4.0, 42RLE, NP241OR High Speed Vibrations After Re-Gear to 4.88 or Deeper
- Thread starter Mr. Bills
- Start date
To find your driveshaft rpm, determine which transmission gear is direct drive(1:1 ratio) So for a 5 speed it would be 4th. With an auto, it would be drive, OD off and torque converter locked. So running down the road in direct drive, simply read your tachometer and that IS your driveshaft rpm, plain and simple.
When driveshafts are balanced, they are spun in a straight line on a machine. When they are in our jeeps, they obviously don't rotate on a level plane. This is where wear, tolerances and operating past max specs come into play. Like a previous poster stated, the CV joint on the front driveshaft was good to 13 degrees at 5000 rpm, but a lift kit then placed the CV joint at 15 degrees of angle. If you are driving down the road and hit bumps compressing your suspension, that angle changes.
How many miles are on these Jeeps that have vibration? The Rubicon I own/drive has 156k miles on it, the front driveshaft has rotated every mile of that 156k because of the lack of hubs, and I have yet to find a single grease zerk on it to service, which is frustrating. So some of you will have worn CV joints, and wear/slack in the slip yoke splined portion of the driveshaft. Lack of grease also causes flat spots on the needle rollers of the u-joints in the driveshaft, all of which leads to binding, causing vibrations.
And for the record, the driveshaft is NOT spinning any faster than it was when stock, if the tire size and axle ratio is matched to one another when changed. In other words, at 60 mph, the only way you could get your driveshafts to spin FASTER after lifting your Jeep, changing the axle ratio, and adding the appropriate larger diameter tire size to match the gears, is to REMOVE the larger tires and go back to the smaller diameter original stock tires. Ground speed would still be 60 mph, but the smaller diameter tires would have to rotate faster to be at 60 mph, and thus the driveshaft and engine would have to operate at a higher rpm than before to achieve 60 mph.
When driveshafts are balanced, they are spun in a straight line on a machine. When they are in our jeeps, they obviously don't rotate on a level plane. This is where wear, tolerances and operating past max specs come into play. Like a previous poster stated, the CV joint on the front driveshaft was good to 13 degrees at 5000 rpm, but a lift kit then placed the CV joint at 15 degrees of angle. If you are driving down the road and hit bumps compressing your suspension, that angle changes.
How many miles are on these Jeeps that have vibration? The Rubicon I own/drive has 156k miles on it, the front driveshaft has rotated every mile of that 156k because of the lack of hubs, and I have yet to find a single grease zerk on it to service, which is frustrating. So some of you will have worn CV joints, and wear/slack in the slip yoke splined portion of the driveshaft. Lack of grease also causes flat spots on the needle rollers of the u-joints in the driveshaft, all of which leads to binding, causing vibrations.
And for the record, the driveshaft is NOT spinning any faster than it was when stock, if the tire size and axle ratio is matched to one another when changed. In other words, at 60 mph, the only way you could get your driveshafts to spin FASTER after lifting your Jeep, changing the axle ratio, and adding the appropriate larger diameter tire size to match the gears, is to REMOVE the larger tires and go back to the smaller diameter original stock tires. Ground speed would still be 60 mph, but the smaller diameter tires would have to rotate faster to be at 60 mph, and thus the driveshaft and engine would have to operate at a higher rpm than before to achieve 60 mph.
jeepndogs
TJ Enthusiast
I agree with most of your points. It is important to keep in mind that the driveshaft is spinning faster than stock and at an increased angle. The appropriate gear ratio is not just
(new tire * old gear)
—————————
(Old tire)
Using that method would result in a 4.62 gear ratio for a rubicon with 35’s. Obviously, you don’t run 4.56’s with 35’s, especially on a 42RLE. Most jeeps are simply undergeared from the factory, especially the 4 speeds. With 5.38’s and 35’s, Chris’s drive shaft is spinning 16% faster than stock and at a much larger angle because of his 4” suspension lift and because of his TT.
And for the purposes of this discussion based on Chris’s post, it is spinning much faster than when he had 4.10’s as nothing changed in terms of tire size.
Ultimately that’s what I may end up doing if Dave doesn’t solve it. There’s just some confusion as to whether I would need new RCV axles or not since most of these manual hub kits include new (longer) outer shafts.
I brought all of this to Dave's attention, including the point @Ranger_b0b had brought up about the driveshaft thickness. We'll see if he has any input on it.
I refuse to just accept this as a problem without a solution. There is a solution, it looks like we just have to collectively figure out what the solution is.
