Driveline Vibes @ 60+, Squatting Springs at Speed?

Just when I thought I put enough control arm shims in to get my front pinion angle right (after 1.5" coil-spacer lift), I start hearing a vibration at 60+ mph. I pull the front DS off and vibes go away. My pinion was 0.5° below by DS angle.

What makes sense for the Front? Searched and searched (lots of posts for the rear) and here is what I found:

- Front pinion should be just a hair above DS angle. (no reason given)
- Front pinion should be just a hair below DS angle, because the front axle is coasting most of the time (this makes no sense to me).

I agree with the first statement that I found, any one else agree?

- It makes sense that with an increase in speed, the more the front end gets pushed down from aerodynamic drag. Compressing the coils results in lowering the front pinion angle, which makes it worse in my case (or anybodys case).
- It also appears that the front DS is more fussy with vibrations as the Double Cardan angle gets larger.

On a link suspension, angles remain pretty stable,that being said the front CV will see about 2X the angle as a rear shaft.That really works them, so a good tight spline and centering ball are a must and are first to wear out.

yah try to keep that front pinion angle 0-2* below the ds angle. mine was 0* at pinion and 9* at ds angle with no vibes. now im around 9* ds and like 4* pinion with a lot of the slip showing and no vibes.

have you replaced the feront pinion u joint? probably the culprit.

blondejoncherokee said:

have you replaced the feront pinion u joint? probably the culprit.

Click to expand...

I had the Front DS rebuilt 10,000 miles ago, probably due for a check up (due to the increased angles). I don't think they went through the ball joint, just the u-joints and balance.

So is your front pinion pointed 4° up or down compared to the front DS? That seems like quite a bit and to not have any vibes...

Need to resurrect this old thread, I'm still battling this issue. Here is a recap:

My Rig:
- 1998 XJ Classic w/ 2" Lift (Coil Spacers in Front)
- Stock Front Driveshaft
- Stock D30 Front Axle & Gearing

Symptoms:
- "Droning" Noise above 60 mph (w/stock tires), gets worse the faster I go
- Don't feel any mechanical vibration
- All goes away when I remove front driveshaft

What I've done:
- Pinion Angle within 0.5° of Driveshaft, CV Angle ~8.0°
- Driveshaft - Replaced U-Joints/Balanced/Rebuilt CV Joint
- Replaced Ball Joints, Steering Knuckle U-Joints, Track Bar
- Replaced Front Output Yoke Bearing on T-Case

I do have a small amount of axial (in-out) play on my front T-Case Yoke, which I was hoping the new bearing would fix. I also measured the front driveshaft/pinion angles on my Brother's stock '96 XJ, and his pinion is ~4° up compared to the driveshaft, and he doesn't have any vibes, to this is counterintuitive to what the FSM says about driveshaft angles.

Here are my next steps:
- Install my Spare Front Driveshaft
- Eliminate Front T-Case Yoke Axial Play (Would I need to split the case?)
- Point Pinion Up

Only other thing I can think of is there is something fubar'd with my front diff/pinion. I only have 2" of lift, so I'd have to think I can get this fixed. Any advice would be greatly appreciated.

If you pull the front shaft and the vibes are gone then you know its the front shaft. Try grabbing the front shaft near the slip yoke and try shaking it, if you find play in the slip yoke that's where your vibes are coming from. Often times people never lube the slip yoke on the front shaft which causes it to wear out over time leading to play in the front shaft and vibes.

I would check all drives shafts and bearings and then pull the differential if you still can't find it. I know on mine there are some extra vibes and a low rumbling that fades in and out about once a second after 60MPH. The only thing I've found wrong is a worn carrier bearing. I'll be changing it after the holidays.

It may or may not be the issue, but you shouldn't have any play in the TC yoke.

I'd like to think so as well, but both of my transfer cases, 01 XJ NP 231 and 97 XJ NP 242, have some play in the front yolk. I know that in my 97 its because the front bearing moves slightly in the case. I figure it would either take bearing cement or a new front case half.