1ImperialSS

iTrader: (5)

in colby's pictures, after the drop the angle is more negative. which is not my case, ive looked at it and compared it to my dads. i think the problem with colby's picture is that in reality, (i think, my trucks not near me now) the drop shackle is placed in the rear mount of the leaf spring and pushing that down would turn the axle more upwards, making colbys picture ultimately backwards? i think im believing the stylin concepts article a the moment but and no unopen to other schools of thought

2004SSS

iTrader: (25)

what it does , is rotates the angle of the axle, the shimd help the axle turn a bit more down in this case so that it has the same angle as it would have when it was stock.

Coban

iTrader: (14)

Well if you raise the back of the leaves, the front will go down. The way I always saw it was that you needed to raise the front of the diff back up. In what way is colby's pic wrong.

1ImperialSS

iTrader: (5)

because the leveling kit contains longer shackles, which,if i remember right, are attached to the frame and push the backof the spring down which would turn the axle up. hold your right are out with your fingers pointed to the left, push your elbow down and if a tube was on your forearm it would be rotated upwards

Coban

iTrader: (14)

The back of spring is held higher with longer shackles. Yours is now closer to the bed with a longer shackle.

CHEVY6000VHO

iTrader: (2)

Shorter shackles raise the truck (places axle further down), and longer shackles lower the truck (places axle further up into the truck).
Colby's diagram is correct. Styling Concepts is correct also.
You just have to look at it harder and longer I guess.

Jim

Coban

iTrader: (14)

Bout time someone else chimed in on this.

Coban

iTrader: (14)

Here the way I see it. There are 2 situations.

1. Shackles and Hangers
Using Shackles and hangers means the the level of the axle in relation to the frame and drivetrain has changed. In this case, you need to angle the front of the differential down slightly. Since Chevy's have the leaf springs on the top, you need to install the Shim with the FAT SIDE FORWARD.

2. Shackles only
Using shackles only means that you change the level of the axle AND the Rotation of it. (Refer to Colby's diagrams on first page) The front of the differential is now pointing down, so you need to angle it back upward. You need to install the shims with the FAT SIDE BACK.

Does everyone agree with this? Of course, there are 2", 3", 4",.... drops so not everyone is gonna be the same. Some trucks dont ever need them, but its a good idea to keep in stock spec. Vibrations tell you something is f**ked up.

Let me know what ya'll think.

1ImperialSS

iTrader: (5)

ok so now im totally confused... ha ha so stylin concepts article was referring to people with shackles and hangers? i have ony the drop shackles but it appears the the angle of the axle is not as negative as it should be but im not sure what it should be 100% either.... im getting a vibration at 45mph. i have just shackles, belltech leveling kit like 80bucks. so i need fat side back? pretty much i figure im gona have to install them one way, drive it and see, and then if it still sucks then reverse it...dang this is a pain unless we get this figured out.

BigCountryx

iTrader: (3)

Here goes.... If the axle is rotated, but remained in the same position (height wise) what you guys are saying about the fat side forward would be true everytime, but you must take into consideration that the axle to tranny orientation is changing in this situation. That means there are multiple varriable now. In my case, with shackles only, my pinion angle was high, which is opposite of what most people would expect. Raising my carrier bearing assembly fixed my problem. Shims may have fixed it also, but it's not the route I chose.

Bottom line IMO is that forget all of the calculating about what it should do and just get you a cheapo angle finder from harbor freight and measure your angles. If you get your pinion angle 1-2 degrees below your output angle, be it by raising or lowering you carrier bearing, tailshaft of your tranny, or pinion angle, get those angles right, because that is the only thing that will rid you of vibrations.