Rear Driveshaft vibes

Speedy_RCW

Speedy_RCW

Hooked
Hey guys,

As I mentioned in my build thread, I just had my 4.10's swapped with 5.13's on my JKU and now have what seems to be a driveshaft vibe. I thought it was coming from the front since it's an aftermarket CV shaft (with less than ideal pinion angle) so I pulled it and still have a vibe that starts around 45 and seems to clear up at 60. Don't wanna go up past 60 while i'm breaking in the gears. Since I'm not entirely sure it's only the rear vibrating I still need to mount the front back up and remove the rear and take it for a drive to verify. But my question is in regards to the rear shaft vibration. Should I get rear UCA's to bring the pinion angle back to stock or just spring for an aftermarket shaft with stock arms? I'll eventually do both but can only do one right now as budget is limited. Eyeballing it, the pinion angle looks pretty ideal for a CV shaft. Being that I installed 3.5" suspension with stock rear arms the pinion looks tilted enough to be pointing right at the TC output but I haven't put an angle finder on it or anything. Has anyone else experienced driveshaft vibrations with the stock shaft after doing gears? I don't know shit about the rzeppa joint but thought angles weren't as critical with it for some reason. Anyways, thanks in advance.
 
You shouldn't have ANY vibrations with a factory shaft with its rzeppa joints regardless of your pinion or at least, not if it's balanced and the bearings aren't going bad. That being said, if you get an aftermarket shaft, you will NEED rear adjustable upper control arms to set your pinion.
 
I don't know much about jks but I had a bad rear driveshaft vibration that was due to it being way out of balance and and when I took it out the u joints pretty much fell apart.
 
wayoflife said:
You shouldn't have ANY vibrations with a factory shaft with its rzeppa joints regardless of your pinion or at least, not if it's balanced and the bearings aren't going bad. That being said, if you get an aftermarket shaft, you will NEED rear adjustable upper control arms to set your pinion.
Click to expand...

Thanks Eddie, I see now that a rzeppa joint is just basically a birfield or give it whatever name ball and socket joint. On my way home I started to get a slight clunk when I hit the brakes. I'm starting to suspect the gear setup. My driveshaft speed has only increased 25% with the new gears and I could run 90mph before the swap with no vibe, so balancing doesn't even make sense. And as you pointed out, the angle shouldn't matter. The vibe I have peaks at about 50mph which is the equivalent to 62 prior to gear swap. But what's got me is that it's a pulsating hum like you would get with an out of time u joint shaft. Could the gear setup be causing the same type of hum? The clunk is another concern, I can't really tell where it's coming from but I don't think it's the driveshaft because it's only when I'm in a forward gear and hit the brakes. So it's basically maddening. I'm supposed to be driving the jeep to WA in a month and wanna get this figured out. May end up having to take the wife's car. Thanks for your input.
 
Found the clunk. Seems the shop didn't tighten the drivers side caliper bolts. Top one fell out so when I hit the brakes the caliper would rotate and make contact with the dust shield. Now just gotta figure out the vibration problem.
 
*UPDATE* Put a dial on the rear pinion flange today and I found about 10 thousandths play vertically and i can move the flange in and out about 5 thousandths. Called the shop back up and I'll be dropping in back off this Friday. Hoping that this is the source of the vibration. I'll keep this thread updated as I work through this problem.
 
Speedy_RCW said:
*UPDATE* Put a dial on the rear pinion flange today and I found about 10 thousandths play vertically and i can move the flange in and out about 5 thousandths. Called the shop back up and I'll be dropping in back off this Friday. Hoping that this is the source of the vibration. I'll keep this thread updated as I work through this problem.
Click to expand...

What is spec for both measurements? Or should it have zero play?
 
WJCO said:
What is spec for both measurements? Or should it have zero play?
Click to expand...

Zero according to the shop. If the pinion is moving that's affecting preload and depth. But I'm just going by what they say. Gears is the one thing I won't do myself.
 
Speedy_RCW said:
Zero according to the shop. If the pinion is moving that's affecting preload and depth. But I'm just going by what they say. Gears is the one thing I won't do myself.
Click to expand...

I've always gone by feel there too and don't expect play there either. Engine bearings allow for about .003 of clearance for oil to circulate, but as far as roller bearings, I don't know if there is even a spec for lateral play :idontknow: . But either way, glad you got out the tools just to see where you were at. Hope you get it fixed.
 
So the shop that did the gears did admit that there was too much play in the pinion. They replaced the gear set and bearings. Picked it up last night and the vibration is still there. Not as bad as it was but still there. Everything feels solid and there's no pinion movement anymore. Shop is saying its driveline related and I have to agree it does seem like a driveline due to the pulsing vibration. It's just still hard for me to understand since I'm running the stock shaft. But I'm going to bite the bullet and get an aftermarket shaft and rear UCA's. It was on my list to buy anyways and hopefully that will take care of the vibe.
 
So I installed the new shaft today. Vibration is still there. Pulsating vibration just before 40mph and again when I get close to 50 and up. New shaft and vibes in the exact same spot. What else could I be missing? Can a bad gear setup cause pulsating vibrations? I don't want to keep dropping coin on this thing. It's really pissing me off. Any ideas?
 
