4.0, 42RLE, NP241OR High Speed Vibrations After Re-Gear to 4.88 or Deeper

[Mr. Bills]

From Shawn Wood today @ Tom Woods Shafts-———-I had asked them if going to a Conventional Two Joint Drive Shaft might help-—--His reply-—————

. . . What size of tires are you running? Speed could be a factor, if you are geared exceptionally low for your tire size the shaft might just be spinning too fast. . . .

. . . Speed is for sure a factor here. At 60mph your shaft is spinning at about 2,900 RPM. This means that at 60 your shaft is spinning as fast as most people’s shafts are at 70. At 70 your shaft is spinning at the equivalent speed of about 82.

^^ This is the thinking I relied upon most when I decided to convert to manual hubs. Conceptually it makes sense even without the math. With my 5.38 gears, my front driveshaft was spinning at warp speed at 68 mph where my vibrations began. Eliminate the spinning, eliminate the problem.

 

[dougrz]

I read someplace online (that I can no longer find) that the front output bearing for the NV241OR transfer case is rated at a certain rpm and that there is a replacement bearing rated for greater rpm's. The post or article I read even had the part numbes for that bearing. I really wish I could find it now. I'm not confident that it would make any difference in the harmonic/vibration that we are experiencing after a regear to 5.13 or 5.38, but it would be something to try before giving up and/or installing manual hubs.

Has anyone else seen the article or post I am referring to? Have a link per chance?

I see the writer of that post did reply with a link in post #92.

He mentions the stock bearing is rated for 4300 rpm. With 4.88s and 33" tires, for example, that would be reached around 85 mph. With 5.38s and 33s, 78 mph. But he did say it helped.

 

[Mr. Bills]

I see the writer of that post did reply with a link in post #92.

He mentions the stock bearing is rated for 4300 rpm. With 4.88s and 33" tires, for example, that would be reached around 85 mph. With 5.38s and 33s, 78 mph. But he did say it helped.

Thanks for the link, however the high speed bearing referenced in Post #92 is for the NP231, not the NV241OR in the Rubicons. The unanswered question has been whether the bearing referenced in Post #92 (linked below) fits the 241 as well.


https://wranglertjforum.com/threads...ar-to-4-88-or-deeper.12218/page-5#post-236117

https://www.amazon.com/dp/B007EDPEK2/?tag=wranglerorg-20

 

[Josh_Br]

I apologize for reviving an old thread. I read all 14 pages of it and wondered if anyone has found a good solution to this over the past few years. My vibration issue does not have to do with the front driveshaft.

I have a 2004 TJ Rubicon with 180,000 miles. It's a 5 speed. I got it six months ago. It came with a 4" Superlift short-arm lift and 35" tires. It came with 4.88 gears, and the original lockers were shot. It also came with an Adams front driveshaft and a Tom Woods rear driveshaft. Since I got the Jeep, I've done the following to it:

- Replaced the old NV3550 transmission with a brand new AX15.
- Had both axles professionally rebuilt, to include new differentials, new 4.88 gears, and many new bearings.
- Had both driveshafts re-balanced by Adams Driveshafts.
- Put brand new Yokohama tires on it (still 35's).
- Added a JKS Manufacturing adjustable upper rear control arms to correct the pinion angle (currently at -1 degree).
- Added a JKS Manufacturing adjustable rear trackbar because the rear axle was off center about 1/2".
- Had the Jeep aligned.

I get a vibration that begins around 50 mph. It gets worse the faster I go beyond that. It's not to the point of being undriveable, but it does make me concerned that something is eventually going to get damaged. Plus, it's just bothersome. It's like a pulsating vibration, and I feel it in the floor, center console, my seat, and the gas pedal. I do not feel it in the steering wheel. As it pulsates, it almost feels like it goes front to back. Like the vibration is toward the rear, then toward the front, then rear, then front, changing with each pulse. I've done some troubleshooting, but none of it has made any difference. In addition to what I've already mentioned above, I've tried these things:

- Removed the front driveshaft and drove with only the rear.
- Removed the rear driveshaft and drove with on the front.
- Swapped the spare tire for either of the rear tires.

With each of these things, the vibration slightly changes, but it doesn't go away. In all the prior posts, I read one where another guy had the vibration and it wasn't related to his front driveshaft, either. He upgraded the bearings in his transfer case, but he was still getting the vibration to some degree, so it didn't resolve it. I was thinking about this while I was supposed to be sleeping last night, and I thought that maybe the driveshaft/transfer case RPMs are just too high, and maybe I'd go to a higher gear ratio, like 4.65 or even back to 4.10's, just go get rid of it. However, Tom Wood's website has a driveshaft RPM calculator, and I found that there is not much difference in driveshaft/TC RPM with a stock Rubicon (30" tires and 4.10 gears) and my Rubicon (35" tires and 4.88 gears). To be exact:

As you can see, my Jeep is only turning 40 - 50 RPM higher than a stock Rubicon, so I don't think going to a higher gear ratio would solve anything.

