Re-geared, now I have a vibration above 50 mph
- Thread starter bobthetj03
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White Shadow 99
Member
Hey Rob, small world. What side of the tracks are you on? LJ your color just drove by my house last night.
Southport. I have seen that LJ. There are a few in town that I have seen. A real nice red TJ as well.
White Shadow 99
Member
Southport as well, you’ve got my phone number now. I wheel just as much in the snow as the dirt.
White Shadow 99
Member
So to provide more detail over the last year I built a new 06 LJ and as soon as I regeared I had vibration issues as well. I went back through and made sure that all the control arms were the same length, the axles were perpendicular to the frame and made sure track bars are within 16th of an inch on center at ride height and played with pinion angles many times. I pulled the front driveshaft and no change so I knew it was isolated to the rear. Lifted up vehicle from axles and checked run out of driveshaft. I also habe an Adams rear driveshaft and he also sent me out a replacement and while it was a little bit better still have vibration. Best angle I found was about a half a degree less than the driveshaft. Changing the transfer case mount helped as well even though the original one looked fine. Before it would come on about 50 miles an hour now it comes on about 65 miles an hour so heading in the right direction. Also have had the new wheels and new tires rebalanced twice and the last time they called it a load force balance that’s where they actually put a rolling drum on the top of the tire and counterbalance based on high spots as well. No change after the load force balance. I have an advance adapter SYE and a UCF skid plate/tummy tuck. The skid plate is not flat to the frame but still an inch and a half or so higher than stock. Ball joints are good and new Currie correctlink steering. Of course it’s a LJ with a longer drive shaft so I shouldn’t even have this problem as my 99 TJ with a 4” Lift can drive 80 without vibration. I have not looked at specific run out on the yolks as I’ve read earlier in this thread I’m really hoping it’s not the advanced adapter because then I would have took my transfer case apart a third time as the first time I installed it it leaked for some reason so I used an ungodly amount of RTV the second time. Actually I take that back I would be willing to take apart a 3rd time to get rid of this damn vibration any other thoughts on your vibration challenges? I would say mine is now livable but with all the money and time invested and the fact that I like to solve problems not live with them I’m still searching.
OP
I've done pretty much same as you sans changing the trany mount. Been thru 2 new front drive shafts, and now 2 new rear drive shafts. Pinion angle changes till I'm blue in the face. I gave up and left the rear pinion angle at 0.5* lower than the drive shaft, like you. Mine come on at 50 mph. Worse at 65, and I don't even want to do 70 anymore. I even checked runout of both rear yokes and have very minimal run out. Pinion angle in the front is within 1.4* of the drive shaft. Gonna start over cause it's going on 2 years now with this effing vibes, so gonna replace the trany mount, pull the front drive shaft, check the torque of the front yoke and input yoke on the TC, then drive it to see if I can focus on eliminating the rear drive shaft vibes. I feel like the front and rear drive shafts are working against each other to cause these vibes. I've already pulled the rear drive shaft and drove around for a while, and the vibes are very minimal. If I can get it to that stage with both drive shafts hooked up , I could probably live with it.
White Shadow 99
Member
The one thing I didn’t mention it is at 55 to 65 I can shift from two high to four high back to two high and absolutely no change in vibration. Bob if you’re ever in town we should get together and drive each other‘s rigs perhaps two heads are better than one and we can help solve each other‘s problems but I would definitely do the tranny mount it’s pretty quick it’s half an hour job if you got a Jack, a block of wood for the tranny, 18mm and 13mm. It reduces the overall drone as well as the pulsating drone sound, now it’s more of a reduced steady vibration/sound that you spoke of earlier in one of your post.
OP
Yep, we should do that. Changing the trany mount today. Will report back with my results. Crazy that you are having these vibes with your jeep being an LJ. Who did your re gear?
jeepndogs
TJ Enthusiast
OP
Changed the trany mount, removed the front drive shaft, Checked torque on front diff yoke and TC input yoke. While I was under there, I also re-re-checked all the control arm bolts. Everything was tight. Drive home netted same vibes, but less pronounced, which I kind of expected being that there's no front drive line spinning. At 55 mph, I still get a harmonic wave vibe that is more heard than felt. At 65, the harmonic smooths out, but the felt vibes picks up. Not felt as much in the seat or steering wheel, but still there. The shifter doesn't bounce around as much, so I guess changing the trany mount didn't hurt. I'll drive it around this week without the front drive shaft and mess with the pinion angles some more. Won't help, but I'm out of ideas, other than something amiss in the rear end or a bent Advanced Adaptors rear output shaft?
OP
So, the past few days have been spent playing with rear pinion angles and going for drives. Started off at 0*, then 0.5* lower, then 1.0* lower, then 1.5* lower. I then went batshit crazy and took it the other direction to 0.5* higher than the drive shaft just for shits and giggles. The harmonic seemed to be the least annoying at 0.5* lower, so I put it back to that setting. It's still not great, but at least now I can move on. The vibes are now a low pitch roar that pulses and seems the most severe at 55 mph.
Next up, I'll reinstall the front drive shaft, remove the rear, and check the rear yokes torque and make sure they are both tight. The new trany mount did nothing but make the shifter not bounce around as much as it used to. When I measured the front pinion angle, I was 1.4* off, so I might try to get that closer.
New trany mount cause pics.
Checking torque on rear yokes. Sorry for the blurry pic. Tough holding the breaker bar, torque wrench and phone.
Next up, I'll reinstall the front drive shaft, remove the rear, and check the rear yokes torque and make sure they are both tight. The new trany mount did nothing but make the shifter not bounce around as much as it used to. When I measured the front pinion angle, I was 1.4* off, so I might try to get that closer.
