I have a '79 FJ40 and need some help in clarifying shim installation instructions.
First off, let me say that I have Man-a-fre's steering correction / shackle reversal kit which comes with (2) shims - which appear to be 2 degree. Man-a-fre's directions say "Reinstall the leaf springs with the supplied caster shims, THICK SIDE TO THE REAR.
The Shackle Reversal Kit adds 1 1/4" to 1 1/2" lift. I purchased 2 1/2" front springs and 4" Rear springs in kit form from TPI (Smoky Mountain) in order to get an overall 4" of lift. I also ordered a pair of 6 degree shims as recommended for 4" lift kits.
The confusion comes in that the directions from Spector and others as well as this board say to install these caster shims with the THICK SIDE TOWARD THE FRONT!!
PLEASE HELP! I know up to 5 degrees caster is acceptable or even desirable with 4" of lift, and I know that caster is determined by the angle created by drawing a line through the knuckle bearings as compared with vertical. Also, I understand that the 5 degree caster is viewed from the side and is created by rotating the axle housing so the upper knuckle bearing is now rearward of the lower bearing.
The need for shims is supposedly created because of the axle housing rotation which comes from lowering the front leaf spring attachment by using a longer shackle which creates negative caster. Adding a shim with the THICK SIDE FORWARD then rotates the axle housing rearward and brings the caster back toward positive.
Does anyone have experience with the Man-a-fre kit and 4" lift? Do I use the shims as Man-a-fre instructs with THICK EDGE TO THE REAR, or should I use the 6 degree shims with THICK EDGE FORWARD? Would greatly appreciate any help and / or advise. Thanks very much.
Jim Dahlquist
Georgia Cruisers 4WD Club
First off, let me say that I have Man-a-fre's steering correction / shackle reversal kit which comes with (2) shims - which appear to be 2 degree. Man-a-fre's directions say "Reinstall the leaf springs with the supplied caster shims, THICK SIDE TO THE REAR.
The Shackle Reversal Kit adds 1 1/4" to 1 1/2" lift. I purchased 2 1/2" front springs and 4" Rear springs in kit form from TPI (Smoky Mountain) in order to get an overall 4" of lift. I also ordered a pair of 6 degree shims as recommended for 4" lift kits.
The confusion comes in that the directions from Spector and others as well as this board say to install these caster shims with the THICK SIDE TOWARD THE FRONT!!
PLEASE HELP! I know up to 5 degrees caster is acceptable or even desirable with 4" of lift, and I know that caster is determined by the angle created by drawing a line through the knuckle bearings as compared with vertical. Also, I understand that the 5 degree caster is viewed from the side and is created by rotating the axle housing so the upper knuckle bearing is now rearward of the lower bearing.
The need for shims is supposedly created because of the axle housing rotation which comes from lowering the front leaf spring attachment by using a longer shackle which creates negative caster. Adding a shim with the THICK SIDE FORWARD then rotates the axle housing rearward and brings the caster back toward positive.
Does anyone have experience with the Man-a-fre kit and 4" lift? Do I use the shims as Man-a-fre instructs with THICK EDGE TO THE REAR, or should I use the 6 degree shims with THICK EDGE FORWARD? Would greatly appreciate any help and / or advise. Thanks very much.
Jim Dahlquist
Georgia Cruisers 4WD Club