I just swapped out gears to 4.56 with True-tracs front and rear from 3.21s. Having a very similar vibration issue at freeway speeds.

It's a humming cyclical vibe coming from seems like rear driveshaft area. The rear driveshaft is stock. Replaced the rear UCAs and there is some more adjustment that can be done to align pinion better, but based on some higher up comments, does not seem like this would be the root of the problem. There's about 3.5 - 4 inches of lift.

Very curious if you get to the bottom of this. Im headed back to the shop this week for another look. I am wondering if the factory shaft is unbalanced and it was not having an impact with the 3.21s.

Any advice here would be appreciated.
 
Last edited:
Speedy_RCW said:
So I installed the new shaft today. Vibration is still there. Pulsating vibration just before 40mph and again when I get close to 50 and up. New shaft and vibes in the exact same spot. What else could I be missing? Can a bad gear setup cause pulsating vibrations? I don't want to keep dropping coin on this thing. It's really pissing me off. Any ideas?
Click to expand...

JeepFan just had a similar problem and found that there was a slight runout on the pinion yoke and the spec for it is zero. Needless to say, he ended up replacing the yoke and the the vibration was gone. Not saying that this is your problem but it could be that you have a pinion or output shaft yoke nut that isn't tightened to torque spec. Being that you just had gears installed, I could see that being a problem especially if your shop reused your old crush sleeve. A loose nut will allow for enough movement to cause vibrations.
 
jpone said:
I just swapped out gears to 4.56 with True-tracs front and rear from 3.21s. Having a very similar vibration issue at freeway speeds.

It's a humming cyclical vibe coming from seems like rear driveshaft area. The rear driveshaft is stock. Replaced the rear UCAs and there is some more adjustment that can be done to align pinion better, but based on some higher up comments, does not seem like this would be the root of the problem. There's about 3.5 - 4 inches of lift.

Very curious if you get to the bottom of this. Im headed back to the shop this week for another look. I am wondering if the factory shaft is unbalanced and it was not having an impact with the 3.21s.

Any advice here would be appreciated.
Click to expand...

I'll keep this thread updated as to what I find.

wayoflife said:
JeepFan just had a similar problem and found that there was a slight runout on the pinion yoke and the spec for it is zero. Needless to say, he ended up replacing the yoke and the the vibration was gone. Not saying that this is your problem but it could be that you have a pinion or output shaft yoke nut that isn't tightened to torque spec. Being that you just had gears installed, I could see that being a problem especially if your shop reused your old crush sleeve. A loose nut will allow for enough movement to cause vibrations.
Click to expand...

I checked the runout on the old pinion flange which was 0. The new driveshaft came with a new yoke for the pinion and a new transfer case flange. This is the second gearset, and second driveshaft with the vibe in the same spot. I'll check runout on both the pinion yoke and TC flange just to rule that out as well. I check the pinion yoke yesterday and it's tight with no movement. Right now my pinion is pointing 1 degree too high for the new driveshaft so I started dialing pinion angle last night but didn't get finished. I don't think 1 degree would cause an issue though, at least not much of one. But I gotta make sure the angles are perfect. If the vibe is still there, I'm planning on taking down to a local driveline shop and see if they can balance the shaft or diagnose the problem. Maybe it's off balance straight from the manufacturer but I highly doubt that since the vibe is at the exact same speed as the factory shaft. Feel like beating just beating my head against a wall but I gotta get this figured out. Thanks for the tips and if you got anymore, please shoot them my way. Heading up north for 10 days so won't be making much progress for the time being.
 
Speedy_RCW said:
Right now my pinion is pointing 1 degree too high for the new driveshaft so I started dialing pinion angle last night but didn't get finished. I don't think 1 degree would cause an issue though, at least not much of one. But I gotta make sure the angles are perfect.
Click to expand...

You've got to remember that your pinion will LIFT as you step on the accelerator. That will add to your angle by at least a degree or more depending on the condition of your control arm bushings. That could be your problem right there.
 
wayoflife said:
You've got to remember that your pinion will LIFT as you step on the accelerator. That will add to your angle by at least a degree or more depending on the condition of your control arm bushings. That could be your problem right there.
Click to expand...

Would you suggest setting it 1 degree low? I've heard both ways but was planning on setting it at 0. You've got more experience and knowledge than me so I'll take your advice. Thanks again.
 
Speedy_RCW said:
Would you suggest setting it 1 degree low? I've heard both ways but was planning on setting it at 0. You've got more experience and knowledge than me so I'll take your advice. Thanks again.
Click to expand...

No. I would recommend setting the pinion dead on with the shaft. The slight amount of lift will not matter. I was just pointing out that it might be a problem for you being that you have your pinion sitting to high already.
 
wayoflife said:
No. I would recommend setting the pinion dead on with the shaft. The slight amount of lift will not matter. I was just pointing out that it might be a problem for you being that you have your pinion sitting to high already.
Click to expand...

Gotcha. I'll set it dead on and see what happens. Thanks.
 
You must log in or register to reply here.
Top Bottom