Ask The Expert- Vibration

Steve E

Jeep Newb
'15 JK 4 dr. Just changed stock ring/pinion to 4.56. Now getting a vibration from front at 44mph and rear vibration at 55. Fades as I drive faster. We changed the drive shaft and rebalanced it. Checked the usual but still have the issue. Solutions? Issue? Help.
 

Steve E

Jeep Newb
This is a mild lift and suspension for an old timer. Its 2.5 lift. Dana 30 4.56. Basic Fox shocks, 35s.Dont know pinion angle but can ask the installer
 

Cloaked Willys

Jeep Fanatic
Yeah, It sounds like the angles are off somewhere. You might need to add adjustable control arms to make the needed adjustments if you do not already have some.
 

Brian

Jeep Fanatic
Yeah, It sounds like the angles are off somewhere. You might need to add adjustable control arms to make the needed adjustments if you do not already have some.
I trust you 100%, I want to add to his question. If he does not have adjustable control arm in the front..... he is most likely not running a lot of caster..... Unlike a Gamechanger 3.5", where you can run 5.5 degrees of caster....( but that puts more stress on the front drive line angles.

Doesn't the front vibration sort of say that maybe the gears that were just installed might be out?

Does the vibration go away under throttle and stop while coasting? Is there a whine at all on coasting?

What driveshafts were installed and why U joints are in them? Are they greased?
 

Steve E

Jeep Newb
Only did a 2,5" lift. Vibes hit at 45, really kick in at 60 and 70, continuous. Coast down is stronger. When throttling under a load you dont feel it till you coast at these speeds. Stock axles.
 

timatoe

Jeep Fanatic
I'd lean toward angles as well, if it were just gearing that was done, I'd look there first. You could pull the front drive shaft and see if you're still getting vibes, if so pull the rear and check again. Then you've effectively cut the Jeep in half and know whether it's front or back.
 

Steve E

Jeep Newb
Vibration Issue revisit

Tx all, It goes back in the shop Mon and will ask these questions. Appreciate the input.
So we tried changing gear set several times and doing all the usual fixes to no avail. Last thing we just did was to change 4.56 to 4.10 and no problem. Explanation I gpt is something to do with the transmission I have. Its the stock unit that came with my '15 JK so not sure whats up with this but now vibrationless?!?!?
 

Brian

Jeep Fanatic
So we tried changing gear set several times and doing all the usual fixes to no avail. Last thing we just did was to change 4.56 to 4.10 and no problem. Explanation I gpt is something to do with the transmission I have. Its the stock unit that came with my '15 JK so not sure whats up with this but now vibrationless?!?!?
I guess congrats... but that sort of sucks.
 

Pthorpe84

Moderator
Staff member
Could it not have something to do with the drive shaft RPM's causing the vibration with the deeper gears? I.e. Out of balance


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Pthorpe84

Moderator
Staff member
Seen this a few times. It just happens to find that sweet spot that it doesn't like.
Yep. Very similar to death wobble when your tires are out of balance. I know that the drive from my house to rock your 4x4, my jeep would shake violently at the 37-45 mph range. Then stop at speeds above that. Once balanced....no more shake.


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Todd Ockert

Moderator
Could it not have something to do with the drive shaft RPM's causing the vibration with the deeper gears? I.e. Out of balance


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This was my guess was an issue with the drive shaft and the higher revolutions of it with the deeper gears.

If you really want the 4.56 gears, you also might look at getting a good drive shaft shop, like Tom Woods to make a new shaft for you.
I have a local shop that will do high speed balancing of the shafts.

Todd
 
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