Hello,
I am a little in the dark on Axle Shims hope you guy’s can help.

I have installed the Trail Tough Y.J. lift on my Sammy, the alignment shop said my Caster and Camber was not within spec but adjust the steering gear box and it drives nice and straight.

Also the drive line vibrates when I engage the Transfer case and drive at any kind speed at  all, going real slow it’s good.

Brent at T.T. say’s this is all normal stuff, and did not bring up Axle Shims to me at all.

Will Axle Shims help me ? 
How do they work ?
Where do they go ?

Thanks in advance