Vibration at highway speeds, what are the most likely culprits

[AKcharger]

Hi Guys

I got, a slight "rhythmic" vibration in the '70. It's really always been there but since I haven't drove it in 2 years I noticed it a bit more while driving it to/from Carlisle. It doesn't shake the car apart or anything serious, but after driving a brand new car it's noticeable. So here's the symptoms:

- Vibration starts around 40mph
- Noticeable "under power" when you let off the gas the vibration seems to go away
- U-joints are tight
- Lug nuts are tight

I'm thinking drive-shaft balance, what do you guys think?

[moparmoynihan]

It could be tire balance, a tire itself or an untrue rim.  A bent axle shaft would do it as well.  Just because the u-joint is tight does not mean its good. There could be rust in the caps or a needle bearing broken down that will cause a vibration.  Johnny 

[AKcharger]

Hmmm Good possibilities. Unfortunatly I forgot if I replaced the u-joints when I restored the car in '03  I'm thinking something in the drive train is #1 choice. Tires wheels possible especially since the car sits for a year at a time with only occasional moving back and forth by storage place. Don't want to think about an axle, plus how would you "bend" one?

Thx...any others?

[Just 6T9 CHGR]

My cyclic vibration looks like its in the rear itself.   Swapping in a friends spare 8¾ and matching driveshaft (small yoke) my vibration stopped.  Had my original driveshaft checked for balance etc & checked out perfectly.
My problem is a bad pinion bearing or a faulty set of gears (which I installed both myself about 10 years ago & pretty much had the vibration since then)
Rear is at a friends shop getting a new set of 3.55's and getting set up "correctly" this time

[Nacho-RT74]

I'm on a similar deal like you Chriss with a cyclic vibration( but starting at 100 MPH ) I had the same with my old open 3.23 741 axle small yoke, than with the new SG 3.55 489 axle big yoke

is somethin like RRRRRRRRRrrrrrrrrrrrrrrrrrrrrrrrRRRRRRRRRrrrrrrrrrrrrrrrrrrrrrrRRRRRRRRRrrrrrrrrrrrrrrrrrRRRRRRRRRRrrrrrrrrrrrrrrr

[Brass]

I think your initial guess is probably good, and the driveline is out of balance.  I had the same problem.  A surging vibration started up at around 65 mph.  Rebalancing fixed it.

[Nacho-RT74]

somebody told me about a posible worn tranny tailshaft housing bushings

[62 Max]

somebody told me about a posible worn tranny tailshaft housing bushings

First place I would check.

[AKcharger]

Tail shaft housing bushings??? you mean tail shaft bearings?   not sure what you mean by bushings

[Nacho-RT74]

dunno, I was told bushings... maybe they are bearings ? sorry, tranny is still something dark in my mechanic "knowledgement" LOL

[Just 6T9 CHGR]

Tail shaft housing bushings??? you mean tail shaft bearings?   not sure what you mean by bushings

There is a brass bushing in the trans tailshaft where the driveshaft yoke rides on.....some play in this area is normal.....more than you'd think..  I changed this bushing along with an NOS yoke & still have the vib....like I stated before mine was in my differential

[AKcharger]

copy all guys, will check

Thanks

[BrianShaughnessy]

Aluminum driveshafts work wonders 

[AKcharger]

really, is it because it's just new or is aluminium really superior?

[RallyeMike]

This type of vibration is not going to be a tailshaft bushing. The design of the output shaft and the yoke are so that when power is applied the splines lock up. The yoke does not ride on the bushing. The only time you will be damaging the bushing at cruise is if your driveshaft is so out of whack it vibrates enough to smack the bushing, and even then - it's not the bushing that will ever cause the vibration.

Always start with the easy (and free) stuff:

1. Swap tires with your other Charger.
2. Check your drive shaft angles.

Next...

3. Take the driveshaft down and have it balanced.

I would guess 95% of all vibrations are related to these items.

[AKcharger]

Me like um cheap way!

[Just 6T9 CHGR]

My cyclic vibration turned out to be my pinion bearing in my 8¾

[Rolling_Thunder]

are you running magnum 500s ?  if so that could be the culprit...   they are NOT hub centric and can be mounted slightly off-center. at least mine have before...     

[AKcharger]

I have rallye wheels. They balanced out OK but that's the 1st thing I'll swap out and see if there's a diffrence. Hmmmm Just thinking I wonder if a warped front drum could cause a vibration. I know I over heated the front right one once and had to have it reground

[NMike]

a warped drum will give you a brake pulsation. you'd feel it in the steering wheel, not hear it.

[b5blue]

Also try torquing the lug nuts to spec. with a torque wrench just like you would a head or other critical part. Some by me down here swear it makes a difference.