? your 03 DS is technically a stock piece. my vibe started at 70 mph and gets worse as speed increases. Hoping the aluminum shaft helps with no vibes

I would think so. But I imagine there's a limit they're balanced to. And the 3.90's take it past that limit. I never had an issue with the 3.27's.

 

[shurur]

DS length for '99 with T45 and IRS is 44.5"
Your new 45.5" DS will be tight..see how it goes.

T45/3650 to IRS ('99-01 Cobra) has this odd length..
I bought a P71 DS off ebay and had it cut..

 

[marcoc]

DS length for '99 with T45 and IRS is 44.5"
Your new 45.5" DS will be tight..see how it goes.

T45/3650 to IRS ('99-01 Cobra) has this odd length..
I bought a P71 DS off ebay and had it cut..

I bought the one off American Muscle. They state its specific for the 99-01 cobra. According to the comments no one complained about fitment. Also spoke to a driveshaft shop again and they told me the stick shafts are not balanced as well as aftermarket aluminum shafts. Plus the aluminum handles higher rotations much better and they balance easier.

 

[marcoc]

Right from their website:

PRODUCT FEATURES
Quicker acceleration
More responsive engine
Seamless 1-piece aluminum tubing
Made in the USA
31 spline design
44.5" length shaft
Includes new pinion flange
Fits manual 1999, 2001 SVT Cobra Mustangs

 

[quick01snake]

DS length for '99 with T45 and IRS is 44.5"
Your new 45.5" DS will be tight..see how it goes.

T45/3650 to IRS ('99-01 Cobra) has this odd length..
I bought a P71 DS off ebay and had it cut..

If you're referring to the FRPP J shaft above, that's what I ran on my 01 for some time. It was a tighter fit than the stock length but never had any issues. It also cured my 70+ vibe, but upon further inspection of the stock one, the u-joint cup bores on the front of the shaft were worn, causing slop and most likely was the source of my vibe. New u-joints did not help it much if at all.

Hope this helps some

Currently looking for a deal on a used one-piece aluminum ds for my new stang

 

[shurur]

Right from their website:

PRODUCT FEATURES
Quicker acceleration
More responsive engine
Seamless 1-piece aluminum tubing
Made in the USA
31 spline design
44.5" length shaft
Includes new pinion flange
Fits manual 1999, 2001 SVT Cobra Mustangs

Ok..I see AM is selling something new and the right length (44.5")...good..

 

[shurur]

If you're referring to the FRPP J shaft above, that's what I ran on my 01 for some time. It was a tighter fit than the stock length but never had any issues. It also cured my 70+ vibe, but upon further inspection of the stock one, the u-joint cup bores on the front of the shaft were worn, causing slop and most likely was the source of my vibe. New u-joints did not help it much if at all.

Hope this helps some

Currently looking for a deal on a used one-piece aluminum ds for my new stang

Yah..I see the P71 Crown vic AL DS has dried up....may be getting bought up by insiders or eliminated some other way....so much for getting some of our tax dollars back...

 

[marcoc]

I didn't want to screw around with the Ford Racing driveshaft so found the American Muscle one that looks like a direct fit

 

[1999marg]

Just out of curiosity does your car have the factory front diff brace or was it retrofit with an 03/04 front diff brace? My 99 vibrated at 75 plus with the 03/04 brace. I have 410's too and the car has zero driveline issues with the stock brace. I noticed a slight alignment issue when I first installed it. Against better judgement I put it on and well you can guess the rest. Mitchell Differential in Mass is a great source for diff and driveshaft work.

You should check your driveshaft, transmission/engine, and diff pinion face angles to make sure everything is ok. Let me know if you need a link on how to do this correctly. It is a snap if you use the angle finder app in your iPhone. This step is often overlooked. A major benefit of an IRS is a smooth driveline.

Good luck

 

[marcoc]

I have yet to install the diff brace. I actually purchased it from a member used and in great shape. It came off an 04 Cobra I belive. Also I need to install the Aluminum DS, it has not arrived yet. My steel DS was in good shape as far as ujoints but balance I am not sure about. My car has chopped oem coils right now but Steeda springs are going in in a few weeks. the car is lowered about 2-2.25" on the current chopped coils. the vibe always was there even the day I bought the car again only above 70mph. I hope the DS helps the vibe. The brace is to compliment the rear IRS repairs I did last winter to help prevent wheel hop.

 

[marcoc]

Just out of curiosity does your car have the factory front diff brace or was it retrofit with an 03/04 front diff brace? My 99 vibrated at 75 plus with the 03/04 brace. I have 410's too and the car has zero driveline issues with the stock brace. I noticed a slight alignment issue when I first installed it. Against better judgement I put it on and well you can guess the rest. Mitchell Differential in Mass is a great source for diff and driveshaft work.

You should check your driveshaft, transmission/engine, and diff pinion face angles to make sure everything is ok. Let me know if you need a link on how to do this correctly. It is a snap if you use the angle finder app in your iPhone. This step is often overlooked. A major benefit of an IRS is a smooth driveline.

Good luck

Link would be great, thank you.