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[JMT]

I’d do it to see if it’s an issue with front, back or both. Then I’d address them as necessary.

Thanks for the advice.

I've read situations where the vibes only occurred when both drive shafts were attached. Remove one or the other and vibes went away. Not saying that is your situation, but that's what I did when I was diagnosing my vibes. I removed the front out of the equation. And just to make sure to myself, I also remove the rear shaft and ran in 4wd to verify. My vibes are coming from the rear shaft, or the combination of both shafts making the connection to the t-case. I have also entertained the idea of the t-case skid creating issues, which is why I went with a thicker Barnes skid. Adding a MML (Motor Mount Lift) netted the most positive change for my Jeep to date. As a last ditch effort, I'm trying one of Tom's drive shafts with the X spline design and triple checked balance.

Yeah, I've followed your case in a number of threads and re-read parts of it on Chris' thread addressing this specific issue yesterday. You're the outlier, of course. Maybe that X spline will help, that was one of @Alex01's suggestions that helped him get vibe free. Thanks also for the offer of the RS 55241's. I can't remember why you ditched those for something else, but I think I'm good now. At least my shock is still working. When I went into the muffler shop they asked me if someone had hit me from behind (when they saw it bashed into the shock body). I said no, of course, I would know that. Then it dawned on me that I had very likely backed into a large rock when wheelin Saturday and that pushed the whole exhaust forward, knocking it off the hangers and bashing it into the shock. What a day. With it chopped off I will never have that problem again.

 

[Alex01]

Since my TT in April, I'm getting those nasty harmonic oscillating vibes under load about 65mph+. 4.0, 6-speed, 456 gears, JB SSSYE, Adams DC

I need some help with the CA's front and rear. I'm trying to get the angles right so I can decide if I need to go to the next step and clean or replace u-joints (how do you know if those are bad), and finally have one or both shafts balanced.

Front pinion = 8.5*
Front DS = 8.3*
Rear pinion = 17.0*
Rear DS = 17.1*

I tried to start with everything even, and I've adjusted the rear several times up and down and didn't change a thing. The front I adjusted this morning. Pinion was 9.3 and DS was 8.4 or so and the vibes were coming on at 62mph, so it's a little better now that they are closer to even. What adjustments would you make?

I'd pull the front shaft and test for vibs. If the vibes are gone I'd send the front shaft back to Adams to get it rebalanced while stressing you need the tolerance levels tightened.

Your angles look fine.

*Just to note I had both the driveshaft rebalanced AND the X spline added at the same time so, I couldn't tell you if one or the other was the real problem. When @bobthetj03 gets an Xspline sometime in the future I'd bet we'll have a better understanding if it fixes the issue and is indeed a spline engagement issue.

 

[bobthetj03]

*Just to note I had both the driveshaft rebalanced AND the X spline added at the same time so, I couldn't tell you if one or the other was the real problem. When @bobthetj03 gets an Xspline sometime in the future I'd bet we'll have a better understanding if it fixes the issue and is indeed a spline engagement issue.

It will ship out Monday, so you'll know soon.

 

[Alex01]

It will ship out Monday, so you'll know soon.

Great timing.

 

[JMT]

I'd pull the front shaft and test for vibs. If the vibes are gone I'd send the front shaft back to Adams to get it rebalanced while stressing you need the tolerance levels tightened.

Your angles look fine.

*Just to note I had both the driveshaft rebalanced AND the X spline added at the same time so, I couldn't tell you if one or the other was the real problem. When @bobthetj03 gets an Xspline sometime in the future I'd bet we'll have a better understanding if it fixes the issue and is indeed a spline engagement issue.

My front shaft is OEM. Read that it’s not as robust and may need replace or better balancing to be up to the higher RPM’s.

Just took it out after about 5 more adjustments and the vibes don’t kick in till 68-69. Now I’m going to remove front driveshaft and see what happens. Just Take it off the pinion and tie it off somewhere?

 

[bobthetj03]

Wrap the ujoint caps so you don't lose em, then tie it off on the frame.

 

[JMT]

Wrap the ujoint caps so you don't lose em, then tie it off on the frame.

Looks like some grease has wept out of the unjoints. Do I need to remove caps and put some grease in there? Don’t want all those needle bearings falling out

 

[JMT]

Removed front DS, smooth as glass

 

[starkey480]

Removed front DS, smooth as glass

Knew it! Mine was exact same way. My dads same as well. He fixed his with a Tom woods driveshaft. That didn’t fix mine so I opted for the hub kit.

 

[JMT]

Knew it! Mine was exact same way. My dads same as well. He fixed his with a Tom woods driveshaft. That didn’t fix mine so I opted for the hub kit.

Hub Kit $$$$$$
Front DS $

 

[starkey480]

Hub Kit $$$$$$
Front DS $

I know I wish the driveshaft fixed mine for the cost savings. But I do like all my caster though

 

[bobthetj03]

Looks like you get to join the hub kit crew. That bites! You could try a new DS, but if that doesn't fix it, then it would just be an added expense, and you'd have to do hubs anyway. But, if it does fix it, then bonus. I'm not much help here, lol!

 

[JDS123]

If it is the stock driveshaft push up and down on the slip joint to check for play. Mine did that terribly.

 

[Alex01]

At 8.3 and 8.5 I have a hard time believing it's going to need a hub kit.

 

[Alex01]

I'm around 15 for the front DS and 9 at the pinion for comparison.

 

[JMT]

I'm around 15 for the front DS and 9 at the pinion for comparison.

Do you have it at 15 and 9 for caster?

If it is the stock driveshaft push up and down on the slip joint to check for play. Mine did that terribly.

Will check. Thank you.

Why did my vibes start after the TT, which is 2 years after my regear? The only thing that changed was the angle. Is it the oscillations at that steeper angle? Could I have hit the driveshaft and caused it to be out of balance? I don't see any damage visibly on the shaft? Can I have the stock shaft re-balanced by a shop?

 

[Alex01]

Do you have it at 15 and 9 for caster?

No. DS, 15, and pinion angle 9. I am not sure about caster since I haven't had it measured but it does return to center even with the psc ram.

 

[JMT]

No. DS, 15, and pinion angle 9. I am not sure about caster since I haven't had it measured but it does return to center even with the psc ram.

What I'm asking is why don't you have it more even, like 12 and 12?

 

[bobthetj03]

Mine is 7.6* pinion, 7.8* DS. My lift is about the same height as yours, but you have a tighter tummy than me. Mine is only a 1" tuck.

 

[Mike_H]

Before spending a bunch of money, take that front DS to a driveline shop and have it checked. Did you dent it last trip out?

Might be a simple as a bad ujoint. Look in the caps. If they are dry or have any powder in them, replace it. You might have a bad centering ball or slip joint too. Lots can wear out in the front d/s