Greasable Rear Spring and Shackle Bushing Kits for GM Trucks
We are working with a second generation Kevlar reinforced polyurethane bushing material that is proving to be another step stronger and more durable. At this time the new material is only available in the same grey color as our Kevlar tierod end boots. For more information on bushing color, click here.
Fourwheeler Magazine's Project "Stinky" gained 50 points on the test ramp and about 1 ½" of rear shock travel just by replacing the shackle bushings. These work! Drilled and crossdrilled grade 8 bolts and sleeves and channeled bushings allow you to lube your poly bushings for better ride, less wear and eliminate bushing "squeak".
A often misunderstood fact is that factory rubber bushings offer less flexibility than aftermarket urethane. Most people have heard or read otherwise but rubber does not work as well in the real world. The reason is that the factory rubber bonds the inner sleeve to the outer sleeve and spring. Since they're bonded together, the inner sleeve can't twist relative to the spring. When you tighten your shackle and spring bolts the inner sleeve is locked solid to the vehicle so the suspension is limited by the rubbers inability to rotate. Urethane bushings on the other hand, can rotate freely around the inner sleeve and will not bind up the suspension.
Looking to add our Kevlar bushings to your leaf springs but don't know your spring eye ID? Here is a quick way to find out without pulling apart your truck.
Measure the OD of the spring eye,
in this case 2"
Then measure the thickness of the leaf 1/4" on this truck.
Now subtract 2 Xs the thickness from the spring eye OD
2 x .25 = .5
2" - .5" = 1.5"
So this spring needs 1.5" bushings.
*Make sure to do this on each spring eye because they can be different
Shackle bushing size: Most '80 and older Chevy trucks use a 1-1/2" shackle bushing. Most '81-'87 1/2 ton Chevy trucks and '81-'91 1/2 ton Suburbans and Blazers used a 1-3/8" shackle bushing. Most '81-'87 3/4 ton Chevy trucks as well as '81-'91 3/4 ton Suburbans and K30's use 1-1/2" shackle bushings. Spring eye size: 52" rear springs came in '67-'87 1/2 ton GM trucks, '69-'91 Blazers, most 1/2 ton '67-'91 Suburbans and rarely in '73-87 3/4 ton pickups. Most use 1.5" bushings at each spring eye, but the '88-91 Blazers and Suburbans could have 1.5" or metric (~1.7") spring eyes. 56" rear springs came in the rear of all '76-'91 K30's, most '67-'87 K20's, most 3/4 ton Suburbans and rarely in 1/2 ton Suburbans. Most use a 1-3/4" bushing at the front and a 1-1/2" bushing at the back, but we have seen sets that had 1-3/4" eyes at both ends and metric (~1.7") eyes at both ends. If the eyes are different sizes, they should be 1-3/4" and 1-1/2", if they're the same size you'll need to measure. 64" springs from an '88 and newer GM trucks have become a popular swap. The '88-'98 springs use a 43mm metric spring bushing at each end. At this point we do not have bushings for '99 and newer springs. 8" Superlift rear springs use a unique bushing.