Your vibration/ noise will probably be back in a little while. When you dropped the T-case you changed the power train angle. This causes the motor and tranny mounts to use different parts of the rubber (maybe a not so warn out chunk). That would make the noise go away but only temporarily.

 

i think mine does same thing. does it do it while just sitting there in drive? it might be ur transfer case. try puting ur truck in nuetral and idling there

 

My 87 jeep cherokee starting making a noise when I drive now. I noticed it happens when I hit a bump and apply the gas petal. It sounds like its under my feet but then sometimes hear it towards the rear. What could be the problem. If I let the gas pedal off and push down the noise is there anymore. Whats the deal anyone help me out.

 

I have a constant grinding noise in the rear when under power which quiets some when I let off the gas. I'm hoping it's the rear driveshaft u-joints and not a bearing somewhere. But the drive shaft has no play when i move it around with my hand so i don't know.

 

I recently had a new transmission put in my 2000, along with a new transmission mount, it got rid of most of the noise, until i put my front driveshaft in. So I think the two main sources of the noise would be the transmission mount, and replacing the ujoints on the front driveshaft would solve the rest.

 

 

Openin' this ***** again. @Jake149 what did it end up being (if you can even remember back 8 years)? My situation seems to be the same or similar to yours. The noise occurs on acceleration from a dead stop, not at idle, mostly while I am turning although as of late it happens sometimes when going straight. After a few seconds of acceleration, the noise goes away. It sounds like it is coming from the front and you can feel the vibration on both passenger and driver side when it happens. I removed the front driveshaft but that has not made a difference. Some facts:
- In the past 2 to 3 years all the U-joints in my front axles and front driveshaft have been replaced. As well as my wheel hubs.
- Both engine and transmission mounts were replaced in the past year.
- have checked the rear driveshaft multiple times never finding any play
I'm gonna take a thorough look through tomorrow even checking the steering pump pulley and flywheel bolts as recommended. It is a sound that is rotating so I believe it's most likely a part that spins (Elementary my dear, Watson!). Just wanted to see if anyone had some new revelations about this.

Thanks in advance!

 

Figured it out, and it was so ridiculous thought I'd share:
Checked all the aforementioned areas. When I started him up that morning I had a crazy noise which I thought pointed directly to the flywheel bolts, those were fine and the noise turned out to be my distributor. Found that my rear driveshaft u-joints were just beginning to get a little loose. Figured that's probably it.
As I was getting out from under the Jeep, I was doing a final scan of the underside. I noticed a few nicks on my exhaust pipe. Turns out the yoke on my front differential was hitting the exhaust pipe while turning. About $10 in exhaust hangers fixed it up.
Just wanted to post this as an example of how simple yet random some issues can be. Take your time and look carefully.

 

So I had the same exact issue. I drove my 99 Xj from El Paso to Seattle with no major issues ( had to do an AC delete near moab due to the AC seizing) other than that it was driving, shifting fine with no problems at 70+ on the highway. A week after I got here, all of a sudden had trouble starting, but nothing major, just took a few tries. Then all of a sudden that grinding noise. Sounded like a fan hitting something metal. I initially thought it was my fan hitting the hood release wire but I zip tied everything down and still no resolve. I started noticing it was always in 1st gear when I accelerated from a dead stop, but if I grandma drove it slow it would not make the sound. Once I hit 2nd gear there was no noise. I could drive it on the highway 70+ and no noise. the noise sounded like grinding gears in my transmission while accelerating in 1st gear, worse when at a dead stop up hill. If I let of the gas it would stop. No noise revving at idle. When I'd hold the brake down and press the gas in 1st it would grind. Well a few days later it barely started, so I drove straight to mechanics said it was the starter and wanted $480 to replace and told me the grinding noise was the rear Diff and wantedn $2,800 to rebuild. So I'd did what any XJ owner and good American is used to and told them to **** off. Put in a starter myself but still no start even thoethe starter housing was kinda ground up. After going down the XJ form rabbit hole I figures CPS sensor. New CPS and it started right up, however the grinding was still there. Started with new fan clutch, still grinding. New tyranny mount( checked fly wheel bolts and they were fine), grinding worse, especially when turning. Thought maybe therebm was too play and causing my azzy transfer linkage to shift. As i was putting in new motor mounts I double checked the flex plate and it was the God damn dust cover ....I'm sure the motor mounts helped cause the old one were proper ****ed but somehow my flexplate bolts were hitting the inspection cover. Took it off and no noise and peace of mind.