Is my driveshaft failing/out of balance?

Pablo94SC

Registered User
Long story short, car is smooth as silk until about 70mph. The vibration almost completely disappears at 85mph, only to return at 100mph and make the car feel like it's in a paint mixer.

Here's the troubleshooting list - New tires and wheels balanced/checked numerous times at 4 different shops. U-joints and half shafts are good. Bearings have no play and make no noise. Wheels rotated front/rear with no change. Vibration remains constant in all gears and while accelerating, decelerating, or braking. Only test I haven't done is swap wheels with another car to completely rule out a bent rim.

What do you guys think? Does it sound like the driveshaft is the problem?
 

91BLOWNBIRD

Registered User
I have the same problem right now 6mph-75mph then gone after yeah about 80mph then back at around 100mph...

In other words...yes, driveshaft.
 

the-big-e

Registered User
I would also suspect the drive shaft.....

With the age and abuse that these drive shafts take, it only has to get "tweaked" a little bit to cause a vibration....

Get the drive shaft balanced or replaced and your vibration should go away....

One other question: Has the trans ever been out of the car?
 

rlong

Registered User
i would check drive shaft bolts they have to be really tight , mine worked loose once and made a real fast vibration like you described other than that i would be looking at u joints for tight spots when rocking them back and forth or tranny mount or motor mount , or look at driveshaft for lost weights . ive never had bad ujoints yet i guess because the rear end is stationary so ujoints dont flex as much as in a solid rear end like the mustang , so im betting on loose driveshaft bolts

ralph
 
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RalphP

SCCoA Member
I'd do the U-joints in any case, if you've never done them.

Quoting from elsewhere:

Here is a Napa partnumber for the right one:
NPJ P354
Quote:
Contents : U-Joint and 4 external clips
Dimension : 1.06 x 1.06 Brg. Dia. x 3.62 x 3.62 Overall Width

The 3.22" joints are 1310 U-joints.
U-Joint Type : 4 Plain Bearings
__________________

Just so you know which ones to get.

It seems that it's recommended that you use the non-greasable ones for a stronger web.

RwP
 

kenewagner

Registered User
I would stick another set of wheels and tires on to try that. That is an easy way to check. I had that problem and it was out of balanced wheels. And they had been supposedly been balanced

Ken
 

Dirtyd0g

Registered User
I suspect wheels and wheel bearings first, but if you have a stock driveshaft you already know your driveshaft is junk. Crimped together driveshafts do not handle much abuse. I think it is the stupidest thing I have ever seen, shy of a rubber filled shaft.
Alan
 

Mike8675309

Registered User
When I had a balance issue with one of my rear wheels, it would vibrate at about 68mph and up to 75 (sucked on a road posted 70mph). At 80mph it was gone.

Next time you feel it, consider how it feels. Driveshaft vibration will be around the frequency of the transmission output shaft. Wheel vibration will be a lower frequency.
 

Pablo94SC

Registered User
Transmission has been out of the car (new - about 12k miles on it) and the rear pumpkin is a rebuilt one, not the original housing. I'll check the DS bolts to see if they have come loose, as this only became a noticeable problem about a month ago after an alignment (again done/checked 3-4 times). Before then, if there was a vibration, it wasn't significant enough to cause concern.

Thanks for the info on the U-joints. I wasn't sure what series they were. The stock ones are still in the car with about 180k miles on them, so is there any benefit to going to a stronger series, like 1350?

The only sound I get other than the rear view mirror rattling apart is a faint "woom woom" sound that's frequency slightly increases and decreases depending on the speed. Volume changes slightly as well based on throttle position, completely disappearing when I let off the throttle. I'm not sure what this is from, but given it's throttle dependence I've been guessing exhaust. I'm probably wrong though.

I still plan on doing a wheel swap before buying a new driveshaft. Here's hoping their wheels are balanced properly. LOL
 

rzimmerl

Registered User
I had almost the same sounds a couple years back, that I thought was wheel bearings. After replacing the bearings the sound was still there. It did not go away until I replaced the original drive shaft with the Mark 8 unit with new ujoints. Forward to today, after my trans swap the Mark shafts extra .4" of length finally would not let it fit, so I put the old stock shaft back in with the new ujoints and that sound is not there. My ruling was that the ujoints were causing my sounds.
 

Mike8675309

Registered User
Note.. our u-joints are 1330. They have the body of a 1350 joint, but the bearing cap of a 1310. Thus to go to 1350 joints you need new yokes to support the larger caps. Not sure if they are available for our application.
 

Pablo94SC

Registered User
It seems like there's a theme here of u-joints causing problems while still testing good. I may just have them replaced when I take the car back to the shop to have them tighten/clock the shaft to see if the vibration changes.

Note.. our u-joints are 1330. They have the body of a 1350 joint, but the bearing cap of a 1310. Thus to go to 1350 joints you need new yokes to support the larger caps. Not sure if they are available for our application.

So if I was to have a driveshaft made, then I'd have to make sure there is a yoke that will fit our application and accept 1350 u-joints. Did I get that right?

Another question - is aluminum worth the additional cost over a high quality steel driveshaft?
 
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Mike8675309

Registered User
Aluminum is lighter and due to that is taking less horsepower to turn vs a steel driveshaft. The downside to aluminum is they need to be physically bigger for the same strength of a steel unit, and their natural resonant frequency is at a lower RPM vs Steel. For some lengths the natural frequency can be in the rpm range that you drive.

Since the 1350 joints take larger caps, you will need to request a 1350 end yoke on the end of the shaft. You will also need a new flange that can support the 1350 to bolt up to the differential. Talk to a driveshaft shop and they can probably help you if you really want to do it. One thing to consider though, if a force occurs that would otherwise break a 1330 u-joint, and your bigger joint prevents the force from breaking the joint, what other part do you want that force to break? If the U-joint doesn't break, something else has to play the weakest link, and sometimes that something else isn't the cheapest thing to replace.
 

mywhite89

Registered User
Before you take the driveshaft out put the car up in the air and run it up to speed. I've seen driveshafts that shake like crazy up in the air. If it has a shake to it, its causing vibration. If thats the case, replace u-joints and have it balanced/checked. If its bent, replace it with an aluminum. The particular case I am referring to had a similar complaint as yours, it shook like crazy on the lift, new driveshaft.

Chris
 

92BirdFan

Registered User
I had a similiar problem on my 92 Sport. My vibration wasn't real bad but very anoying. I had the rear end gone through and the drive shaft re-balanced and nothing fixed it. Finally I replaced the front hubs and rotors when I was doing the breaks. I can't remember why I decided to change out the hubs but I did. After that the vibration was gone. I had done the rotors a couple time prior so I know it wasn't a rotor, it must have been one of the hubs. Hope this helps.
 
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Pablo94SC

Registered User
I'm trying to find a shop willing to take it up to speed while it's in the air. Wish me luck. This town sucks when it comes to finding a good mechanic. All the good shops here close down when the owners retire.
 

Raymondo

Registered User
I have been having a similar, if not the same, problem and was referred to Spencer Lee Transmissions in Horn Lake. As soon as I get through this Summer term I am going to take mine there.
 

Pablo94SC

Registered User
Update/fixed: Driveshaft's front u-joint was seized and causing all of the vibrations I was experiencing. Smooth sailing now.
 
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