help needed in Ft Worth

[buckethead]

I have been chasing a drivetrain vib in my xj. It started after I did the 4.56 gears. I started by removing the front driveshaft. With the front driveshaft removed the vib goes away. So I put new joints in it and had it balanced. It didn't help, when I put it back in the jeep the vibs come back. So I swaped the front and rear driveshaft, no change it still vids. Then I ran the front driveshaft in the rear with no front shaft and there is no vibs. I am not sure if its the driveshaft or something else. I would like to take a look at someone's XJ and and if possible put my front driveshaft in theres and see if it vibs or not. I have looked at the transmount, front yoke, and xfer case yoke. The only thing wrong is the xfer case yoke bearing is not as smooth as it could be, but it doesn't have any play in it. So I don't think its a problem. If there is anyone in the Ft Worth area that is willing to give me a hand that would be great. I will do the work and buy the beer.

 

[MischiefMan]

It doesn't sound like a shaft issue to me if it does the same thing when you switch the shafts.

When does it start to vibrate? Off idle? At 20? At 30?

Since it didn't begin until you changed gearing, I would start with that. Are you sure that your gears are set right? (not that I know anything about swapping gears...but I've heard that you have to make sure they are angled correctly)

 

[buckethead]

the vid starts at 65 mph. When you change from a 3.55 to a 4.56 the pinion speed in greatly increased. I would not have seen the pinion speed(front driveshaft speed) I get at 65 with a 4.56 gear untill 90 mph with a 3.55 gear. I never drove the jeep that fast so the problem may have been there before I changed the gears. I don't think its the front driveshaft either, I'm just trying to eliminate it completly before I spend any more money.

 

[MischiefMan]

Were any other changes made, or just the gears?

Did you install the gears or pay someone to do it?

 

[buckethead]

no other changes made. I had someone install the gears.

 

[MischiefMan]

Have you talked to the installer? I'd sure take it back to where the swap was done and have them check their work.

 

[Twisted_Dakota]

Have you talked to the installer? I'd sure take it back to where the swap was done and have them check their work.

X 2

 

[buckethead]

The front pinion is always turning weather the front driveshaft is in or out, if the front axle was the problem I should feel some sort of vibs with the shaft out. By taking out the front driveshaft all you eliminate is the xfer case and the driveshaft. It may be the front axle but I am trying to eliminate everything else before I take it back to the installer. Thats why I was wanting to put someones front driveshaft in mine and see if it changes anything.

 

[MischiefMan]

But if it behaves the same when you swapped the front DS and the back DS, it only stands to reason that it is not a DS issue.

With the front DS on the front, you said you had vibes. With the rear DS on the front, you said that you had vibes. With no DS at all, the vibes are gone. The link between the axle and TC must be the issue. From what you said, it doesn't matter what piece of metal that install between the two, you have the issue.

Nothing was changed with the TC, so the only logical conclusion, unless I've misread or missed something, is that the problem must be with the axle.

Now, I understand your logic that the 4.56 may be amplifying a pre-existing problem that you didn't notice with the 3.55 gears. The problem with this theory however is that it still involves the connection of the axle with the TC because all of the other components are still moving at the same rate of speed as they were with the 3.55's. You have said that you checked the TC, so that leaves the axle (although the bearing being "not as smooth as it could be" does provide a moment of pause).

Generally when people ask about front end vibes, my first question is: "Is it an up and down or side-to-side vibration?" Up and down generally means tire balance issues. Side-to-side indicates warn components such as ball joints. Of course, there is that pesky problem with the trac-bar not being tight and/or correct. These are all things that you would have noticed without the gear change though.

So, we're back to the TC or the axle.