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

I also found this - see the part about u-joint indexing.

Can one of you folks try this? @Ranger_b0b? Still think there is merit to this idea, but not sure if this is applicable for us completely.

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jodomcfrodo said:
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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My vibrations do not go away after removing the Front driveshaft. They reduced in intensity after rebuild+rebalance but after that there is no difference with or without the front DS.
 
So from what I am reading the phasing didn't fix the issue the driveline did correct? I mean if the driveline shop wouldn't have phased it wrong it would have been fixed correct?
 
psrivats said:
@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.
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I wasn't aware of this. I thought yours was coming from the front. So that means your vibration isn't coming from the front then, and it has to be coming from the rear. I say that because if it makes no difference in vibration whether the front shaft is removed or not, that obviously points to the rear being the only culprit.
 
psrivats said:
My vibrations do not go away after removing the Front driveshaft. They reduced in intensity after rebuild+rebalance but after that there is no difference with or without the front DS.
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Just put manual hubs on the rear axle then! Duh...

In all seriousness, I'm not quite sure what your problem has been. Have you removed the rear driveshaft and driven around in front wheel drive to see if that does anything? I'm hoping I don't end up with these vibrations after my Savvy TT install...
 
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jodomcfrodo said:
Just put manual hubs on the rear axle then! Duh...

In all seriousness, I'm not quite sure what your problem has been. Have you removed the rear driveshaft and driven around in front wheel drive to see if that does anything? I'm hoping I don't end up with these vibrations after my Savvy TT install...
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I regeared from 4.10-->4.88. No vibration before but developed after the regear. Jeep is with Dave (who did the regear) and he has has the front driveshaft rebuit+rebalanced. Vibrations reduced somehwat but did not go away (it is still pretty severe, starts at 60mph and increases with speed). Now, after the front DS rebuild, the vibrations are the same with or without the front driveshaft in place. Jeep is still with Dave who is dignosing the issue. Not sure if he has removed the rear DS and tried running in front wheel drive only, but I expect he has checked the entire driveline thoroughly already based on what he told me. In my case atleast, he mentioned manual hubs on the fronts won't help.
 
So originally I wanted to be added to this group, but I don't think I can now. I think I made too many changes to decide what is new and what is causing what. I mean I didn't do them all at the exact same time, but not really enough apart to tell for sure what is causing what. Driving in today I payed really close attention and I have a minor, minor vibration I think starts at around 50 although my speedometer is way off so I don't know the actual speed. I am guessing about 10 mph slower in reality. But it could really be the aggressive tires honestly. But at higher speeds i get a little more slight vibration under load. Still nothing to barely even mention. It could be that I just need to dial in my pinion angles abit. I know my front is low trying to fix a caster issue I have been having. I really need to just spend more time on the suspension before I start blaming drivelines in my case. So I will watch this thread with anticipation, but I don't think I can offer and constructive advice in this case. I do hope you guys figure it out though in case once I get everything dialed in I get that issue.

Good Luck.
 
psrivats said:
I also found this - see the part about u-joint indexing.

Can one of you folks try this? @Ranger_b0b? Still think there is merit to this idea, but not sure if this is applicable for us completely.

View attachment 59494
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You wouldn't want to do this. They are talking about steering here, which is low speed (VERY low speed). If you operated a driveshaft at a severe enough angle that you were getting "hard spots" in it, it would self destruct in short order. Those hard spots are where the yoke ears are starting to interfere with each other!
 
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Ranger_b0b said:
You wouldn't want to do this. They are talking about steering here, which is low speed (VERY low speed). If you operated a driveshaft at a severe enough angle that you were getting "hard spots" in it, it would self destruct in short order. Those hard spots are where the yoke ears are starting to interfere with each other!
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Ah ok. Makes sense. I'll keep reading and see if there is anyone out there who has had this problem resolved, ever.

Even the JK guys are talking about this issue a lot, btw. So many threads on other forums ...
 
There has been a similar issue with I believe Toyota Tundra’s and the solution was to actually put the drive shaft joints out of phase and it corrected it. I never had the balls to try it on the Jeep to see if it helped. I highly doubt it would.
 
jeepndogs said:
There has been a similar issue with I believe Toyota Tundra’s and the solution was to actually put the drive shaft joints out of phase and it corrected it. I never had the balls to try it on the Jeep to see if it helped. I highly doubt it would.
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How much out of phase I wonder? One spline, two, 180 out?
 
jeepndogs said:
It was surprisingly 180 out. If I remember correctly it was actually a factory recommendation. I will have to see if I can find the information again.
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I might be stupid enough to try something like that. Wouldn't that be amazing if it cured the vibes?
 
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@bobthetj03 @jeepndogs please post the link if you find it. I am VERY curious.

My thinking now is that there is a vibration from the driveshaft or the u-joints that sets up a resonant vibration in the frame/body even if they are OK individually. Adding dampening material between TC skid and frame may help make the resonation go away since it will change the mass and therefore the rpm at which the frequency happens. I have been chatting with @Chris about this as well.

@Chris this sounds very plausible now on top of what Dave said, no?
 
psrivats said:
@bobthetj03 @jeepndogs please post the link if you find it. I am VERY curious.

My thinking now is that there is a vibration from the driveshaft or the u-joints that sets up a resonant vibration in the frame/body even if they are OK individually. Adding dampening material between TC skid and frame may help make the resonation go away since it will change the mass and therefore the rpm at which the frequency happens. I have been chatting with @Chris about this as well.

@Chris this sounds very plausible now on top of what Dave said, no?
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That may be, but you don't want to run a DS that is vibrating. It will ruin your U-joints eventually...So..you may be able to mask the problem with some sort of damping material, but its not the solution you want to do.
 
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