Hey guys, hope I'm posting this in the right spot. Just put in a 4.5” rough country x series lift in my 1990 xj. Everything feels pretty solid other than a sound I’m hearing now. Best way I can describe it is like a zip line or when you get a beer can stuck in your bicycle tire lol. It’s either coming from my front drivers side or from below me as i do feel very slight vibe under my pedals (may have always been there and im just over analyzing) . My first guess is gonna be that its driveline noise, I haven’t done a sye yet but plan to. Brake lines aren’t rubbing tires, everything has been tightened to spec. The sound only happens when i start getting to 30-40 km/h and changes in volume with my speed. Haven’t heard it in reverse, probably because im not going 40 in reverse lol. Got my brother to stand outside as I did a pass and apparently its almost un noticeable from outside. Its not super loud inside but definitely noticeable. Gonna assume everyone is gonna say do a sye, but figured maybe someone has heard this and they know it’s something else. Plan to do a sye in the future anyways, just wanted to save some cash for now if possible. Thanks guys

 

Do you have SYE?

 

Did you put the transfer case drop kit in temporarily ?? Sye or that supplied drop kit is needed...And the drop kit doesn't guarantee you won't get the vibes like you have... The drop kit is more or less a band-aid , the SYE is the way to go..
And now is when you'll find out the condition of your driveshaft joints...

 

I'm assuming that you have a jack, so pick up the rear axle and set it securely on some jack stands. Now carefully drive the rear wheels until you hear the noise, then poke your listeners and lookers around until you find it. If it's not making the noise with only the rear up in the air, it's safe to assume it's probably the front axle.

 

Thanks for the responses, i do have the t case drop in. We did a bunch of troubleshooting and think we found the issue. Must have been just bad timing, we decided to check everything over, all fluids on everything and found that my front diff was empty. We topped it up, but it still makes that sound so in guessing i whatever driving i did with it being empty hooped it. We tried jacking up the rear like mentioned and we didn’t hear it…just heard my rear brake being out of adjustment and my park brake stuck lol. Always something with an xj. Who knows maybe the sound is from front ds, but strongly assuming its diff howl. Gonna keep trying all my cheap options before I rip the diff apart, so definitely still open to thoughts of what it could be.

 

Forgot to add, we also realized that it stops the sound almost completely when i put it in 4 high

 

If
then "ripping apart" the differential IS the "cheap option".

That said, how did you determine the diff was empty? Did you pull the cover or just top it off?

Frankly I doubt it was "empty" because there would be screeching noise within a few miles.

So if you haven't done so pull the cover and look for debris. I'd pull the driveshaft to fully inspect the universals and to try to figure out if the pinion bearings are worn (you really need to pull the carrier but maybe you can jiggle it enough to see if bearings are loose or preload is gone). Check ring backlash.

 

Cause I'm thinking adding preload means it's a pinion something.

 

And even if it's just low you need to figure out why that happened. If not the cover or pinion seal then you have to look at the axle seals.