Help with vibration/noise.

This has me stumped..I'm not one for starting threads related to problems cause I can usually track down answers myself.

Anyway.. This weekend I installed my 3 link and new lift.
I went from 3 inch coil spacers, 3 inch blocks, and a t case drop to 4.5 re coils, custom 3 link and 3.5 re coils. No tc drop..have a hack n tap but haven't put it on yet. During the lift when accessing the upper shock bolt I broke the ccv hose..taped it up.

Soon as the lift and link setup was done I fired it up..immediately the vibration was noticeable even in park. The vibration will usually increase with revs. However once up to speed and say 2k rpms the vibe is gone. Under the hood you cannot detect the vib, only in the cab.
I've checked my clearance between the exhaust and floor and it seems like there is enough room..no codes on the engine. Obviously isn't u joints since its happening in park. Before the lift I had a vibration under heavy acceleration but not at idle or any other time..just when I got on the gas hard.

My tranny mount wasn't in the best of shape..but it wasn't bad either.

Ideas please!

motor mounts are shot from the tcase drop?

Would removing the drop make the worn motor mounts vibe more?

I know my tranny mount was in questionable shape..still all in one piece but it was easily moveable on the mount.

tcase drop will tear up tranny and motor mounts. thoroughly inspect them, usually you can just see the motor mounts in pieces. tranny mount I would definetly consider replacing it if you havent already . also, is your exhaust loose ? now that you shoved the crossmember back up, if the exhaust is pushed up against the floor and missing a mount or two it will do that. it did it to me when i got rid of the drop. and I had a bad tranny mount.

ditto what "blondejoncherokee" said. When I got rid of my TC lowering kit and installed the SYE, vibrations came out of nowwhere! After a very frustrating series of investigations...changed both engine and transmission mounts and vibration gone! Seems the TC lowering kit had "stretched" the mounts, or loosened them...and when TC lowering kit removed the mounts no longer held things tightly!

Was it a pretty noticeable vibe?
This thing used to be quiet as heck and butter smooth. Now when your in the cab it vibrates the dash like hell

If you can swing it, the brown dog motor mounts with the rubber inserts are awesome

Local dude is selling poly day star motor and tranny mounts for 100..

Reason I chased the vibe forever was that I did new 8.8 rear end, SYE, and new 4:56 gears front and rear (with e-lockers) all at once. I initially suspected something with the SYE...then something with the gears. Finally dawned on me that removing the TC lowering kit may have an effect. Since my motor mounts were original (280,000 miles), and the transmission mount had several years on it plus the stress of the lowering kit, I decided to replace both. Cured the vibes!

The vibes were more high frequency...almost a humming....would resonate at speed, but would not be noticible until 50 mph or so.

If you are NVH sensitve, the rubber might be worth the extra $5

My jeep only has 90k. The tc drop was only on it for a year maybe...could it have really wrecked that much shit?

It has to be something related to what changed when I put my 3 link on.
My buddy suggested maybe its just the more solid xmember...but damn that much vibration just from a new cross mber? The tranny mount wasn't in pieces but you could push it back and forth a bit.

IDK if this helps or not but if I leave it in drive, stay on the brake while pressing the gas the vibes are almost obsolete.

When removing a t-case drop, the angle at the engine end of the driveline changes.

Your transmission mount definitely needs changed. IMO a t-mount is either in good shape or it needs changed (we do not sell these). You should not be able to push it back and forth at all. Your original t-mount was significantly harder (durometer) than the original motor mounts. T-mounts usually split longways (like a sandwich) which often cannot be seen.

When checking your motor mounts, look at driver side first as it normally shows wear first.

Anytime vibration has been narrowed down to the driveline and felt in the cab, there are only three places that can transfer vibration from the driveline to the cab: transmission mount, driver side motor mount, passenger side motor mount.

If there's excess vibration after changing mounts, the source of the vibration also needs to be addressed, thus there may still a need to go through your driveline check list. I'd start with the u-joints in front.

Another thought, it's very easy to put a cross member on the wrong direction (The original can be bolted on in either direction. The driveline in an XJ is not centered. It was slightly right (passengers side) of center when it came out of the factory. Installing this backwards will cause the transmission mount and driveline angle to move slightly left of center.

Note: we've noticed some of the aftermarket cross member/skid designs move the t-mount the the center. One even moves it to the left of center. I wouldn't know about the one you've installed.