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Help me fix my 60-70mph rumble/vibration!

F

Fred85

NAXJA Forum User
Location
Orange, VA
2001 xj 101k 4.0

As far as mods, right now i only have an AAL in the rear to "fix" the very badly sagged stock springs until the OME stuff goes on. I also have a hack-n-tap SYE with a front xj shaft, no shims (shouldn't need them yet right?)

I crawled around underneath yesterday to check shafts for play and everything is tight. I even took off the front shaft and drove around, but it didn't fix the rumble. My tires are pretty new and i'm fairly positive they are balanced (245/70/16).

Give me suggestions, if i didn't mention it then it is stock.....i'm seriously considering taking it to the dealer (which is obviously a last resort)
 
You need to check your angles,you may very well need to shim it!
 
Agreed, if you put the SYE in, the pinion angle should end up a degree or two below the driveshaft itself, not below the TC output shaft like with a standard rear driveshaft. You're going to need to shim it because of that.

Also, since you have an XJ made after 95 (96 and later MYs were afflicted) your TC output housing/slip yoke design is the "modern" one, you might need an SYE or a TC drop to kill vibes even with a stock suspension height, there was a TSB to address this (only applied to some XJs without UpCountry, applied to a lot more with UpCountry suspension package)
 
My stock 2000 sets up a small vibration/rumble when you get up to about 65. It's not real bad, and I kind of figured it was "normal". Does anyone else NOT have some of this vibration?
 
winterbeater said:
My stock 2000 sets up a small vibration/rumble when you get up to about 65. It's not real bad, and I kind of figured it was "normal". Does anyone else NOT have some of this vibration?
Click to expand...

My '96 has one from the front, I think the passenger side. I was going to rotate the tires and see if it goes away. It only does it from 55-65 mph. I have not been able to track it down. Its not DW, it feels more like the wheel is out of balance and wobbles. Maybe ball joints?
 
could be bearings. Does it get louder or quieter when you go around corners left/right?

I had absolutely no vibes under any amount of acceleration - until I lifted my 96. I get vibes from 5mph up now, though I can't hear them unless I really stomp on it now that I've got mud terrains on it... eventually when I'm working on something else I'll end up getting around to installing the hack-n-tap SYE I have sitting in the closet.
 
kastein said:
Agreed, if you put the SYE in, the pinion angle should end up a degree or two below the driveshaft itself, not below the TC output shaft like with a standard rear driveshaft. You're going to need to shim it because of that.

Also, since you have an XJ made after 95 (96 and later MYs were afflicted) your TC output housing/slip yoke design is the "modern" one, you might need an SYE or a TC drop to kill vibes even with a stock suspension height, there was a TSB to address this (only applied to some XJs without UpCountry, applied to a lot more with UpCountry suspension package)
Click to expand...


...what?
 
the noise is independent of everything else it seems, it is constant no matter if i am turning or going straight

how do you check the tranny mount? the rubber isnt cracked at all, but i can move the tcase a tiny bit if i push on it
 
mflueras: what should I explain better? acronyms, or did something else confuse you?

Fred - generally, a long prybar or piece of steel pipe works nicely. Pry around with it, just make sure you don't bash it into anything sensitive or pry hard on something bendable (sensors, linkages, pan, etc)
 
mflueras said:
...what?
Click to expand...

Read it again, all very true.

This sounds like the unfortunately normal late model rear driveline angle issues. If so, the noise/ vibration will change with pinion angle, done one of two ways: throttle or brake. As already explained, though, the pinion angle that works best with a two ujoint rear driveshaft will NOT work smoothly with a three ujoint shaft.

Transmission mount will have a little bit of give, it has to since it's rubber. They don't normally fail unless soaked in oil.

A big part of diagnosing problems like this is having the 'feel' to tell whether it's wheel/ tire or driveline vibration. Very different sensations and noise. Wheel/ tire (and wheel bearing) noise is low frequency while driveline vibrations are much higher frequency. Tire issues could be characterized as rapid thumping while driveline issues are more of a buzzing change in the cupholder type sensation.
 
The guy already has a SYE installed so this post doesn't make sense:

Also, since you have an XJ made after 95 (96 and later MYs were afflicted) your TC output housing/slip yoke design is the "modern" one, you might need an SYE or a TC drop to kill vibes even with a stock suspension height, there was a TSB to address this (only applied to some XJs without UpCountry, applied to a lot more with UpCountry suspension package)

Also, again because there is a SYE installed, it is not normal late model rear driveline issue.

Ther problem is the SYE is installed without shims. With the SYE the pinion has to point at the transfer case therefore shims are needed. Less of an angle correction at such low lift, but needed nonetheless. When stock the output shaft and pinion u joints need to be in phase to cancel eachother out. Vibrations result when they do not.
 
mflueras, that's two in a row. Read more slowly, it all makes sense. :)

dagr8tim, that goes back to what I was saying about telling the difference between wheel/ tire and driveline vibrations. They are two very different things, but easy to differentiate between once you know what you're looking for.
 
Call me a moron if you will, but I just don't get how a hack and tap SYE and late model drive train vibration relate? He doesn't have unsupported tailshaft, he hacked it!
 
I know! Quoting my own post here.. "the pinion angle that works best with a two ujoint rear driveshaft will NOT work smoothly with a three ujoint shaft."

He has an SYE and no shims.
 
And my point was that this was not "normal late model drive train vibration" which as you pointed out was caused by the unsupported shaft.

The original "what" was about the suggestion that he might need a SYE or Tcase drop after acknowledging the SYE in the previous paragraph.
 
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