So...I'm at a loss. If anyone has any wisdom, I'd be happy to listen.

 

[mrblaine]

I apologize for reviving an old thread. I read all 14 pages of it and wondered if anyone has found a good solution to this over the past few years. My vibration issue does not have to do with the front driveshaft.

I have a 2004 TJ Rubicon with 180,000 miles. It's a 5 speed. I got it six months ago. It came with a 4" Superlift short-arm lift and 35" tires. It came with 4.88 gears, and the original lockers were shot. It also came with an Adams front driveshaft and a Tom Woods rear driveshaft. Since I got the Jeep, I've done the following to it:

- Replaced the old NV3550 transmission with a brand new AX15.
- Had both axles professionally rebuilt, to include new differentials, new 4.88 gears, and many new bearings.
- Had both driveshafts re-balanced by Adams Driveshafts.
- Put brand new Yokohama tires on it (still 35's).
- Added a JKS Manufacturing adjustable upper rear control arms to correct the pinion angle (currently at -1 degree).
- Added a JKS Manufacturing adjustable rear trackbar because the rear axle was off center about 1/2".
- Had the Jeep aligned.

I get a vibration that begins around 50 mph. It gets worse the faster I go beyond that. It's not to the point of being undriveable, but it does make me concerned that something is eventually going to get damaged. Plus, it's just bothersome. It's like a pulsating vibration, and I feel it in the floor, center console, my seat, and the gas pedal. I do not feel it in the steering wheel. As it pulsates, it almost feels like it goes front to back. Like the vibration is toward the rear, then toward the front, then rear, then front, changing with each pulse. I've done some troubleshooting, but none of it has made any difference. In addition to what I've already mentioned above, I've tried these things:

- Removed the front driveshaft and drove with only the rear.
- Removed the rear driveshaft and drove with on the front.
- Swapped the spare tire for either of the rear tires.

With each of these things, the vibration slightly changes, but it doesn't go away. In all the prior posts, I read one where another guy had the vibration and it wasn't related to his front driveshaft, either. He upgraded the bearings in his transfer case, but he was still getting the vibration to some degree, so it didn't resolve it. I was thinking about this while I was supposed to be sleeping last night, and I thought that maybe the driveshaft/transfer case RPMs are just too high, and maybe I'd go to a higher gear ratio, like 4.65 or even back to 4.10's, just go get rid of it. However, Tom Wood's website has a driveshaft RPM calculator, and I found that there is not much difference in driveshaft/TC RPM with a stock Rubicon (30" tires and 4.10 gears) and my Rubicon (35" tires and 4.88 gears). To be exact:

View attachment 412204

As you can see, my Jeep is only turning 40 - 50 RPM higher than a stock Rubicon, so I don't think going to a higher gear ratio would solve anything.

So...I'm at a loss. If anyone has any wisdom, I'd be happy to listen.

What pinion angle adjustments have you tested at the rear driveshaft with the front one removed?

 

[Josh_Br]

The adjustment to -1 degree was fairly recent. If I recall, when I had the front DS out, the rear pinion angle it was lower than -1. I had eyeballed it at that point and it was lower than it should have been/out of spec.

 

[mrblaine]

The adjustment to -1 degree was fairly recent. If I recall, when I had the front DS out, the rear pinion angle it was lower than -1. I had eyeballed it at that point and it was lower than it should have been/out of spec.

The only spec is the angle at which it vibrates the least. Check that.

 

[Josh_Br]

Well, I'm happy to mess with the rear pinion angle some more if you think it will help. However, last weekend I drove the Jeep with only the front driveshaft installed. The rear one was at home, sitting in the garage. Even still, the Jeep vibrated. So that makes me think it's not the rear pinion angle, unless I'm missing something.

 

[mrblaine]

Well, I'm happy to mess with the rear pinion angle some more if you think it will help. However, last weekend I drove the Jeep with only the front driveshaft installed. The rear one was at home, sitting in the garage. Even still, the Jeep vibrated. So that makes me think it's not the rear pinion angle, unless I'm missing something.

Have it your way.

