So I just got done with my 3 inch aal lift and I'm pretty happy with it. Since lifting, I have noticed that some of the noises from my rear that I used to ignore have gotten more pronounced. Specifically a grinding or scraping sound especially when I let off the gas. It sounds like brakes stuck, but it doesn't stop when I hit the brakes... I'm kinda worried, maybe a u joint? Or a bad wheel bearing? Any ideas?

 

Your u joints are working at an angle they aren't used to and may need changed. I'd check there first.

 

Here's a pic of my driveline angle. I will get to the u joints next week.

 

A cv style drive shaft will help too i put one in my xj and in my tj exp if you plan on flexing alot or going any taller i went with tom woods shaft but thats my preference there are also diy junkyard shafts you can mod to fit but would start with good u joints and pull your diff cover and check for shavings and change the fluids can't tell by the pic cause I'm on my phone but if you have drum breaks worn springs can make the breaks drag alil also have fun with the new lift and be carefull it gets pretty addictive once the mods start

 

you need to change both ujoints and grease the splines under the boot at the tcase. if they dont stop after that, you need a tcase drop at the minimum, but should think about a SYE

 

I have the exact same problem as you,i fitted a full heavy duty 5 leaf spring so mine sits a little higher to the rear than the front,but it makes way more noise than when she was stock.The driveshaft appears to have pulled out quite away from the TC and the angle of the drive shaft looks to extreme.I had a driveshaft guy check the UJs and he said they were fine,but as said above they are working at a different angle.I have a TC drop kit which he thinks will cure it because it will put the shaft back at a more stock angle.Although my RC lift is 3" i think its higher,so fingers crossed we both solve this problem...

 

Ok, so I replaced my rear u joint, the one that meets the pinion yoke. Noise is still there, although it m didn't start till I made a hard left to turn around. That makes me worry about it being the diff, but it just doesn't sound like a diff sound... Next I'm gonna replace my brake springs, but I'm pretty scared..,

 

Is there any play when you wiggle the drive shaft?
If you're worried about the rear, take the cover off and inspect but I'd say a tcase drop would fix it. Sye is the way to go if you want to do it right though

 

No play and wiggle whatsoever when its in park, when in neutral I have a couple centimeters in each direction, but I felt that was normal...

 

Pinion angle looks to be incorrect. The pinion should be parallel with the transfer case output shaft. With a SYE/double cardan shaft (which you don't have), you'd be about perfect. But with the stock shaft, you're pulling on the splines with each rotation. That can cause a nasty vibration which may lead to seals leaking/premature bearing and u-joint failure.

 

What about a t case drop?

 

The t-case drop would make it worse (pinion would be even higher). You're probably going to have to use an angle finder on the driveshaft (where it lines up with the t-case output shaft/slip joint) and the pinion to determine which shims to use to rotate the pinion down so it's parallel with the t-case output shaft OR if you want to spend more money, get an SYE and double cardan shaft and possibly some shims. Depends on the measurements your angle finder reveals.

With the stock 2 joint shaft, your pinion and t-case output should be parallel like this: http://www.4xshaft.com/images/2joint_angle.gif

With an SYE and double cardan/cv shaft it should look like this:
http://www.4xshaft.com/images/cv_angle.gif

 

How would the pinion be higher if I dropped the t case? And how do shims work?

 

Ill tell you this, I had similar problems. I originally installed a budget lift of 2" then wanted to go higher. I then put on a Rough Country 3" lift and then a complete 4.5" and now sporting a 6.5" lift with spacer on front to level out. My driveline was stock until several months ago when I put on a Tom Woods driveshaft. When you change the lift, the drive angle changes also. The pinion bearing will make noise when you let off gas while driving and its like a humming noise. The bearing is going bad and I would recommend changing the driveshaft because its a slip and will continue to slide in and out when flexing. I have a 231 Tcase so I also put on a SYE kit. And if you ever decide to go up to 33" tires think about getting it regeared to higher than stock. It will all make a huge difference.

 

The transfer case drop is a band-aid for people whose pinion is too low and output shaft is too high. From the picture you posted, you don't have that problem.

Your pinion is too high with regards to the transfer case output shaft. So dropping the transfer case will put the transfer case lower and the pinion higher.

The easiest way to fix the problem is with some steel axle degree shims (do not use aluminum, they are known to crack). You'll need to put them in with the "big end" of the shims facing toward the front of the vehicle. This will lower the axle pinion and correct the binding of the u-joints during rotation of the driveshaft.

The goal with shims is usually to point the pinion up toward the output shaft for use with a slip yoke eliminator and double cardan/cv style driveshaft (that has the slip at the axle end of the driveshaft and an extra u-joint at the output shaft).

In your case, you have a pinion that is already pointing toward the output shaft and with a 2 joint driveshaft (that has the slip at the transfer case end of the driveshaft) this is not optimal and will cause binding. This is the opposite of what you need. Your pinion angle and the transfer case output shaft should be parallel. So you'll have to install shims backwards to get a negative degree shim.

But before you can get these angles lined up properly, you'll need to measure the pinion angle to see how many negative degrees the purchased shims must provide so that the pinion and output shaft will be parallel. You can purchase shims in various degree options.

Any DIY home improvement store should have a mechanical angle finder you can use to make these measurements. Then you can buy a pair of degree shims and install them between the leaf springs and the axle tube perches. Make sure you get new steel shims, new longer u-bolts and longer centering pins.

If you can't do this yourself, you can always go to a driveline shop and have them measure and install shims to correct the problem. They can also rebalance your driveshaft to further reduce vibrations. Other variables they can look at are shackle length and angle.

Hopefully, this helps you get your XJ back on the road and vibration free.