Rubicon Express 3.5, advanced adapters SYE, Driveline Vibes

[98Redbird]

2001 Cherokee XJ with the LP Dana 30. RE 3.5" Super ride lift and 31's.

Advanced adapters SYE with tom woods' rear shaft.

Getting rhythmic vibes around 55 mph, and they progressively worsen thereafter.

I shimmed the rear with a 3° shim, and the vibrations stop when the front shaft is removed. So it's either in the shaft itself, or the angles.

Just had an alignment done and caster is within spec. Measured pinion angle/vs drive shaft angle, and they are 7-8° off... so, my understanding says, that difference will cause vibes? Is this a fair thought?

Just looking for help with solutions here? Multiple double cv shaft? Adjustable upper Control arms? Kit came with fixed lowers. Maybe just an old front driveshaft is the reason for the vibrations?

Thanks for the help

 

[Johnnie Walker]

Either swap in another driveshaft, or have yours balanced at a shop.

 

[Johnnie Walker]

But, sometimes you have to give up a couple degrees of caster for pinion angle.

 

[Tim_MN]

Reduce caster to increase pinion angle until vibes are: reduced/eliminated/acceptable. Consider swapping to a high pinion D30.

 

[md21722]

What front control arms are you using?

It sounds like you need front adjustable control arms to get the pinion angle closer to 1-2 degrees from the driveshaft.

I have also seen it where the rear driveshaft being out of balance tends to exacerbate a problem with the front.

I would not trust TW driveshafts for their balance.

Driveshafts spin fast and they can pick up harmonics from one another.

When the balance is really bad it can make your doors vibrate.

But with the 7-8 difference in the front I would start there first.

 

[CarbonXJ]

Reduce caster to increase pinion angle until vibes are: reduced/eliminated/acceptable. Consider swapping to a high pinion D30.

This. Get a good set of adjustable arms. I still have my LP D30 though and it's butter smooth, YMMV

 

[98Redbird]

Thanks for the responses.

Currently I am just using the kit LCA's that ship with the RE 3.5 lift. They are fixed.

If I do go down the route of adjustable control arms, since I already have the fixed lowers, should I just go with a set of adjustable uppers? If so which brand(s) is/are recommended?

Or since the RE lowers are longer than stock, would going with adjustable uppers be problematic? I'd be afraid of shoving the front axle too far forward.

Thanks

 

[trippled]

Before you go all out, have the drive shaft checked. If it's bad, you may be able to get it to an acceptable level with nothing else. I had loose splines causing exactly what you describe.