I refuse to just accept this as a problem without a solution. There is a solution, it looks like we just have to collectively figure out what the solution is.
Also, here's another one @psrivats found on Jeep Forum with a solution:
I had my 03 sport regeared in the spring from 3.73 to 4.56. At the time, had 2.5" RC lift with 3/4 spacers, 1"TC drop. Before the regear everything ran great. After the regear I had a slight vibration when going over 90kph.
Series of events:
Pulled the front ds, vibe free... ok time to take my ds to be rebalanced at (what I thought as a fairly reputible Driveline shop, read specialty shop)
Ended up having ujoints replaced, ball/cup relubed, and the shaft rebalanced to 2250rpm (standard for them apparently, even though I specified with my gearing and tire sizes I'm WELL over that, ~3000rpm range). $350 later, With the ds installed...
Still vibed.
One shop blamed my old tires, layers seperating etc. Took this opportunity to buy new 33x12.5 duractracs, balanced etc.
Still vibed.
1Month passed:
Took the DS back for warrenty rebalance, they pulled the weights off and put new ones on free of charge.
Still vibed.
2 Months passed:
Ok must be pinion angle, purchased IRO adjustable uppers and lowers. Had a (different) shop do a full 4 wheel alignment. and adjusted the driveline a bit more after I put the arms in, although I was pretty close apparently.
Still vibed.
Add, adjustable trackbar, MML, ditched the TC drop, a few other mods, just things I had been wanting to do, no change after installation.
Still vibed.
5 Months Passed:
Replaced both Hubs/Unit bearings, and axle ujoints, it would be an understatement to say the ujoints really needed replacing anyways,
Still vibed.
Took my jeep to the Driveline shop, the parts and service managers took my jeep for a ride with and without the front ds, said it's definitly front ds related, they recommended retubing it, and a full rebalance and they'd do me a favor and only charge me $650 to get it done. Ok fine, if it will fix the issue once and for all I'll be happy. I took it for it's maiden voyage with the service manager in the passenger seat...
Still vibed. (At least I got a free DS out of it
)
Decided I'd cave and it must be a bad bearing out of the factory, or a faulty gear install. Took it to one of my clubs favorite/trusted 4x4 shops, the old shop isn't around anymore, but the mechanic who did the gear install in the first place has moved to this new shop. I paid for a bearing replacement kit + install. the Shop owner did a lot of the work with the mechanic since they genually wanted this issue to be fixed.
They took apart the front diff, the gear wear pattern was excellent but the bearings were oddly worn, and the races were scored/pitted. They seemed releaved with the initial idea that the bearings were bad out of the factory. They installed the new races/bearings, buttoned it up. Took it for a drive.
Still vibed.
Next step, the shop put it on the lift set cruise control to 130kph, and could see the ds vibing. Set a dial indicator to it, 0.060" movement. Pulled the ds, went to set it down, hey look it doesn't sit right, it "wobbled". Dave looked at it, saw immediatly that the ujoints were out of phase, pulled the slip joint apart, adjusted it two notches. reinstalled.
No Vibes
*I finally enjoy taking the jeep on the highway again*
So special thanks to Dave, and Eric @ BrokenAxle
So my question: what should I do about the driveline shop I went to in the first place? I mean to have a shaft, rebuild it once, rebalance it a second time, and finally retube it, how could they not notice it was out of phase?
Part of me wants to mention it to them as a warning that "hey your guys arn't looking at these shafts very well". Oh and when I asked to have the ds balanced at 3000rpm or above they looked at me weird, looked at the jeep weird, and said no you don't need it that fast, muscle cars do, jeeps don't... ok. So I went home did math, when I picked up the ds, I showed them my calcs, they told me my math was wrong, and to go install this free ds and my vibes would be fixed. (I'm a Profesionally registered Mechanical Engineer, I'd really like to think my math isn't generally just flat out "wrong")
Thanks for the read, hoepfully it helps someone out. Let me know your thoughts.
Series of events:
Pulled the front ds, vibe free... ok time to take my ds to be rebalanced at (what I thought as a fairly reputible Driveline shop, read specialty shop)
Ended up having ujoints replaced, ball/cup relubed, and the shaft rebalanced to 2250rpm (standard for them apparently, even though I specified with my gearing and tire sizes I'm WELL over that, ~3000rpm range). $350 later, With the ds installed...
Still vibed.
One shop blamed my old tires, layers seperating etc. Took this opportunity to buy new 33x12.5 duractracs, balanced etc.
Still vibed.
1Month passed:
Took the DS back for warrenty rebalance, they pulled the weights off and put new ones on free of charge.
Still vibed.
