Yesterday I install the Coast 1310 front drive shaft on my 3.5" lifted jeep (auto). I took it out for test run and never got any vibrations, most likely due to me driving in the neighborhood under 30 MPH.

This morning on my way to work when I hit 40+ MPH I started to get this crazy vibration that I could feel in the seat and arm rest. Also, it seems like I was getting a "humming" like sound - other than my tires.

I brought it into the shop this morning to check my caster/pinion angle and everything seems to be in specs. Any ideas? Maybe warped drive shaft?

 

i couldn't read your caster numbers but, assuming they are within factory settings, could be the shaft is out of balance. i doubt it but, it can happen. can you please post up what your caster is set at? too much and that would explain things

 

What is the Pinion angle? Seems they didn't spec out your caster either.

 

Double cardan joint at the t-case?
What's the angle between the front pinion and the drive shaft? More than a few degrees?
How is the drive shaft connected to the t-case? Is there an extension, or is the yoke close to the case?

Stay below vibration speed until you get it figured out.

edit to add:

Why did the caster get left out?

I noticed it says individual toe can't be adjusted. That's strange, because it can be adjusted individually.

 

Yes - double cardan joint at the t-case.

Not sure on the angles. I didn't measure last night because I didn't know that it was wack until this morning. I will have to check when I get home. What angle should I be at between the pinion and drive shaft?

I checked the sheet they gave me and the "Caster" is greyed out like they didn't measure it. What angle should that be? I just got off the phone with the shop and he told me that it was greyed out because it is not adjustable... don't know?

I asked him if he could hook it back up to the comptuer to at least give me a angle reading. Going at lunch and will post up the Caster angle numbers afterwards.

Thanks guys for the help. I have a pre-jeep jamboree run this Sunday and have some family coming out of town to ride.

 

Forgot to answer. There is NO extension, there is a yoke on both sides.

 

I went back to the shop and my caster is set to 5.7.

I asked the guy to adjust my control arms and they told me that they didn't know how to do it. Go figure. So I looked under while they had it on the lift and one of my control arms is as short as it gets. I guess I have to buy some LCA before my ride this weekend to adjust the caster.

I am leaving work early to take it to the 4x4 shop to see what they can do for me. Also, David at Northridge has been helping me also via email - koodos to him.

 

Wait, what ca's do you have now?

 

You have a RE lift with fixed lowers and adj uppers?

Lengthening the uppers will lower caster and raise the pinion, which should lessen the driveshaft vibes.


This writeup will show you how to adjust them.
http://project-jk.com/jeep-jk-write-...-end-alignment

 

I have RE upper adjustable. When I looked underneath the jeep one of them is shorter than the other, not sure why though.