 

[Blackjack]

Well, I'm happy to mess with the rear pinion angle some more if you think it will help. However, last weekend I drove the Jeep with only the front driveshaft installed. The rear one was at home, sitting in the garage. Even still, the Jeep vibrated. So that makes me think it's not the rear pinion angle, unless I'm missing something.

Did you drive it without the front shaft and what was the result? I had a guy with an LJ Rubi that I went round and round with him about driveshafts only for him to finally figure out it was a bad bearing in the Tcase.

 

[Rickyd]

Spin wheels to see if a tire or rim is out of round? Swap tires front to rear?

 

[mrblaine]

Spin wheels to see if a tire or rim is out of round? Swap tires front to rear?

The cyclical pulsation he describes that seems to move from one end of the rig to the other with annoying regularity once you reach a certain speed is very indicative of a driveshaft problem, not with the driveshafts, just with them spinning. The typical steps to start diagnosing are to first ensure there are no bad bearings in the outputs of the t-case, good joints, no lateral play in the slip splines. Once that is verified, then the front shaft is taken out of the equation and the fun with rear pinion angle starts. Start lower, and make small adjustments up until it gets worse or better and keep doing it until you get it vibe free and only then does the front shaft go back in to start adjusting it.

 

[Josh_Br]

Well, I removed the front DS and went for a drive. It still vibrated, but was maybe 25% less severe. I’m haven’t messed with the rear pinion angle, so it should still be at -1 degree.

How can a person diagnose whether transfer case bearings are going bad, or something in that direction?

 

[Good Hope]

Had a similar experience with vibrations. Turned out to be bad tire balance, probably combined with road conditions. The vibration would come and go and seemed to move around. I had the tires rebalanced without any hope of it solving the problem, but it was free, so I started there. And now no vibrations.

 

[Josh_Br]

Thanks, that’s interesting, because I took my tire pressure down to 27 psi (instead of 32) the other day, and it actually improved slightly. Maybe you’re on to something. I hope you are! lol

I’ve got an appointment at a shop this Friday that does tranny and transfer case rebuilds, just to check the Jeep out and see what their thoughts are. I’ll let you all know how it turns out.

 

[JMT]

Well, I removed the front DS and went for a drive. It still vibrated, but was maybe 25% less severe. I’m haven’t messed with the rear pinion angle, so it should still be at -1 degree.

How can a person diagnose whether transfer case bearings are going bad, or something in that direction?

If you’ve run low on diff fluid then you can starve those output shaft bearings. The heat can leave its mark. They should spin really freely. Any stubbornness and the bearing is shot.

 

[Josh_Br]

If you’ve run low on diff fluid then you can starve those output shaft bearings. The heat can leave its mark. They should spin really freely. Any stubbornness and the bearing is shot.

Thanks, that makes sense. I appreciate it. I’ll check that out.

 

[Josh_Br]

Well, I had some extra time before work this morning, so I took the Jeep in to have the tires rebalanced, just in case that was the problem. Now let me say that I've had tires out of balance in the past on other vehicles, and I'd describe the feeling more as a wobble than a vibration, or even a high-speed wobble. The problem I've been having currently with the Jeep has been more of a vibration or pulsation. Plus, the tires only have 1500 miles on them, so I really didn't suspect them being a problem. Anyhow, after getting the tires re-balanced this morning, the vibration is 99% gone. I also still have only 26.5 PSI in each tire. I'll probably continue to mess around with the PSI some, but otherwise, I think this is resolved. In case it's relevant to anyone else, the tires are Yokohama Geolandar MT G003's. They're 10 ply, which perhaps has something to do with all of this (being extra stiff). If anyone has any additional thoughts, I'd be happy to hear them. Otherwise, thanks for helping me think and get to the bottom of this!

 

[Good Hope]

Well, I had some extra time before work this morning, so I took the Jeep in to have the tires rebalanced, just in case that was the problem. Now let me say that I've had tires out of balance in the past on other vehicles, and I'd describe the feeling more as a wobble than a vibration, or even a high-speed wobble. The problem I've been having currently with the Jeep has been more of a vibration or pulsation. Plus, the tires only have 1500 miles on them, so I really didn't suspect them being a problem. Anyhow, after getting the tires re-balanced this morning, the vibration is 99% gone. I also still have only 26.5 PSI in each tire. I'll probably continue to mess around with the PSI some, but otherwise, I think this is resolved. In case it's relevant to anyone else, the tires are Yokohama Geolandar MT G003's. They're 10 ply, which perhaps has something to do with all of this (being extra stiff). If anyone has any additional thoughts, I'd be happy to hear them. Otherwise, thanks for helping me think and get to the bottom of this!

Glad it turned out to be a simple, inexpensive fix!