Vibrations after lift at around 50mph

basic

basic

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Details -
2006 LJ (non-rubicon) with 42LRE auto. 100500 miles.

Just installed rock krawler 3.5 inch max travel lift to replace 2" budget boost. Rancho 9000XL shocks. The ZJ tie rod upgrade as well.

Lift included adjustable front lower control arms, adjustable rear uppers, rear track bar bracket; adjustable front track bar, front and rear sway bar links, extended brake lines. Maybe some other stuff I may be missing?

Prepping to get it aligned next week.

The issue:
Before this lift; i had a bit of a wobble in the front that is now gone - attribute that to new tie-rod and track-bar.

HOWEVER - now, at around 50mph, I get a bit of a vibration that wasn't really there before. From what I can read online, driveline vibes from pinion angle issues seem to be at all speeds - this is only for a few MPH at around 50. The vibration is in the rear, as I don't feel it at all through the steering.

Would driveline angles being off cause something like this? As I have an LJ, I do not have an SYE as I was hoping to get away without one. Not 100% sure I got the driveline angle correct. I think it's approx. 2 degrees lower (more horizontal) than the driveshaft. The alignment shop I'm taking it to came highly recommended from the guys at completeoffroad.com (local shop with lots of experience but no alignment machine). The other thing is it *may* be tires, but I didn't experience this vibe before the lift.

I pulled the front driveshaft to eliminate that, no change.

Any Thoughts?
 
It's more than likely your rear pinion / driveshaft angle, I'd almost bet on it. If you don't get it pretty spot on, then you'll most certainly get the types of vibrations you're experiencing.
 
Ah, so it could be at a certain speed. From what I was reading it would be immediately noticeable and at all speeds.
 
It's your rear driveshaft, just fixed that same issue at 50-54 mph.. it's time to shop for a sye kit
basic said:
Details -
2006 LJ (non-rubicon) with 42LRE auto. 100500 miles.

Just installed rock krawler 3.5 inch max travel lift to replace 2" budget boost. Rancho 9000XL shocks. The ZJ tie rod upgrade as well.

Lift included adjustable front lower control arms, adjustable rear uppers, rear track bar bracket; adjustable front track bar, front and rear sway bar links, extended brake lines. Maybe some other stuff I may be missing?

Prepping to get it aligned next week.

The issue:
Before this lift; i had a bit of a wobble in the front that is now gone - attribute that to new tie-rod and track-bar.

HOWEVER - now, at around 50mph, I get a bit of a vibration that wasn't really there before. From what I can read online, driveline vibes from pinion angle issues seem to be at all speeds - this is only for a few MPH at around 50. The vibration is in the rear, as I don't feel it at all through the steering.

Would driveline angles being off cause something like this? As I have an LJ, I do not have an SYE as I was hoping to get away without one. Not 100% sure I got the driveline angle correct. I think it's approx. 2 degrees lower (more horizontal) than the driveshaft. The alignment shop I'm taking it to came highly recommended from the guys at completeoffroad.com (local shop with lots of experience but no alignment machine). The other thing is it *may* be tires, but I didn't experience this vibe before the lift.

I pulled the front driveshaft to eliminate that, no change.

Any Thoughts?
Click to expand...

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If you don't, you'll be replacing u joints 2-3 times a year depending on how much you drive..and as the u joints go, the vibrations will get worse and worse. I went with teraflex sye and Adam's super short driveshaft, I would recommend them both

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Thanks for the info. I was hoping I could get away without an SYE because it's an LJ. Seems the consensus online is that you could go to about a 4-4.5" lift with an LJ before needing an SYE.

@Wesley Herndon - do you have an LJ or TJ and how much lift?
 
basic said:
Thanks for the info. I was hoping I could get away without an SYE because it's an LJ. Seems the consensus online is that you could go to about a 4-4.5" lift with an LJ before needing an SYE.

@Wesley Herndon - do you have an LJ or TJ and how much lift?
Click to expand...

In most cases that is true, you can get away without a SYE on an LJ with more lift. However, it varies from LJ to LJ, and nothing is for certain.

One way to tell for sure if it's the rear driveshaft is to drop your transferase an inch or so with some washers. If that fixes the issue, then you know it's time for a SYE.

Oh, if you do that, make sure you get longer bolts, since the stock ones will be too short!
 
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I have a 06 tj 4.5 inch, but that is not true, my brother has a 05 Lj 4 inch and he has to replace u joints about 3 times a year,and has gone 6 months a year
basic said:
Thanks for the info. I was hoping I could get away without an SYE because it's an LJ. Seems the consensus online is that you could go to about a 4-4.5" lift with an LJ before needing an SYE.

@Wesley Herndon - do you have an LJ or TJ and how much lift?
Click to expand...

Sent from my SM-G892A using Tapatalk
 
I'll try dropping the trans case tomorrow with the washer trick. Any idea what bolts are required?

