About ready to give up- Front DS vibes, 01 xj- Advice appreciated

[srmitchell]

All the yokes are completely tight. (I should probably double check the front one again though.)

 

[lazyxj]

I've had a hub kit on mine along with 4340 inners and while it was a lot of money, it really made driving it on the street a pleasure. No vibration no noise.
For Sean and mako my day, I certainly would not give up or sell the rig. I would get a hub kit any day before doing that.

I think Eric has the solution to a problem that has no simple fix. The front CV joint is spinning too fast with 4.56 gears

I have battled the same front shaft vibration and have concluded the CV-joint has too much angle to spin much over 2000 RPM without severely vibrating. On my 2001 XJ, the rear CV joint bends about 6 degrees while the front bends 15 degrees, That's 7.5 degrees per u-joint which is way too much for highway driving. With the front of the transfercase pointed upward several degrees, there is no way to reduce the front CV joint's operating angle, beside lowing the lift. Trasfercase drops, instead of SYE conversion, will aggravate the situation.
Google seaches shows the the front shaft problem to be fairly widespread on lifted XJs.

I have tried all the standard fixes, re-ballanced shaft, new shafts, new transfer case, setting and re-setting the u-joint and pinion angles, all without much success. Only thing that cures it is removing the front shaft, which also requires removing the transfercase's skid plate, something I'm not too interested in doing after a long day off-roading.
I shot some hi-speed video of front shaft spinning, while on jacks stands and you can see the front CV joint bouncing as the RPM approach and exceed 2000 RPM.

Anyone got a 5-4.5 Warn or Yukon hub kit they want to sell cheap?

 

[blondejoncherokee]

New pinion bearings? how are the carrier bearings? any odd wear on the gears?

so you pulled front shaft, and no vibes. put front shaft on the rear, and no vibes.

what is your DS angle up front? 0 degrees is bad, but with only 3.5" lift, your DS angle shouldnt be too steep, maybe 12* or less ? . get that pinion pointed as high as you can while still maintaining at least 4* of positive caster, obviosuly having as much positive caster is important. if not more. in the rear its more important to have pinion 1-3* below DS angle, the front you have a little more room.

you have swapped front tires to rear and vice versa? you are 100% positive they are balanced?

 

[G2WANIT]

Personally I think you should continue searching to solve the problem, but in the meantime, no need to completely remove the DS, just unbolt it from the axle and bungee it to the jeep somewhere. Won't spin in 2wd... broke my front yoke in Reno, bungee'd the shaft to a control arm and drove it 500 miles home with no problems. Just keep it clear of the axle yoke!

Also, when I was at 6" of lift with 33s, 4.56s, short arms, on a low pinion d30 I could do 80 with no more vibes than what could be attributed to the tires. Not bragging' just want to let you know people do it all the time. Sorry I don't know what my secret sauce was...

 

[lazyxj]

New pinion bearings? how are the carrier bearings? any odd wear on the gears?
so you pulled front shaft, and no vibes. put front shaft on the rear, and no vibes.
what is your DS angle up front? 0 degrees is bad, but with only 3.5" lift, your DS angle shouldn't be too steep, maybe 12* or less ? . get that pinion pointed as high as you can while still maintaining at least 4* of positive caster, obviously having as much positive caster is important. if not more. in the rear its more important to have pinion 1-3* below DS angle, the front you have a little more room.
you have swapped front tires to rear and vice versa? you are 100% positive they are balanced?

Done all of the above and more. My driveshaft guy that told me that the front CV joint has too much angle, at 15.5 degrees, for smooth running at freeway speeds.
At 4's of lift, the engine/transmission has a 5.5 degree rearward slope.
The rear CV shaft has a 12 degree rearward slope and the front has a 10 degree forward slope.
The front shaft is handicapped by having the drive-line slope the opposite direction of its shaft, leading to its very high angle of 15.5 degrees.
The rear shaft benefits from the drive-line slope, reducing its combined angle to 6.5 degrees, well within the CV joints ability to handle without vibrations. It drives fine with the front shaft removed.

The gears have been recently redone to 4.56s (with new gears,bearings and locker), the front yokes replaced with other good ones. The shaft have been swapped, rebalanced and then new one was built for the front (due to a loose slip joint). The shafts appear to run true.
The transfer case has been replaced with a new one. Basically, nothing of the original front setup is left except the axle housing and the vibration.
I'm out of possible solutions other than either removing the shaft or switching to lock-outs, a very expensive proposition.

The front pinion is aimed straight at the front shaft, off 1/2 degree, per FSM, to promote roller bearing movement in the front u-joint. This give 5 degrees of caster, when used with 2 degree offset lower ball joints.
Three set of tires have been tried, in both 31"s and 33"s with zero effect other than changing the speed at which the vib become noticeable.

My XJ has had some form of front shaft vibration ever since it was lifted. On the old 4.11s and 31"s. it started around 70 MPH and was even higher with 33"s, faster than what I normally cruise at. The 4.56s dropped the speed the vibs appear at down 10% or so, bringing the vibs down into the my normal cruising range.
Chrysler knew the stocks XJs were prone to front shaft vibs, leading them to the expense of equipping them with CV front shafts.

Sure miss the locking hubs my older 4X4s had.

