Vibration After Gear Change....HELP !!!!!

[SandCuda]

I have a 2014 JKU Sport with 31,000 miles on the clock running a 2.5 AEV lift that was installed in June 2014. Last month I had a shop do a 4.56 gear up grade from the stock 3.73's to improve performance in the mountains and pulling my teardrop. Since the gear change I have had a pulsing vibration that starts about 55 mph and gets worse as speed increases. (NO VIBES BEFORE GEAR CHANGE) New front drive shaft has been installed along with new front transfer case bearing and I still have the vibes. Also tires are not the cause as I installed new Cooper AT3's 285/70R/17's last week with zero change in the vibration from the old tires.
Looking for help, guidence, solutions, and suggestions from those that have been down this path. NOTE: The shop that did the gear change does about 400 gear changes a year and they now appear to be stumped about the cause of the vibration.

 

[expedition4x4]

Remove front drive shaft and see if the vibes go away, these kinds of things need a methodical isolation of potential gremlins? I would start with the new shaft.

 

[FastGlass]

I'd second pulling the shaft and seeing if the vibration persists. A 2.5 lift by itself isn't too steep, but remember, those AEV lifts are designed to give stated lifts with heavier bumpers, winches etc...
With none of that(?) your actual lift could be closer to 3.5" or more. That IS getting steep for the DS and maybe the pinion/castor angle is causing driveline stress. Does the 2.5" AEV use geometry correction brackets? I dunno. If not, your DS angle to the transfer case could be really steep if not corrected with brackets/adj. arms. Might not notice it too bad right away, but...
Pull the DS and see...it's easy to do and you'll know for sure if it's that, or something more severe.

 

[Martyn]

I don't believe that the AEV 2.5" lift would have any adverse effect on the drive shaft. Geometry correction brackets are not required for the lift but can be added. Never see an issue like this with any of the AEV lifts AT has done. From the original post it sounds like the lift was done well before the re-gearing and the issue came after re-gearing. I'd be looking at everything done during re-gearing and try to methodically isolate the problem.

 

[SandCuda]

The jeep did a 9,250 mile 6 week cross country overland trip without a single vibration issue after the lift installation. A lot of paved driving was done at 75 MPH for long distances in the mid west. My vibration issues started after the gear change. Per my calculations it looks like the DS, RPM's at 75MPH with old gears and the DS, RPM's at 60MPH with new gears are almost identical. However I never experienced any type of vibration prior to the gear install.

 

[shortbus4x4]

Did the shop get all the drive lines back in their correct places, not out of phase? Pull front drive line and see if it goes away. Then put front back in and pull rear.

 

[gohuge]

Need to test drivelines first. ^^^What he said^^^

 

[rubicon91]

Excuse my extremely novice comments here but I just did a regear on my 12 from 321 to 456 and I had a break in period where one stop was 100 miles then at 500 another for towing purposes. That was from Yukon. I have Yukon gears. Did you have to do any break in of your new gears? Outside of that I have no clue. I babied mine for the 500 and love the new gears. This probably has zero to do with your issue but thought I would throw it out.

 

[expedition4x4]

There is a break in but this definitely sounds more like a front driveshaft issue

 

[jeep-N-montero]

One thing to keep in mind is the drive shafts are now turning more revolutions per minute than before due to the new gearing. I know on my old Jeep I would get seemingly more vibration when running the 33 inch winter tires than the 35 inch summer tires with the same 4.56 gearing, this was due to the drive shafts turning at a higher rate with the smaller tires at a higher rotation than the larger tires at a lower rotation at a given speed. Changing gearing or tire size has the same effect on the drive shafts and will vary the rotation speed of the shaft, thus changing the harmonics and/or vibration as well as your cruising rpm. I simply learned to live with it.

 

[SandCuda]

Jeep was babied a lot during the 500 mile break in period. Was not driven over 50 MPH. Was only driven 28 miles to get home after the install. Never driven more than 30 miles at a time during break in period. Never fast on the gas. The same shop did the oil changes after the 500 mile break in period. The shop will pull covers and check all settings and adjustments next week to confirm a proper installation. Prior to checking the install we will pull the front DS to see if we have a change in vibration in an effort to isolate the problem

 

[uwrfgus]

Experiencing a similar issue...did you get resolved and what ended up being the culprit?

 

[SandCuda]

Yes...Bad gear job. Had another shop due a second gear conversion. Replaced the after market drive shafts the first shop convinced me to buy to solve the vibration and noise problem with new factory shafts. Problem solved with thousands of dollars. Sold "Heep" due to many other Jeep related (electrical & trans) issues. Now have a Tacoma, a much more reliable and dependable truck.