2 Months passed:
Ok must be pinion angle, purchased IRO adjustable uppers and lowers. Had a (different) shop do a full 4 wheel alignment. and adjusted the driveline a bit more after I put the arms in, although I was pretty close apparently.
Still vibed.
Add, adjustable trackbar, MML, ditched the TC drop, a few other mods, just things I had been wanting to do, no change after installation.
Still vibed.
5 Months Passed:
Replaced both Hubs/Unit bearings, and axle ujoints, it would be an understatement to say the ujoints really needed replacing anyways,
Still vibed.
Took my jeep to the Driveline shop, the parts and service managers took my jeep for a ride with and without the front ds, said it's definitly front ds related, they recommended retubing it, and a full rebalance and they'd do me a favor and only charge me $650 to get it done. Ok fine, if it will fix the issue once and for all I'll be happy. I took it for it's maiden voyage with the service manager in the passenger seat...
Still vibed. (At least I got a free DS out of it
)Decided I'd cave and it must be a bad bearing out of the factory, or a faulty gear install. Took it to one of my clubs favorite/trusted 4x4 shops, the old shop isn't around anymore, but the mechanic who did the gear install in the first place has moved to this new shop. I paid for a bearing replacement kit + install. the Shop owner did a lot of the work with the mechanic since they genually wanted this issue to be fixed.
They took apart the front diff, the gear wear pattern was excellent but the bearings were oddly worn, and the races were scored/pitted. They seemed releaved with the initial idea that the bearings were bad out of the factory. They installed the new races/bearings, buttoned it up. Took it for a drive.
Still vibed.
Next step, the shop put it on the lift set cruise control to 130kph, and could see the ds vibing. Set a dial indicator to it, 0.060" movement. Pulled the ds, went to set it down, hey look it doesn't sit right, it "wobbled". Dave looked at it, saw immediatly that the ujoints were out of phase, pulled the slip joint apart, adjusted it two notches. reinstalled.
No Vibes
*I finally enjoy taking the jeep on the highway again*
So special thanks to Dave, and Eric @ BrokenAxle
So my question: what should I do about the driveline shop I went to in the first place? I mean to have a shaft, rebuild it once, rebalance it a second time, and finally retube it, how could they not notice it was out of phase?
Part of me wants to mention it to them as a warning that "hey your guys arn't looking at these shafts very well". Oh and when I asked to have the ds balanced at 3000rpm or above they looked at me weird, looked at the jeep weird, and said no you don't need it that fast, muscle cars do, jeeps don't... ok. So I went home did math, when I picked up the ds, I showed them my calcs, they told me my math was wrong, and to go install this free ds and my vibes would be fixed. (I'm a Profesionally registered Mechanical Engineer, I'd really like to think my math isn't generally just flat out "wrong")
Thanks for the read, hoepfully it helps someone out. Let me know your thoughts.
Also, here's another one @psrivats found on Jeep Forum with a solution:
I had my 03 sport regeared in the spring from 3.73 to 4.56. At the time, had 2.5" RC lift with 3/4 spacers, 1"TC drop. Before the regear everything ran great. After the regear I had a slight vibration when going over 90kph.
Series of events:
Pulled the front ds, vibe free... ok time to take my ds to be rebalanced at (what I thought as a fairly reputible Driveline shop, read specialty shop)
Ended up having ujoints replaced, ball/cup relubed, and the shaft rebalanced to 2250rpm (standard for them apparently, even though I specified with my gearing and tire sizes I'm WELL over that, ~3000rpm range). $350 later, With the ds installed...
Still vibed.
One shop blamed my old tires, layers seperating etc. Took this opportunity to buy new 33x12.5 duractracs, balanced etc.
Still vibed.
1Month passed:
Took the DS back for warrenty rebalance, they pulled the weights off and put new ones on free of charge.
Still vibed.
2 Months passed:
Ok must be pinion angle, purchased IRO adjustable uppers and lowers. Had a (different) shop do a full 4 wheel alignment. and adjusted the driveline a bit more after I put the arms in, although I was pretty close apparently.
Still vibed.
Add, adjustable trackbar, MML, ditched the TC drop, a few other mods, just things I had been wanting to do, no change after installation.
Still vibed.
5 Months Passed:
Replaced both Hubs/Unit bearings, and axle ujoints, it would be an understatement to say the ujoints really needed replacing anyways,
Still vibed.
Took my jeep to the Driveline shop, the parts and service managers took my jeep for a ride with and without the front ds, said it's definitly front ds related, they recommended retubing it, and a full rebalance and they'd do me a favor and only charge me $650 to get it done. Ok fine, if it will fix the issue once and for all I'll be happy. I took it for it's maiden voyage with the service manager in the passenger seat...
