1 more shackle install question

[red86chevy]

Does any one think that When I install my lowering shackles (2") that I will need to correct my pinion angle with wedge shims? I am only lowering the rear 2". The front is going to stay at factory height, so the truck will be sitting level. Or will it not be enough to hurt anything?

Thank you

Jeremy

[86 GMG]

i would like to know also i am doing the same thing

[red86chevy]

also I noticed in summitt that the shackles PN sum-g904000 say they are for 1988-2000 models. Will these work on an '86?

Jeremy

OOPS never mind just noticed the sum-g756 which is for my application.
SORRY.

[bigblock73]

your pinion angle will be just fine.

[red86chevy]

Thank you.

[piecesparts]

I have lowered more than one truck, the amount that you are going is not going to be an issue. You can even put the front hangers on for the full four inch drop and it will be just fine. The major companies that sell these items have worked out all of the particulars and if it needed pinion work then they would offer that info when you purchased the kit. Belltech, DJM, and others are silent in thie area for what you want to do.

[bigarmzz]

mines lowered total of 7" in rear...no shims...pinions fine

imo, the "higher quality" lowering components have this worked out in there stuff, so shims arent necessary....imo

[1FaastC10]

Originally Posted by bigarmzz

imo, the "higher quality" lowering components have this worked out in there stuff, so shims arent necessary....imo

you cant really mess with the design of a shackle too much while having it do its intended job, so there's no way they cam "work it out"

[bigarmzz]

Originally Posted by 1FaastC10

you cant really mess with the design of a shackle too much while having it do its intended job, so there's no way they cam "work it out"

"the "higher quality" lowering components have this worked out in there stuff"

well, i was actually talking more about the design of the flip kit and the angle to which its made to go on the rear....(i should have been more specific)

[1FaastC10]

this thread is about shackles, not flip kits.

[N2TRUX]

Originally Posted by 1FaastC10

this thread is about shackles, not flip kits.

And he was just trying to be helpful. Retract the fangs killer.....

[boxrodz]

Won't dropping the rear 2" with just shackles change the pinion angle enough to warrant shims? I figure 4" shackles will drop the rear 2", but also rotate the pinion about 4* downward. I figure by dropping the rear a couple of inches may also (just slightly) affect the angle of the tailshaft relative to the original pinion/tailshaft position. I'd think a 4* shim would correct the pinion angle. Maybe, someone who has done this can check the angle of the pinion and tailshaft.

[N2TRUX]

It's not just the amount of drop that determines if you need a shim. The amount of driveline angle that was already there is significant too. It seems that these trucks have enough angle that a shackle has little or no effect on them.

As an example of what I am refferring to, my 02 Harley F-150 had to have a shim with a 2" shackle because the driveline angle was almost flat to start with. If I had pics it might help clarify this...

[boxrodz]

I follow you regarding the driveline angle of these trucks. These trucks in stock form do have a significant amount of driveline angle.
But, I guess I was more concerned with the angle of the pinion in relation to the angle of the tailshaft.
Whenever altering the rear suspension, I though the angle of the pinion in relation to the angle of the tailshaft had to be preserved, i.e. the angle of the pinion equal (or nearly equal) but opposite to the angle of the tailshaft.
Using a shackle to raise just the rear portion of the leaf spring to obtain a 2" drop rotates the angle of the pinion downward.
For a 52" spring pack, I figure by just over 4*. To preserve the angles, the pinion has to be rotated upward 4* to match that of the tailshaft.
I believe the margin of error is around +- 1*.

Originally Posted by N2TRUX

As an example of what I am refferring to, my 02 Harley F-150 had to have a shim with a 2" shackle because the driveline angle was almost flat to start with. If I had pics it might help clarify this...

Gotcha.

[bigarmzz]

Originally Posted by 1FaastC10

this thread is about shackles, not flip kits.

wtf?...uh...yes it does...duh..

this thread is about gaining information about pinion angles as it would be directly related to lowering components in general...its hard to speak of just shackles when a question arises concerning a lowered vehicle

[piecesparts]

On our old Junky Chevys and not a ford, we have no problem with changing out the rear shackles. The only thing that you will have to do is cut the bed support bar so that the shackle will clear it. As I stated earlier, the Major designers sell these on a regular basis and do not include the shims. However, shims are easy to buy and install if that becomes the issue. I used to have to do that kind of work at the place I used to work. I presently have three trucks that I own that are lowered and there are no shackles in any of them. Also there are no vibrations, even at speeds greater than 80 MPH. I did the shackle only drop first and then went to the 4" drop with the front hangers, the systems are pretty self forgiving. I also have dropped a couple later model trucks 1991 and later with no ill problems on them. Go forth put the shackles on and try it.

[Kopper]

Just something else to throw into the discussion.

I believe that the 2-piece drive shafts are more prone to vibration problems when lowering the rear suspension than the 1-piece drive shafts are. With a two piece you can modify (raise) the hanger bearing to correct the angle.

[piecesparts]

Actually some kits send out a spacer setup for raising the rear of the tranny t align the shaft with the reaend in the other respect. It boils down to what ever you do to the rear end, you should analyse the driveline and it's geometry. This is not rocket science, or there would be a bunch of us country boys sittin' at the gas pump wonderin how it is done. GO FOR IT....

[boxrodz]

Thanks for the posts, piecesparts.
I'm just trying to cover the bases.
You're right, there is rhyme and reason to this.