Have tried every possible thing that I can do.

91’ XJ, 4.0 Litre, Dana 44 rear diff, 3” lift.

Vibrates @ 35 MPh plus.

1*, 3*, 4*, 5*, and 7* shims.

In the current iteration 6* shims. 13.6* angle on the propeller shaft. 13.8* on the pinion angle.

Backing down to a 5* shim made the vibes much worse.

Three different Tom Woods drive shafts.

Now an Adams drive shaft.

On the third t-transfer case.

Second transmission.

Pull the rear drive shaft, drive around, it’s all good, no vibes.

Is the goal of shops to f* stuff up?! In this latest episode, cannot get into 4WD despite the Novak shift cable. I will figure that out.

Feel like I am trying to win the lottery.

 

Do you a SYE now ?

 

Per tech's comment above....you're not clear if you have a Slip yoke eliminator. Your angles should be perfect to not have vibrations if you have the stock slip yoke style shaft. If you do have a SYE...your angles are off. You want the pinion in direct alignment with your driveshaft. Don't mean to tell you what you already know...it's just not clear what you've got right now.


My suspicion is you do have a SYE kit as you've bought new driveshafts....not many spend money on a new stock style driveshaft. You just need to fix your angles to the above sketch. This makes more sense to me for the vibrations to happen at a higher speed.

If you DO NOT yet have a SYE...My initial thought is that 3" might have given you more than 3", and the driveshaft is binding at all times...only becoming apparent when it's spinning that fast.

2 options in my mind in that case:
1) Get a t-case drop. This would help prove if it's a binding issue. This is only for a test, I'd never recommend a t-case drop to leave in.
2) Just go for a SYE. You've already got all the shims you could possibly need to get the angles correct for the double cardan joint driveshaft.

Let us know what ends up working!

-Nick

 

Just curious, with a SYE, DC shaft, and the pinion turned up towards the sky,,, How does one lubricate the pinion bearing?? especially the outer bearing.
It would not be a problem with a trailered off road rig,, But if it is a DD or an "overlanding" rig,, that outer pinion bearing will burn up eventually

 

My drive shaft is like 2nd one and it run smooth and have no problems with lub getting to the pinon bearings .

 

So long as your pinion has an oil slinger and that slinger hits the lubrication, there should be no problem with lubrication with the mild angle. When you tilt the pinion too far (mostly in shorter wheelbase vehicles), relocating the fill plug on the cover is a decent idea.

 

If you think about what is going on in side the rear end when your going down the road you wouldent worry about bearings not getting oil , the oil doesn't just set there .