Just installed a mild lift (2.5") Now I feel a slight front end vibration.

an alignment might help... did you just get new tires as well? Might not have been balanced properly. A lift(that small) usually doesnt cause vibrations unless its stressed and weakend something else like balljoints or bushings. But I'd check the tires.

Did you relocate the trac bar up front?

Are you feeling driveline vibes or vibes thru the steering wheel?

You may need 2.5* shims in the rear if it's a YJ to help correct the angle for your drive shaft. Some folks also raise the motor mounts or drop the transfer case an inch to calm some of the vibes.

Check your tires first like AzTJ said... that's the easiest and cheapest and then go from there!

You DEFINITELY need to do an alignment after a lift. Heck, I would have them do both front and back just to be safe.

Thanks guys. As a matter of fact I did get some new tires a couple of months ago as well. I'll check balance and alignment...

It could be a drive line vibration also. If the drive shaft u-joints have been on there for a while they tend to wear into the angle they are used to. Something as simple as replacing the u-joints could solve it. I know that is what worked for me many years ago on my first 2" lift. HTH