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IRO SYE vibes!!!

I never said it was coming from the front I did say I felt a thumping under my feet which I found out to be the exhaust hitting the cross member and that has been fixed. I cannot stress enough that this has nothing to do with anything else and I know this because I drive it to work and it dove with the same vibes it always had and right after the install I had the same vibes plus more! It HAS to be something related
to the sye and new ds...stuff doesn't go bad in a matter of hours!
 
I looked at the pix...

Is that driveshaft fully compressed?

Add: I would have a bit less pinion angle to compensate for WOT acceleration.

What happens when you remove the rear driveshaft? Do the vibes continue (use 4WD to verify)?
What about if you remove the front DS?

Ron
 
Last edited:
xjcannon said:
Maybe you shouldn't be full throttle, in a lifted jeep, on the highway.:nono:
Click to expand...
Your post makes no sense.

Is the pinion supposed to be pointed at the output or parallel to the output when running an SYE? I can never remember. I ought to just take a look at mine and see how it's aimed. :D
 
First thing I would do is just pull the rear shaft and drive on the front alone.
You need to make sure where it is coming from. If it is from the rear, put your front shaft back there and see if it goes away. You will now have it narrowed down to either an issue with a single driveshaft or your angles are bad in the rear.
 
To try to eliminate your "IRO" driveline from being the problem. I would take The "IRO" off and drive in 4 high. This might tell you if the "IRO" needs some TLC if your Vibes go away.

Looks like I was a couple seconds slower than jonzer
 
Ok ok ok I get it everyone wants me to remove the rear ds and try to eliminate or narrow down the problem o being in just the rear and I totally respect your opinions and appreciate the help but that doesn't make any sense! What I keep saying is that it had vibes under accel 30-35 under a hard acceleration before I did the sye and now right after the sye the same day on my way home...it has the same vibes PLUS more at higher sppeds that are constant and not just when I'm under a hard acceleration that were not there before the sye. So, that being said, shouldn't that automatically eliminate the front shaft entirely since these new vibes plus appeared after I did the sye? Nothing was changed on the front and the way I keep thinking is, how could it be the front there's no way possible anything went wrong with the front from it sitting in the air at work while I did the sye. I think like some of you that it's either the angles which I will measure and post today, or something else! There's not logical way it can be related to anything other then the rear.
 
I know all the talk about the problem coming from the front possibly is sounding ridiculous, but if you removed the T-case drop when you did the HnT, something did in fact change in relation to the front end. Technically the DS angles on the front should be better now without the drop, but you never know. Just a thought after re-reading your original post.
 
keep0njeepin0n said:
Ok ok ok I get it everyone wants me to remove the rear ds and try to eliminate or narrow down the problem o being in just the rear and I totally respect your opinions and appreciate the help but that doesn't make any sense! What I keep saying is that it had vibes under accel 30-35 under a hard acceleration before I did the sye and now right after the sye the same day on my way home...it has the same vibes PLUS more at higher sppeds that are constant and not just when I'm under a hard acceleration that were not there before the sye. So, that being said, shouldn't that automatically eliminate the front shaft entirely since these new vibes plus appeared after I did the sye? Nothing was changed on the front and the way I keep thinking is, how could it be the front there's no way possible anything went wrong with the front from it sitting in the air at work while I did the sye. I think like some of you that it's either the angles which I will measure and post today, or something else! There's not logical way it can be related to anything other then the rear.
Click to expand...

how hard is it to remove the front shaft? 5-10 minutes, tops?

removing the transfercase drop changed all the angles, front and back.

sometimes ujoints will appear tight but will vib from running at new angles
 
It's not the fact that pulling the shaft is hard or takes too much time...it's the fact that I didn't understand why the front ds would be the problem but I never thought about the t-case drop being removed causing a problem in the front. I'll check that as well.
 
Ok so it looks as though I've found part if not all of my vibe problem...Rear DS angle is 12* and rear pinion angle is 12.5*.....now what's the easiest and quickest way to figure out what degree shims I currently have and which ones I need to replace them with???

I took a picture so when I get home I'll post it up!
 
no, the spring is on top of the axle... smaller shims would lower the pinion toward the ground. Fatter shims would raise it. (fat part of the shim goes on the gas tank side of the axle)
 
Ohhhhhhh I gotcha!!! I was thinking of a spring under setup! Well maybe I'll just remove them all together and see what that does...if they are 3* shims which I am guessing they are, will that put my pinion too low?? That would make it 9.5* pinion and 12* DS which puts the pinion 2.5* lower than the DS...thanks for your help so far guys.
 
FWIW. I just went through the same thing on my ZJ. New SYE and driveshaft with vibrations above 50 mph. I had the ds balanced 3 times at 2 different shops and each time they said it was ok. I finally figured it out and had one of them replace the slip spline and the tube. That cured 90% of the vibes. The dynamic balancers used now, don't spin the shaft fast enough for a slip spline flaw to show up like it will under load at high rpms. I have 488 gears, so the ds spins much faster than the balancers do. I have Clayton long arms and there is no axle wrap, so my pinion is equal to the ds angle.

I determined that the problem was in the rear ds by removing it and running on the front in 4wd. The vibes were gone then. You should do the same to confirm that the problem is or is not in the rear shaft.
 
Ok here are some pics of what my shims look like...they are installed with the fat side pointing to the rear (gas tank side)......should I remove them?


photo2-1.jpg



photo-1.jpg
 
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