Rear drop...longer shackle?

'63 GMC, half ton, leaf springs, I would like to drop the rear a couple inches. Would using a longer rear shackle be 'wrong'? Seems like that would be easiest... what am I missing, besides a clue?

Below are a couple of images... the red item is the shackle in question... looks like I'd need a shackle twice as long as the desired drop... can these be bought?

Thanks

 

The longer shackle Would work but the rearend would have to be rotated to adjust pinion angle.You could monoleaf it or make a flip kit to put rear on top of springs then use blocks in the conventional way but I would be worried about longer shackles hitting the bed floor

 

Would it be possible to keep the shackles the same length, but move the front and rear attachment points to the frame both vertically 2" on the side of the frame---that won't mess with the pinion angle.

 

Yes it is possible, but you actually need to change the pinion angle slightly when raising or lowering a vehicle to keep the u-joint in line. If you look at any raising or lowering blocks you will notice they are tapered.

Look at doing a spring under axle swap, you should get almost 4" of drop.

 

Thanks for the info and suggestions, seemed a little too obvious oned I'd modeled it. I never knew lowering blocks were tapered... makes sense.

I think I read here about someone 'flipping' the rear axle, when would that be done?

Thanks

 

If you flip the rear axle, you will have 1 speed foreward and 3 in reverse. (but your truck will definately set lower).

 

On a car with 100" wheelbase, if you raise or lower the axle by 2", the angle of the pinion will change by about 1.1 degrees. I don't think that would make a damn bit of difference to the u-joints. And the greater the wheelbase, the less the angle will be.

 

flipping the axle moves it to the top of the spring truck guys use it so they can run lowering blocks to get a bigger drop and flipping in itself gives a 2-3"drop.You would have to fab up a collar to create a leafspring pad on the bottom of the rear instead of on top like the illustrations show but can be done relatively simple and cheap just make sure you weld it nicely as you don't want the rear twisting on you as you go down the road.

 

www.sporttruckdirect.com

 

I have to disagree with you here. Wheel base has nothing to do with determining the change in pinion angle, unless your driveshaft is connected between your front and rear axles. Since it's not, assuming a drive shaft length of say 55 to 60 inches, the change in angle is about 2 degrees, which still may not seem like much but the people who make the lowering blocks put the correction into their product, it must be there for a reason.