Sorry if this sounds redundant guys, but can someone tell me why I now have a vibration at 40mph after I lifted my Jeep 3"?

 

Oh yes, it's redundant. A simple google search would have yielded you answers faster than waiting for somebody to tell you.

One possibility is that your transfer case and rear axle are too far apart because you lifted it. A common band-aid is to buy 1" t-case drop blocks.

 

The right way to fix it is a sye.

 

I thought 3" was generally considered a small enough lift to not have to worry about sye/tcase drops? Or is does it vary between trims/years?

 

Some people have vibes and some dont.

I have installed several sye's and I personally would not run one, nor a transfer case drop.

I would rather run degree shims under the leafs. Works well, cheap, and no adverse effects.

 

It can vary jeep to jeep and lift brands.

 

I run an SYE and degree shims both now at 4 1/2" but at 3" only had a TC drop kit didn't know any better and was on there when I bought it.

 

So are you saying a 1" transfer drop is bad all around?

 

T case drop is a waste. Lift you jeep 3 inches to only loose an inch of clearance with t case drop. Also puts your clutch fan closer to radiator. Degree shims re way to go.

 

I would only run a t case drop if the jeep is my only way to work,And it would be just long enough to get a sye kit installed on the jeep.

 

Shims are much better idea and you lose nothing.

 

Do you guys know the rule of thumb as far as what size shim I need for a 3" lift? The vibration is literally minimal at 40 mph but then goes away once past 45mph.

 

You might do a bit of inspection on the front steering tie-rod ends, and especially the track bar. That vibration you feel may not be related to the transfer case as the others here are suggesting. It might be, but it might not be. Check the other possibilities...

 

I just recently lifted mine with the RC 4.5" X-series lift and installed the TC drop last night, hoping it would reduce the vibes until I order the SYE kit. All driveline vibes are gone. I still plan to do the SYE but it will be in the spring.

That being said, I still have a vibe in the 50-60 mph range but I can feel it in the steering wheel. Everything in my steering and suspension is brand new except for ball joints and the steering box. I'm taking it back to the tire shop on Wednesday because I'm thinking the tires need rebalanced.