Extended length shackles only raise the rear of the spring which changes the pinion angle of the differential-not a good thing.Because of the increased moment arm, the long shackle will cause some stability problems in a hard cornering situation.Longer shakles would not be my choice. RW

 

You are partly correct. Extended length "drop" shackles do raise the rear mounting point of the spring, which in turn lowers the rear end approximately 2". This will indeed give you some negative pinion angle (I think this is correct) which is not a bad thing. People have been installing "drop" shackles for years without any adverse problems. If this concerns you, 2 degree pinion shims can always be added to correct the pinion angle back to the stock parameters.

 

I agree with suds5.4. I think the degree angle with the shackle is one mod that has the least of worries. I've seen 18" lifts and bagged slammed out trucks that last 150K miles and still ticking away.
Plus, I would rather be added or removing components that can be put back (also for warranty reasons) than permanently altering the vehicle.
Just my opinion though.

 

I don't know if anyone has said this yet but www.truckaddons.com has lowering shackles, 2' by 5' lowering kit, other cool stuff for the 04' F-150.

 

Better prices can be had elsewhere.

 

Forget the shackles and just take the blocks out, you can shim the bolts or buy new shorter bolts. If you want to return to stock put the blocks back in. Its the best move I've made on the truck!! JT Ford

 

4X2 does not have blocks! RW

 

Why do they make it azz high to begin with? The one above that was lowered in the back looks a tad azz low. Just my opinion.