Maybe it's time for a MML! That's in the planbook anyway when I get a BL and tummy tuck. Was planning to do the MML with a body lift, but could do the MML seperately now.
 
basic said:
I'll try dropping the trans case tomorrow with the washer trick. Any idea what bolts are required?

Maybe it's time for a MML! That's in the planbook anyway when I get a BL and tummy tuck. Was planning to do the MML with a body lift, but could do the MML seperately now.
Click to expand...
I can’t recall, I about 98% sure the bolts are metric. Remove one of them and take it to the store with you. It will be fine driving without it. I went without one for about 5 months one time.

I do think it’s strange that you would be getting driveline vibes with 3.5” on an LJ though. Tires would be suspect in my book, especially since they are only in the 50-54mph range. I have had similar in the past and it was always tires. Even when I had them perfectly balanced twice (Ahem), they still caused a speed related shimmy. Only when I got new tires did it completely and immediately disappear.

I did exactly what you suggested possible, added the MML and did the BL later. It is ideal to do them at the same time, and you will have to move the fan shroud up an inch if you just do the MML, which also requires trimming a bit of the shroud below the radiator hose, but it’s easy enough to do.
 
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From what I can find online, it's M12x1.75. Seems easy enough to try. I'll double check driveshaft angle as well. Maybe the angle is just off and I can adjust the vibes out.
 
basic said:
From what I can find online, it's M12x1.75. Seems easy enough to try. I'll double check driveshaft angle as well. Maybe the angle is just off and I can adjust the vibes out.
Click to expand...
I think your pinion is supposed to be parallel to the yoke on your non-Rubicon. YOu definitely don’t want it pointing at the yoke. You only do that when you get the SYE and DC

P.s. those bolt sizes sound correct. Just make sure they are correct, you don’t want to mess up the nutserts in the frame if you can help it!

And for the test, you really only need the four corners of your TCase dropped. I know it’s only saving a couple of dollars, but it’s not really necessary to get all six just for a test
 
Thanks for the help guys. I'll take a better look at it in the daylight tomorrow, see what I can do for the angle (I may have measured wrong - seems the best place to measure is the flat spots on the back of housing? I can't remember where I measured - I think I pulled the driveshaft and checked the flat of the yoke).
I also need to notch spring perches for shocks and reinstall front driveshaft. Hopefully warms back up a bit.
 
basic said:
I'll try dropping the trans case tomorrow with the washer trick. Any idea what bolts are required?

I will suggest abandon hope on this. LJ shovel is really low and lowering it more is not some you may enjoy it after the lift install.

Maybe it's time for a MML! That's in the planbook anyway when I get a BL and tummy tuck. Was planning to do the MML with a body lift, but could do the MML seperately now.
Click to expand...

You are more that correct, its time for a MML.
My LJ'er suggestion is to get the JKS blocks that goes between the motor mount and the frame or get a motor mount that has rubber, stay away from the poly if you can be disturbed by certain vibes.
 
Its could be a few things. Tires are a possibility but not likely and they weren't changed. Rotate them front to back to see if it changes.

Drive shaft angle could be it, you need the pinion parallel to the tcase output (but you know that) it should be bang on, all the info that says to put it a few degrees low is old leftover leaf spring info, for a tj it should be exactly the same.

U joints. The trunions on a ujoint work themselves into a groove over time. When you change the operating angle of the joints with a lift it can cause vibes that are solved with a fresh set of joints.

All are fairly easy and inexpensive fixes, I'd start with the 2 free ones first ;)

—
There must have been a time
when we could have said no.
 
As stated, if you can get the output shaft of the transfer case and the rear pinion parallel with each other, then test, let us know if that makes a difference.

Some owners do experience vibrations from drive shaft angles only at certain speeds...
 
You have adjustable control arms; have you tried to make any adjustments? I would try that before making installing a mml or dropping the skid.
 
Thanks for the additional feedback. after looking at it closer this morning - it seems my angles are definitely off and I can't get them much better. I've made the rear uppers as short as I can, and still the angle is too much to get the input angle the same as the output angle. A MML and/or TC drop would help some, but still not good.

Where it the best place to measure the angle of the transfer case output? using the flat spot on the back of the rear diff works great for the rear pinion angle - just not sure where to measure the front.

I think the best thing may be to pick up a set of rear-lower control arms to push the bottom out and drop the pinion angle. Even with the uppers all the way in, the angle is almost straight. Maybe an SYE and driveshaft would help, but I think I'll still need something to drop the pinion angle further.

20180512_124649.jpg
 
You will probably have to pull the driveshaft and measure the output shaft on the case, based on that pic. It isn't exactly true that "uppers adjust angle and lowers adjust length" as they work together to do both. Adding adjustable lowers will get you where you need to be.
 
Yep. As an interim fix, I think I'm going to try use some washers to drop the TC and see if that helps clear up the vibes. Jeep is my daily when it's raining, and wouldn't ya know - Thunderstorms next week. I could risk the motorcycle, but getting caught in a thunderstorm on a motorcycle is not my idea of fun. Probably going to be investing in a MML and then removing the TC drop. We'll see where that gets me.
 
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