 

[kastein]

I'm surprised you can't balance out the vibration at the CV end - the CV H-block itself must be unbalanced or non symmetrical in some way. Of course, I don't think anyone actually balances those parts individually, just the whole assembly.

 

[lazyxj]

I'm surprised you can't balance out the vibration at the CV end - the CV H-block itself must be unbalanced or non symmetrical in some way. Of course, I don't think anyone actually balances those parts individually, just the whole assembly.

Have tried two used shafts re-balanced, one with a new CV assy, a stock shaft and then a complete new shaft. Wish that was the problem but so far, different shafts have not made much of a difference. All the shafts were built by different shops.
I'm running out of things to check or change. Wonder what changing the front shaft's phasing would do?
I'm open to suggestions.

CV joints are nothing more than two couple u-joints and they too suffer the same speeding up and slowing down situation, when spinning, as a regular u-joint. The advantage is the angle change being spread over two u-joints instead of one. 15.5 degrees is 7.75 degrees of change per u-joint, excessive according to every chart I have found, when spun over 2000 RPM. My freeway cruise RPM, with the 4.56s, is 2400-2600.
This would not be a problem for a trail only rig that that rarely sees 60 MPH but for a DD, that is freeway driven, it is a major annoyance.

Hmmm, 35"s would push the vibs back over 70 MPH....it's endless.
It might be easier and cheaper to buy a stock XJ and use it for my DD.

 

[MoparManiac]

Do you still have a LP30 up front?

I'd go through the effort of switching to a HP30 if it's that bad.

 

[kastein]

Have tried two used shafts re-balanced, one with a new CV assy, a stock shaft and then a complete new shaft. Wish that was the problem but so far, different shafts have not made much of a difference. All the shafts were built by different shops.
I'm running out of things to check or change. Wonder what changing the front shaft's phasing would do?
I'm open to suggestions.

CV joints are nothing more than two couple u-joints and they too suffer the same speeding up and slowing down situation, when spinning, as a regular u-joint. The advantage is the angle change being spread over two u-joints instead of one. 15.5 degrees is 7.75 degrees of change per u-joint, excessive according to every chart I have found, when spun over 2000 RPM. My freeway cruise RPM, with the 4.56s, is 2400-2600.
This would not be a problem for a trail only rig that that rarely sees 60 MPH but for a DD, that is freeway driven, it is a major annoyance.

Hmmm, 35"s would push the vibs back over 70 MPH....it's endless.
It might be easier and cheaper to buy a stock XJ and use it for my DD.

yeah... the other part of the theory of how CV joints avoid vibration is that the two ujoints are always perfectly in phase and (theoretically) the centering ball setup keeps the angle on them exactly the same. What that means is that there isn't any rotational speed difference between the tcase output yoke and the driveshaft tube itself, which significantly reduces vibes, but the H block itself still speeds up and slows down with respect to the tcase yoke and the tube. If the H block is unbalanced (i.e. its rotational center of mass isn't exactly on the axis of the ujoints) it'll increase the vibes, but now that I think about it, the vibes you are feeling are probably mostly from the H block itself speeding up and slowing down as it rotates. No real way to fix that other than going to a ball and cup style CV.

 

[mako my day]

Still same boat here. I have not tried different wheels and tires. I only assumed that my tires were fine because they are new and freshly balanced. Tonight I will swap in a set of wheels from my swagger wagon and test drive it again.

 

[Kevin108]

Definitely sounds like you guys are on the right track. Ain't geometry a bitch?

 

[Kevin108]

Hey man, just for shits and giggles, have you tried another set of tires that are the same size? One of the guys in my Jeep club has been fighting death wobble forever on his TJ. Seems like he got a defective set of Yokohamas or they just have a ridiculously soft sidewall that had enough play on 32 to oscillate. Could be your vibes are a similar issue without going into full-blown DW?

 

[bobnoxious]

It's not a balance issue...it's a geometry/shaft operating angle issue. I commend the OP for how much effort and thoroughness has gone into eliminating this, but at this point it's a product of a physics/geometry formula, and something needs to be removed/changed in order to change the current result.

3 choices are:

-remove lift
-regear to a ratio that lowers the driveshaft speed below the vibration threshold
-install a L/O hub kit to stop the front shaft from spinning

 

[magimerlin]

Post pics of your front pinion angle......

 

[yossarian19]

What about stretching wheelbase to decrease driveshaft angle & maybe switch to a heavier shaft.
That seems like it would help, but I'm pretty far from expert here.

 

[mako my day]

I fuxed with my alignment and pinion angles again, but still same issue. Still have not tried different wheels and tires yet though.
I may have it aligned today to see if any changes occur.

 

[Talyn]

Those that have had their shafts rebalanced, if you are using the same shop you may want to try another. I've had good luck with Long Island Driveshafts and Denny's Drive Shafts. Not so much with Tom Woods.

 

[mako my day]

I had mine balanced to 3200 rpm. Their standard is 2800.

 

[Talyn]

I had mine balanced to 3200 rpm. Their standard is 2800.

At 60 mph your drive shaft would be spinning at 2873 RPM, at 70 mph, 3352 rpm. That is assuming an AW4. Seems like a pretty low standard.

 

[srmitchell]

I have pretty much given up. I just stay below 65 mph, I save gas too. I spend so much money trying to fix stuff that can't be fixed that I have no gas money. lol