Jeep Re-gear Vibrations

[catbones2010]

Hi all!

There's so many posts on this but all from like 4+ years ago regarding this issue. I see some solved it and some did not, or at least that's where the conversation ended.

I've got a 2006 Jeep LJ with 33" tires, 2" lift, non-rubicon, regeared to 5.13 for future 35s. I've developed vibrations right after the re-gear and reading through everything for the past week, I've done the following;

- Tested all driveshafts, vibrations = YES with front driveshaft on, rear removed, front and rear on, 4wd on.
- Tested Front driveshaft removal, NO vibrations
- Driveshaft angles are fine within 1 degree or 0.5 degree. Front Driveshaft angle vs pinion is 4.5 driveshaft, pinion 5.

Now the only difference I'm noticing and being helped by few other members, is the sound and vibration itself. Those who had it, state mine don't sound like a pulsaing harmonic sound vibration. Second, once ago, I drove it on thruway at 85 or so, and it sounded, felt exactly the same, slightly less I would say. Obviously, might of sounded and felt the same if I got to 90-95mph but I didn't. I'll post my video, maybe someone made one too, to compare or if you can tell. Mine vibration is constant, doesn't pulsate, yes, it vibrates, yes, theres slight sound to it, sound is like I state in the video, if I took a hand portable sander, turned it on and left it on the carbet of the jeep.

Here's a short video; https://www.dropbox.com/scl/fi/khi7...333a.mp4?rlkey=1646zyb6k7jjs14hsa6yltuzy&dl=0

Any help is appreciated, if you fixed it, please share how, without the statement "hub kit", I'd rather not go that way defeating the transfer case funtionality.

Thank you in advance!

 

[97JadeTJ]

When I regeared my old Tj to 4.88 I had a high speed harmonic vibration… I pulled the rear driveshaft out and replaced the ujoints (which didn’t seem bad) and that solved the problem…

 

[catbones2010]

When I regeared my old Tj to 4.88 I had a high speed harmonic vibration… I pulled the rear driveshaft out and replaced the ujoints (which didn’t seem bad) and that solved the problem…

I see, did it sound similar to the sound in my video? I apologize, you might have to turn up the sound on that video as for some reason iPhone made that sound seem not as loud but you can hear at 65-70, my dash pieces are dignging kinda sound from the vibration in the background as well.

 

[97JadeTJ]

I put a 2 1/2 inch lift on my old Jeep with no drive line vibrations, but others have reported drive line vibrations with his little as a 2 inch lift… If you wanna know if it’s drive line vibrations do a skid plate drop with about 1” of washers and see if the vibration is still there…

 

[97JadeTJ]

I see, did it sound similar to the sound in my video? I apologize, you might have to turn up the sound on that video as for some reason iPhone made that sound seem not as loud but you can hear at 65-70, my dash pieces are dignging kinda sound from the vibration in the background as well.

My hearing sucks so I really couldn’t hear it, but I believe you… At 65 miles an hour with 513 gears that driveshaft is spinning fast…

 

[catbones2010]

I put a 2 1/2 inch lift on my old Jeep with no drive line vibrations, but others have reported drive line vibrations with his little as a 2 inch lift… If you wanna know if it’s drive line vibrations do a skid plate drop with about 1” of washers and see if the vibration is still there…

Well, that would make sense however I had no vibrations at 60, 70, with the current lift of 2". The lift was done a little over a year ago. Now right after gear change, these vibrations stated. Smooth as butter at 60, 65, 70... that one time, at 80-85 or higher, felt very very similar to my vibrations now I get with the regear but at 65 which makes sense, 65 is pretty much 95 now. I am leaning towards driveshaft replacement.

I did the ujoints 4 months ago, all new, but maybe I didn't do a good job and nothing showed until now. Just thought I'd pick other peoples brains few years later to see if anyone fixed it afterwards, how, with what, what worked, and maybe even can tell me how it sounded. Maybe same as in video, or not. If not, than maybe I have a different driveshaft vibration. That's what I'm trying to establish.

All I hear a lot say when speaking about high speed harmonic vibration is that it is a sound that comes and goes with 1 to 2 second intervals. Mine feels constant.

