gvns8

Here is the short version of my story. I want to get rid of all the drive line vibration on my xj... I have a SYE, the rear vibrates very mildly from 70-75mph. Then at 75mph and faster the rear hums very loudly and increases with speed. The front does not vibrate at all anymore.

-I went to a driveline shop and they checked both of my drive shafts on the balancing machine and said they are in perfect condition.
-I just put in the correct shims to point the rear pinion angle 1 degree lower than the driveshaft does. (was previously at 1 degree higher and had the same symptoms)
-I just rebalanced my tires which helped make it ride smoother, but humming continues from the rear driveline
-I checked the yokes on the t/c and pinion and they do not have any noticeable play when I moved them side to side by hand

Could it possibly be due to a bad tranny mount? I noticed that I can move the whole transfer case up and down slightly by hand to where it seems like it may be causing the shaft to vibrate

Thanks for any help- I would really like to get this problem completely fixed.

freegdr

jack the rear up sit axle on jack stand put in drive see whats happeng, at tires will hum

SeriousOffroad

Gavin
How much is "slightly"?

Have you checked for a bent axle shaft?

kenjen11

It might be tranny or motor mounts, I don't think it is the drive shaft if they were balanced a second time, but that depends on how good that shop is. I had to get my driveshaft rebalanced two times because it wasn't done right the first time.

ericfx1984

I would highly recommend using "Vibe Be Gone 2000 AND 1"

just kidding but you need to check everything... there are SEVERAL reasons that your Jeep could be vibing... even tires...

gvns8

Not sure if I feel comfortable doing that with the basic jack stands I have, due to the fact I would have to reach 75mph to hear the vibes probably. Maybe in a week or so when I have access to a shop I will put it on the lift and take a look.

I just measured the movement between the tc and the crossmemberand it is about 1/8" -so a little bit more than that I would guess at the t/c yoke.

As far as the axle shafts, I have not checked those, they are alloy, but yea maybe I will check those out. I noticed I can pull my axle shafts in and out of the housing by about 1/8" on either side is that normal?

I have tried using three different driveshafts in the rear (none of which vibrate when put in the front and it has the same symptoms at the same speed, so that shouldn't be it.

Anything else I could possibly check out? The rear differential was recently rebuilt with new gears and diff bearings. The only other things I could think of would be the axle bearings, pinion bearings, of possibly a malfunction with the locker I have back there (powertrax no slip)...but rather than just throwing more money at it I would like to isolate the problem. Thank you all for your help.

freegdr

putting the xj on a lift will not imitate the driving stance the suspension will be un sprung i never said do 75 mph just let some one get in and run it and watch see what if any things wiggling

freegdr

did the vibe start after the rear axle work if so theres where the issdue lies

gvns8

Yea I thew it on jack stands and didn't go too fast, and the two issues I noticed were that the transfercase was chattering a lot. The rear driverside drum brake was also slightly rubbing on and off, and that tire seems not as perfectly balanced as the passenger side tire. The differential was completely quiet and the diiff angle to the driveshaft looked perfect. I also checked the t/c fluid and it's full.

Also the vibes have always been there since I bought it- so yea before the diff work, but they have been way worse. It has been a combination of problems, but I have gotton rid of nearly all the vibes accept the growling/humming at over 70mph now.

gvns8

So here is what I am going to do:

1. rotate the front tires to the rear-maybe one of the tires are bad.
2. Just remembered my front unit bearings are not too great so I think I will replace those since those are tied to the t/c
3. I'll just replace my trans. crossmember with one from a manual xj since I want the extra inch of clearance and I'll grab that tranny mount also if it looks good to replace mine.
4. adjust the rear drum brakes... I also plan to do the zj disc conversion soon anyways so that will fix that minor rubbing.
5. pull the shafts and make sure they aren't bent and inspect the wheel bearings (bearings should be fine since if they were bad I would probably notice it at lower speeds also)
6. If none of that works, I will rebuild my T/C with new bearings or figure out what is causing the chattering and fix it.

Anythings else I am missing?? I will report back as I try each of these things. I really hope I can fix the problem without having to go through that whole list though....

freegdr

maybe its been the tire issue you see

gvns8

Well here is the update:

I took off the rear wheels, and felt more comfortable getting it up to a higher speed on the jack stands. The vibes/humming was bad without the tires so those are not the main issue, but I rotated them anyways.

I decided to remove the shaft and check out the yoke on the axle and it was full of dirt keeping the U-joint from settling fully in the yoke, so I cleaned all that dirt out. I got the shaft back on and got it up to speed while on the stands and it vibrated much less after that even around 70 or so.

I haven't driven it on the freeway yet to see if the humming is completely gone, but now I realize I probably have a new problem that I should address which may or may not be contributing the vibrations. The dang transfer case sounds horrible. There is a loud clicking/chattering noise coming from inside the case, so I guess the bearings must be bad in the case. I thought that chattering noise was coming from my brakes or something previously, but I guess the transfer case is to blame.