hello I'm just looking for a better understanding. After lifting about 3.5 inches (OME cs0033rb and rustys upfront) I noticed some vibrations. I was honestly expecting them, so I installed a tc drop spacers and it helped a tiny bit but they're still pretty bad. Especially on the highway. Long story short I look at the drive shaft angle and was wondering if shimming the axle would help. I know sye are a definite but would that really change the angel as well? Any input would be appreciated thanks

 

There's lot of variables it could be, depending on where the vibrations are coming from. It's probably not from your rear driveshaft because the TC drop would have made a significant difference, although an SYE is definitely preferred. What type of lift was it (i.e. What was included in the lift?)? Did it come with replacement upper and lower control arms?

 

You should post the info on your jeep, its makes all the difference. You need a SYE and new CV DS and the rear pinion needs to be pointed directly at TC output -1 degree. TC drop is a waste of a band aid. Plus, your rear U joints are also mad at you for changing their angle and thats a good deal where you probably feeling it from

 

I hate mis-matched parts in a lift the coils/leafs should at least match same company in your case Rustys was a VG choice all of there leafs/coils made in NA where as the leafs you have were not, most likely China on the OEM so called ones. Are you sure of the lift height you have I'm guessing the Rustys coils are 3" and I have no idea what the exact lift those leafs give you, you have to measure. All lift kits are like a new stock setup and should ride about 1" higher in the rear. List all details of your lift that you installed for it.


With the drop kit check the motor/trans mounts for damage also. With a 3" lift your stock U/LCA's will be fine with the properly BS wheel for a larger tire if used. You do need an adj. track bar (DON'T re-drill and mount the stock one) just buy an adjustable one.


An SYE is the proper way to go on any lift but you can get by for a while with the drop, be advised it is very hard on both engine and trans mounts. I have an SYE and shims both installed in mine and others do use them also.

 

Sorry For the lack of info but it was a lift i pieced together. The rear included OME CS033RB springs on stock shackles and the front has rustys 3 inch coil springs with IRO trac bar and Rubicon Express Superflex LCAs. The angel at the pinion doesn't seem proper. I added a RE TC drop and it definitly helped with the vibrations but I'm still not happy. The rear does sit at a slight rake which i like to accomedate when its loaded, but i can measure for lift i just dont know exactly from what spots to measure? center of hub to fender? axle to body?

 

So I Went down to a drive line shop and they told me I needed to have my rear spring perches cut and welded with the axle rotated up to adjust for the change in drive shaft angle. They also mentioned there was no need for a double cardegan (cv) at the out put shaft. Lengthening my current drive shaft would be sufficient to adjust for my lift. I'm kind of lost now, I thought shimming the rear would adjust for the angle?

 

Here's my Drive shaft as it sits now, if it helps.

 

Hmmm, They must not know Jeeps very well..On my 2000 at 4.5" I had bad vibes, I was using my stock shaft and t-case drop at first, still had vibes. Went and got a SYE and a CV shaft, 4 degree shims. Now I have zero and I mean zero vibes.

If I was u I would get 3 or maybe even 4 degree shims, a SYE and CV shaft.

If they cut and move the perches so the angle of the axle has the shaft pointed to the t-case, that still wont work. Might make it worst, yes if you had a CV shaft and cut and rotated the axle that would work. but not for a stock shaft.

The stock shaft should look like this all the time cause of what kind of shaft it is. A 2 joint shaft




Here is how a proper CV shaft set up looks like, 3 joint shaft.

 

how exactly would i determine the degree of the shim needed? subtract the drive shaft angle by the pinion angle?
Also, per the first diagram, assuming the pinion angle is correct, would extending the drive shaft to the proper length eliminate the vibration? Im just trying to fully understand the best solution before i start throwing parts at it and thanks for the input

 

Here is some reading.

http://www.xjtalk.com/showthread.php?t=7354

 

Thanks! but back to my other question, would lengthening my drive shaft, assuming my angles are correct, eliminate my vibrations?

 

I have learned a bit about this...the hard way, thru trial and error. I initially did a 3" RC lift, now at about 4". Had driveline vibration. Chased my tail trying to eliminate it. Now I have it as good as I can get it...but still not to my satisfaction. Here is what I did:

Driveline was checked and found to be off-balance; cut, rewelded and balanced driveline.

Installed, removed and reinstalled 1" TC drop. This is not good as it deforms the rubber Eng/Trans mounts. I replaced those too.

Mucked about with 2* and 4* driveline shims, tipping the axle both directions...first to get the two shafts parallel (which didn't fix it). Present config is TC drop installed and 2* shim in front of the axle to point it up towards the tranny. This is the least vibration of anything I've done.

Bottom line is I should've listened to these guys and pony'd up for an SYE & driveshaft. Factory configuration with that big, long output shaft protruding from the TC unsupported by any bearings is...not good unless the driveshaft sits perfectly inline with the output shaft at normal ride height.

 

Yea i figured to have the drive line shop mess with it and the fact that i didnt feel comfortable with what they told me (not trying to say i know more)and after much reading last night, I just decided to go with a SYE and front drive shaft. Bc this xj is my dd and road trip machine id rather have everything done the right way. hopefully once installed my vibes are gone and i can drive happy again.

 

Excellent idea, if you do use a front DS for the rear do rebuild it before installing if its questionable at all.

 

X2 on SYE and CV DS. Its the bullet that all modified XJ's have to bite at some point. You could have it installed faster than it takes to read all the "SYE or Tcase drop?" pages..