 

[OldBuzzard]

Since this all started when you regeared, that implies that the now faster turning driveshafts are the problem. Essentially all driveshaft manufacturers and repair shops balance driveshafts to about 3000 RPM. On 33" tires, with 5.13s, your driveshafts are doing about 3700 RPM at 70 MPH. It probably has little or nothing to do with the angles, especially on an LJ with only a 2" lift. It's probably just driveshafts which aren't perfectly balanced, especially for >3000 RPM.

There was a thread on here, somewhere, about someone finding a single shop which could balance to a higher speed.

I would recommend calling Shawn at Tom Wood's Custom Drive Shafts 801-737-0757 and discuss this with him. He's extremely helpful, and may be able to recommend something, or to rebalance your driveshafts.

 

[MightyJoe]

Likely driveshaft balance. Can take it to any local driveshaft shop and have it balanced for about $100

 

[catbones2010]

Agreed. Some state driveshaft balancing doesn't fix it, so I was just trying to compare sounds and vibrations. That said, I got a local shop here that does driveshafts for race cars and such, they claim they can balance (if needed) their driveshafts up to 10k rpms. I've emailed them to see if they can do mine up to 4000rpms if I buy new one from them. I'd do my old one, but its 20 years old, some surface rust, and new is thicker, probably better, with newer joints as well even though I've rebuilt mine. New will give me the extra assurance I didn't mess something with ujoints 6 months ago or less. I'll see what they'll say on the 4000 rpms balance. I also don't see speeds on thruways here higher then 65-70 anyways so if I get vibes after that with new driveshaft balanced for 3500rpms or 4000rpms, I'm good to live with it

 

[MightyJoe]

Agreed. Some state driveshaft balancing doesn't fix it, so I was just trying to compare sounds and vibrations. That said, I got a local shop here that does driveshafts for race cars and such, they claim they can balance (if needed) their driveshafts up to 10k rpms. I've emailed them to see if they can do mine up to 4000rpms if I buy new one from them. I'd do my old one, but its 20 years old, some surface rust, and new is thicker, probably better, with newer joints as well even though I've rebuilt mine. New will give me the extra assurance I didn't mess something with ujoints 6 months ago or less. I'll see what they'll say on the 4000 rpms balance. I also don't see speeds on thruways here higher then 65-70 anyways so if I get vibes after that with new driveshaft balanced for 3500rpms or 4000rpms, I'm good to live with it

How much is a new one?

I just had my '94 landcruiser shafts serviced with new joints, grease, balance, and cleaned and painted for $150 and they are 30 years old. My Tacoma has a knack for candy caning the rear shaft (hits rocks) and I would have it rebuilt (cut, weld new tube, balanced, etc) and that was usually $300.

Costs vary of course but don't be afraid to run the old ones if serviced correctly.

 

[catbones2010]

How much is a new one?

I just had my '94 landcruiser shafts serviced with new joints, grease, balance, and cleaned and painted for $150 and they are 30 years old. My Tacoma has a knack for candy caning the rear shaft (hits rocks) and I would have it rebuilt (cut, weld new tube, balanced, etc) and that was usually $300.

Costs vary of course but don't be afraid to run the old ones if serviced correctly.

It would cost me like $450 for the front or $100-150 to redo. I'm also thinking newer is 2.5 tubing, while factory I think was 2 or little less than that, so strength could play a role here too. Tim Woods only balances them to their machines max which is 3300rpm, but he also offers a longer joint shaft, making it stronger more then just 2.5 tubing.

 

[Harold&Cat]

We recently went to 4.88 gears and now have the vibration and noise . I pulled the front driveshaft and it is quiet and smooth . The front shaft is original with at least one worn out u-joint and a little play in the slip joint . I will be ordering new front and rear driveshafts from Tom Woods very soon . I don't want a larger tube on the front shaft because it doesn't have much room to drop during articulation. It will hit the cross member if it drops too much with a larger diameter shaft .

 

[catbones2010]

We recently went to 4.88 gears and now have the vibration and noise . I pulled the front driveshaft and it is quiet and smooth . The front shaft is original with at least one worn out u-joint and a little play in the slip joint . I will be ordering new front and rear driveshafts from Tom Woods very soon .

Let me know how yours goes... I've read so many different stories, some worked out the issue, some didn't. Kinda bummed about doing regear but we will see if new, well balanced one works. Just for info from research yoke some say doesn't run properly to start with, but not enough rpms spinning to be noticable or to show any signs of issues under 2500rpms, they replaced it and vibes went away... others rebuilt their tcase, but who knows if they also replaced the yoke or not.