New trany mount cause pics.
Checking torque on rear yokes. Sorry for the blurry pic. Tough holding the breaker bar, torque wrench and phone.
I guess all you can do now is trade tires with the guy in Sacramento and get the pattern in the differentials checked. Maybe you two can figure it out. Shouldn't be doing that. Since it started at the re-gear, that sounds to me like the culprit. I know, it's your boss...
OP
I'm also going to check run out on the rear axles. Should be able to pull the wheels and set the gauge up on the rotor hat and check for a bent axle shaft. I'll do the front too. I doubt it's that though. If none of this nets any positive results, then it's off to a shop cause I'm spent.
:monoloco:
:monoloco:
Don't always think you can eliminate the front axle by simply disconnecting the front driveshaft. If either of the front u-joints or axle shafts inside the front axle are shot, bent, or worn out, they still spin and can cause cyclic vibrations at speed.
I'm pretty sure I buggered up the RH u-joint when I installed it. Prob dropped a needle bearing. Gonna tackle it this weekend and post the results. Been chasing that vibration for months!
I'm pretty sure I buggered up the RH u-joint when I installed it. Prob dropped a needle bearing. Gonna tackle it this weekend and post the results. Been chasing that vibration for months!
OP
While I can't be totally sure about the front axle being a possible culprit, I replaced both axle u-joints about 6 months prior to the re gear when I installed a big brake kit up front. I also had a local offroad shop Check the front diff after I re-geared(the right side axle seal was leaking a bit, so they changed the seals). And, I also had the shop replace the front diff yoke with a HD Spicer u bolt style yoke just to rule out a warped yoke. Appreciate the input though, cause I'm sure I'm missing something here.
OP
Today's shenanigans took me to my shop at work to check run out, torque yoke nuts, install the front drive shaft, remove rear drive shaft and such.
First up, I removed the wheels, set up the run out gauge, zipped some lug nuts on the rotors and measured at the rotor hat. All four had minimal run out. Moving on, I installed the front drive shaft and removed the rear. Checked torque on rear diff yoke, good. Check output yoke on TC, umm, hmmm, loose. Could it be!? Crossed fingers. So, I tightened the yoke nut to 150 ft. lbs. Keeping with my original plan, I took the POS for a spin in front wheel drive so I could feel any difference. Sure enough, virtually no vibes to 68 mph with front drive shaft only. I was still hopeful that the loose rear TC yoke was the culprit, so I put it back on the lift to install the rear drive shaft and head home.
End result, no change. Vibes are no worse, no better. Now that I'm thinking about it, I suspect that the TC rear yoke was loose as a direct result of the constant vibes. Can't know for sure, but at least I found it and corrected the looseness.
So, to sum up, I've checked virtually everything in the drive train that rotates, adjusted pinion angles 9 ways to Sunday, checked control arm bolts, ball joints, unit bearings, replaced rear track bar, trany mount, been thru 2 front drive shafts, and 2 rear drive shafts, overhauled the transfer case and installed SYE. Evil monkey points the finger to the internals of the rear diff cause I don't know what else it could be.
First up, I removed the wheels, set up the run out gauge, zipped some lug nuts on the rotors and measured at the rotor hat. All four had minimal run out. Moving on, I installed the front drive shaft and removed the rear. Checked torque on rear diff yoke, good. Check output yoke on TC, umm, hmmm, loose. Could it be!? Crossed fingers. So, I tightened the yoke nut to 150 ft. lbs. Keeping with my original plan, I took the POS for a spin in front wheel drive so I could feel any difference. Sure enough, virtually no vibes to 68 mph with front drive shaft only. I was still hopeful that the loose rear TC yoke was the culprit, so I put it back on the lift to install the rear drive shaft and head home.
End result, no change. Vibes are no worse, no better. Now that I'm thinking about it, I suspect that the TC rear yoke was loose as a direct result of the constant vibes. Can't know for sure, but at least I found it and corrected the looseness.
So, to sum up, I've checked virtually everything in the drive train that rotates, adjusted pinion angles 9 ways to Sunday, checked control arm bolts, ball joints, unit bearings, replaced rear track bar, trany mount, been thru 2 front drive shafts, and 2 rear drive shafts, overhauled the transfer case and installed SYE. Evil monkey points the finger to the internals of the rear diff cause I don't know what else it could be.
IME, we never had an issue with vibs generated from a rear end that wasn't in bad shape, eg, blown pinion bearings causing the pinion gear to become loose. But that you would have found by now. If a gear set is set up significantly out of spec, you'd hear gear whine mostly under acceleration and/or steady driving. If you want, grab some gear marking compound, pull the cover, grease up 8-10 ring gear teeth, spin the wheels, take some pics, and post them up.
OP
I'll do that next. When I was talking to James Adams about the drive shaft conundrum, He mentioned he's seen Advanced Adapters output shaft bent right out of the box. If that were the case with me, you'd think I would have found that when I measured run out on the output yoke. Other option, maybe a bent/warped pinion shaft? Again, should have been discovered when I measured run out. And since I measured run out on all 4 wheels yesterday, think I can rule out a bent axle. I've got over 15K miles on these new gears, so if something were off in the rear diff, it should have launched by now me thinks. The fact that the TC output yoke was loose also concerns me. Jeep has been vibing for over a year and a half now, so concerned the vibes had loosened it. All the other yokes are torqued to spec.
Linderballs
Member
Curious to see what the fix for this is. Got mine regeared from 3.73 to 4.56 and above 65 vibes start. I was expecting it a little bit but am curious if it is normal like I thought because the driveshaft is spinning so much faster, or if it should be silky smooth regardless? Good luck Bob!