Still vibed. (At least I got a free DS out of it
Decided I'd cave and it must be a bad bearing out of the factory, or a faulty gear install. Took it to one of my clubs favorite/trusted 4x4 shops, the old shop isn't around anymore, but the mechanic who did the gear install in the first place has moved to this new shop. I paid for a bearing replacement kit + install. the Shop owner did a lot of the work with the mechanic since they genually wanted this issue to be fixed.
They took apart the front diff, the gear wear pattern was excellent but the bearings were oddly worn, and the races were scored/pitted. They seemed releaved with the initial idea that the bearings were bad out of the factory. They installed the new races/bearings, buttoned it up. Took it for a drive.
Still vibed.
Next step, the shop put it on the lift set cruise control to 130kph, and could see the ds vibing. Set a dial indicator to it, 0.060" movement. Pulled the ds, went to set it down, hey look it doesn't sit right, it "wobbled". Dave looked at it, saw immediatly that the ujoints were out of phase, pulled the slip joint apart, adjusted it two notches. reinstalled.
No Vibes View attachment 59469
*I finally enjoy taking the jeep on the highway again*
So special thanks to Dave, and Eric @ BrokenAxle
So my question: what should I do about the driveline shop I went to in the first place? I mean to have a shaft, rebuild it once, rebalance it a second time, and finally retube it, how could they not notice it was out of phase?
Part of me wants to mention it to them as a warning that "hey your guys arn't looking at these shafts very well". Oh and when I asked to have the ds balanced at 3000rpm or above they looked at me weird, looked at the jeep weird, and said no you don't need it that fast, muscle cars do, jeeps don't... ok. So I went home did math, when I picked up the ds, I showed them my calcs, they told me my math was wrong, and to go install this free ds and my vibes would be fixed. (I'm a Profesionally registered Mechanical Engineer, I'd really like to think my math isn't generally just flat out "wrong")
Thanks for the read, hoepfully it helps someone out. Let me know your thoughts.
I’d have a hard time believing all the multiple driveshafts people have tried are just out of phase, or would the angle mess up the phasing? Hopefully it’s that simple
Thanks @Chris for sharing that. I've been reading thread after thread on other forums as well to see if anyone found a solution.
To follow up on the above post, this is what they had to say about the ujoints. Can one of you guys check this theory out?
To follow up on the above post, this is what they had to say about the ujoints. Can one of you guys check this theory out?
- hey what is "out of phase" ujoints? Thx
edit: I think I might be able to guess at it, but am still curious to know for sure
The u joints should line up if u were to look down the ds across the caps..if out of phase the caps are offset from each other...hard for me to explain hope u understood that or someone will do a better job at it
My front DS CANNOT be assembled out of phase (at least on the splines). When I pulled it apart, I made sure to remember to mark it. Once I got it cleaned up though, I noticed there is a section in the female side that is missing a "tooth" so it creates a double wide slot. There is also a weld on the male side, so that it can ONLY go together one way. That is a perfect example of a factory Poke-Yoke...so you guys with factory DS that are having vibes, I would assume that it is not an out of phase condition.
Yes...that is correct. The U-joints have to be "in Phase" because as they rotate, they are rotating in an Elliptical motion due to the angle of operation. Since they are elliptical, there is some angular acceleration happening at each cap or bearing. A correct Driveshaft phase means that the upper joints acceleration will be equal and opposite the lower joints acceleration, thereby canceling one another. If they get out of phase, they won't cancel each other out and will introduce vibs.
Note: this is also why it is important for your U-joint angles to be the same top and bottom. Same principle at work.
Thanks. I've been reading a lot and I thought that sounded like a possible thing so thought I would share it.
I also found this video that is pretty interesting.
@Chris In my Jeep, Dave said after the driveshaft rebuild+rebalance, the jeep has the same vibration with or without the front driveshaft in place (although vibrations reduced somewhat after the rebuild). When I asked about locking hubs, Dave said it won't make a difference. The fact that there are jeeps where the problem completely disappears with manual locking hubs tells me that this problem has multiple sources and it is hard to figure out what is acting out of spec. Front drive shaft seems to be only one part of it and there is no guarantee that locking hubs will fix the problem.
I'm confused. How would manual hubs not fix this? If you remove the front driveshaft, the vibes go away, right? Adding manual hubs would basically do the same thing as removing the front driveshaft. Did he offer any reasoning behind manual hubs not doing anything?
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