 

[tnjeepguy]

My advice, do not drive 85 in a TJ Jeep.

 

[Blackjack]

What diameter is the tube on your existing driveshaft?

With 5.13 gears and 33s your driveshaft speed at 65 mph is hovering around 3400 rpm give or take. So your driveshaft needs to be in good working order and very well balanced.

An even after you get 35s I would avoid trying to drive fast.

88 MPH on 33s is 4600 RPM and 35 is 4350 which is a lot(I would argue too much) to ask out of a short and heavy driveshaft.

 

[catbones2010]

What diameter is the tube on your existing driveshaft?

With 5.13 gears and 33s your driveshaft speed at 65 mph is hovering around 3400 rpm give or take. So your driveshaft needs to be in good working order and very well balanced.

An even after you get 35s I would avoid trying to drive fast.
View attachment 516652

88 MPH on 33s is 4600 RPM and 35 is 4350 which is a lot(I would argue too much) to ask out of a short and heavy driveshaft.

Not trying to drive fast, but I'd like to do 65 on the thruway.

 

[catbones2010]

My advice, do not drive 85 in a TJ Jeep.

Not what I was getting at, no where do I state I want to do 85 constantly

 

[AndyG]

What diameter is the tube on your existing driveshaft?

With 5.13 gears and 33s your driveshaft speed at 65 mph is hovering around 3400 rpm give or take. So your driveshaft needs to be in good working order and very well balanced.

An even after you get 35s I would avoid trying to drive fast.
View attachment 516652

88 MPH on 33s is 4600 RPM and 35 is 4350 which is a lot(I would argue too much) to ask out of a short and heavy driveshaft.

I’m going to say something that’s not an absolute, but it’s been my experience when your ratio is very high you tend to do better with the pinion in the rear going upward in line with the shaft and a CV driveshaft as far as vibrations-

This doesn’t mean this will solve every problem or that it’s the only way I just have had multiple rigs and the ones that have done the best ended up being set up this way.

Elliptical orbits canceling out at extremely high speed are inherently challenging- The least bit of play in a u joint or shaft imbalance and you’re going to know it.

My TJ Rubicon is geared 4:88-with a stock rear shaft, rebuilt.

It has 2” of lift and vibes at 60 plus to the point my rear pinion seal leaks now -

My LJR is lifted 4” with a full tuck and body lift, has 5:38 , CV shaft, no vibes at all


My former TJR was 4”, 4:56 and vibed until I went CV rear shaft .

Again this is not what everybody has to do to get success but I think you are reducing the potential for problems if you can go that route.

 

[catbones2010]

I’m going to say something that’s not an absolute, but it’s been my experience when your ratio is very high you tend to do better with the pinion in the rear going upward in line with the shaft and a CV driveshaft as far as vibrations-

This doesn’t mean this will solve every problem or that it’s the only way I just have had multiple rigs and the ones that have done the best ended up being set up this way.

Elliptical orbits canceling out at extremely high speed are inherently challenging- The least bit of play in a u joint or shaft imbalance and you’re going to know it.

My TJ Rubicon is geared 4:88-with a stock rear shaft, rebuilt.

It has 2” of lift and vibes at 60 plus to the point my rear pinion seal leaks now -

My LJR is lifted 4” with a full tuck and body lift, has 5:38 , CV shaft, no vibes at all


My former TJR was 4”, 4:56 and vibed until I went CV rear shaft .

Again this is not what everybody has to do to get success but I think you are reducing the potential for problems if you can go that route.

Got it, thank you. Why not just throw CV rear shaft on the 4.88 TJR to take out the vibes? or just didn't get to it yet

 

[AndyG]

Got it, thank you. Why not just throw CV rear shaft on the 4.88 TJR to take out the vibes? or just didn't get to it yet

Well actually I was thinking about calling Tom Woods as I was typing that-

It’s a pretty fresh build so I’m just now sorting out everything and for a while I thought I was going to get it with pinion angle but it’s not gonna happen I think- I’ve got it coming in at 62 plus but that’s the best I can do-

I have another shaft in good condition for a Rubicon I’m going to put on it this evening if the rain lets me back my LJR with the top off out- I’m going to give that a spin without a lot expectation- if no joy then go CV. It has adjustable arms so I am prepared.