Front Driveshaft vibes

I had front end alignment done and my front driveshaft was not instlled when I did this. Now after installing the front driveshaft I now get vibes that start about 60mph what do I do to correct this. I upper and lower adjustable control arms. This on a 98 XJ with Dana 30 4.56 gears and the RE 4 1/2" lift.

If your front end alignment was setup to favor castor angle vs pinion angle, then that could cause the vibes you speak of.

You could:

1) run without the front driveshaft

2) re-adjust the castor to get a better pinion angle

3) leave the alignment as is and get a hub-conversion kit

Before making any changes to your setup, however, I would check the front driveshaft for worn joints.

Lawn Cher' said:

If your front end alignment was setup to favor castor angle vs pinion angle, then that could cause the vibes you speak of.

You could:

1) run without the front driveshaft

2) re-adjust the castor to get a better pinion angle

3) leave the alignment as is and get a hub-conversion kit

Before making any changes to your setup, however, I would check the front driveshaft for worn joints.

Click to expand...

I have checked the joints they all seem to be fine. What should be pinion angle be with a 4 1/2" lift? Would I make my upper control artms longer or should I go shorter?

The pinion angle should be such that the driveshaft is inline with the pinion since there is a double-cardan joint at the T-case. Best determined with an agle finder. Install driveshaft, measure angles, and adjust accordingly.

Check the slip yoke for play. I just cured someones vibes when I found it was only this. Just push up on it and see if there is any movement.
Also to reduce your caster, lengthen the upper arms or shorten the lowers. What ever keeps the wheels centered in the arches. You can see my site on how to measure the caster but should around 5.5-6* at your height.

You wont be able to get perfect driveshaft angles, as pinion angle compromises castor!

Gojeep said:

Check the slip yoke for play. I just cured someones vibes when I found it was only this. Just push up on it and see if there is any movement.
Also to reduce your caster, lengthen the upper arms or shorten the lowers. What ever keeps the wheels centered in the arches. You can see my site on how to measure the caster but should around 5.5-6* at your height.

Click to expand...

So if I am reading your site correctly
I check caster by using a bevel square ( adjustable square ) with a level on it against the diff cover bolt heads that are above and below the axle or use the flat round area next to this. Then I set a protractor on the square and I should read 87.5 degrees correct?

Or I can put a protractor on the CV and see what my angle is once i get a reading there I minus 9 and that is what my castor angle is correct?

At 4.5", you want the angle to read about -86 degrees. As this is on the negative side as it should be, this will give you a caster angle of 5 degrees ( 9-4 degrees off vertical )

Gojeep said:

Check the slip yoke for play. I just cured someones vibes when I found it was only this. Just push up on it and see if there is any movement.

Click to expand...

I am having some vibes as well and have movement in the slip yoke. how did you correct this on yours.

Gojeep said:

At 4.5", you want the angle to read about -86 degrees. As this is on the negative side as it should be, this will give you a caster angle of 5 degrees ( 9-4 degrees off vertical )

Click to expand...

Stupid question but I want to make sure I am doing it right. I take the the bevel square and place it on my diff bolts top and bottom on the passenger side and them make sure the square is level horizontally and take the reading and it should read -86 degrees on the protractor.

Gojeep said:

Check the slip yoke for play. I just cured someones vibes when I found it was only this. Just push up on it and see if there is any movement.
Also to reduce your caster, lengthen the upper arms or shorten the lowers. What ever keeps the wheels centered in the arches. You can see my site on how to measure the caster but should around 5.5-6* at your height.

Click to expand...

Gojeep,

What did you replace? Why did the slip yoke have play?

Thanks,

The way to replace a slip yoke, without taking it to a drive shaft place, is to just pick up another whole shaft second-hand in good nick. I think it failed as he was running too much caster for the lift, still running stock caster at 5.5", and also lack of maintance. When I pulled the shaft the caps fell off and was completely rusty inside. He does a lot of mud running and just does not re-grease straight after.
The only thing I could use from the whole shaft was the top weld yoke and centre support in the double cardan for the rear shaft. He had a SYE with single uni's at each end which had already caused the flange yoke to wear letting the uni cups spin inside it from too much angle. So I had itconverted to a double cardan joint at the top from the old front shaft with new uni's fitted and the shaft shorten the length between the two uni's in the double cardan.