Hi!
On a leaf suspension, one end of the leaf is attached to a frame anchor point on a pivot. The other end is attached to a shackle, and then in turn attached to the frame.
With Shackle lifts - a very moderate lift from stock will effect your lateral stability at highway speeds, and if you are towing something. You may want to offset this by leaving your rear track bar installed - although I don't know too many vehicles other then tow vehicles that leave this in place.
It will lift your vehicle half of whatever you pick which is oversized to the oridgonal. IE - if the oridgonal is 4", and you go 6", you get one inch of lift. Very minimal. Only a fool uses shackles as thier primary way of lifting a vehicle to make room for tires. And, if your springs are already weak, this won't help them.
Pro - more wheel travel - a lot more if you get one of those fancy twisting ones, or piviting types.
Pro - minor lift, usually to offset a vehicle addition. IE - to offset a winch, or welded spare tire holder, etc.
Pro - in the case of a YJ, can be used to protect the fuel tank, and exhaust pipe when used on the rear.
Con - oh sooo many.
Con - your lateral stability at highway speeds, ain't so good no more.
Con - your approach and departure angles will be effected (not certain how much on a Ford though)
Con - during high RTIs, your frame mounts may not be able to handle the leverage produced by oversized shackles. Mine are only 2" over, and I've broken BOTH sides within one year of installing them.
Con - No a very good idea on weak, or poorly sized springs - it "pulls" on them under heavy load.
Con - your axle will now be significately looser - less lateral stability. If you had problems with your tires rubbing up against the side of your wheel well, you will have a lot more now!
Con - on the front, your steering will be looser, unless you left in your track bar in.
Con - on the front, you may need to re-adjust your steering stops, as your tires are much more likely now to hit other components when under RTI or lateral load.
Con - it's a sure tell sign of a true idiot when you see a short wheelbase vehicle running 6" of lift with nothing but shackels because they were cheap. Want to save money, use your grinder on your sheet metal - and sometimes you just have to.
Con - I could go on... but my figures are getting tired... needless to say, do NOT go longer shackles, unless you have a dang good reason for it.
axle...
ps - As you can see, that's just with shackles... any lift, even a 1" one, can have problems... lots of them. Shackles are the cheapest - and the most costly.
Good luck!
