12pack...its nothing in the front end. I get the vibration when I run the car up to speed on jackstands.

Gun. Axles are good. new 9'' currie with a dtroit locker. I had the rear shortened and axles shortened but it vibrated before doing that as well.

When I was under the car I banged around on the driveshaft and it wouldnt buge left right at all seemed good. Ill take the drums off and run it next. If there is still a vibration ill take the driveshaft in.

 

let us know what happens when you try it with the drums off

 

You should not be able to feel ANY motion through the joint.

 

Took the drums off today and vibrations were exactly the same. Took the driveshaft out to make sure it was not something in the tranny. It was smoth all the way past 4k. So I took the driveshaft in to inland driveline and they are going to check the balance.

Is the tailshaft of the tranny suppost to have play in it? Im talking about when the driveshaft is out

 

Running the trans with the DS out was probably not a good thing...but probably didnt hurt anything...Its bad because the DS is the final bearing for the tailshaft which is why it flops around like that.

-Gun

 

oh sure now you tell me..LOL

 

If it doesn't get better with rpm it's probably not the DS. Usually they will vibrate and then get better once it passes that frequency. Sounds like an axle to me. I'd check the run out.

 

Well while you are waiting for the DS To come back why not just for fun check for axle runout.

Take something with a sharp point and mount it securely to some type of thing that will hold it steady while elevating it to the mid point of the axle flange. For example big sewing needle that is c clamped perpendicular to a piece of 3/4" pipe and that pipe is clamped to a brick so it stays up... Simply adjust stuff until the point of the needle almost touches the edge of the axle flange...The needle tip will be pointing parallel with the car and just about touching the skinny edge of the axle flange. Simply rotate the axle by hand slowly and see if the distance between the tip of the needed and the axle flange changes. If you can see a change then the axle is bent...perhaps it was damaged during manufacturing. Also test on the axle flange face where the brake drum would mount.

Pretty much a free test...the car is already setup and it gives you something to do while you wait.

although with the vibration being the same with the drums off would appear to point to some other cause...most probable being the DS...unfortunately the low frequency vibration almost totally rules out a DS and screams axles.

I had a DS that had a worn slipyoke and it would begin to vibrate at about 70. A very high frequency vibration that you could not drive though as CPR mentioned. Not only could you not drive through it, it got exponentially worse and by 85 it was so sever that 90 was out of the question and I was like Holy Shiite! So this was a case of a DS issue secondary to slipyoke that you could NOT drive through.

 

Ill check runout tomorrow morning. Is it possible I could of over-tightened something when installing the axles?

 

The bearings are good right when you force up and down on the axle you dont feel any play right?

If it really does have run out chances are it came that way new...But then again that 347 aint no joke is it?