Lowering Blocks

I want to lower my 1954 Pontiac 1 1/2" and that requires a lowering block. I have come up with a design for an axle mounting plate that places the 54 style shock mount in the correct location and accepts my new design lowering block. This allows any 76 era Firebird or Camaro rear axle to be bolted on to the original springs and shocks. No welding or frame modifying required.

parts car

1976 Camaro Parts Car

The lowering block mates the 1 3/4" spring to the 2 1/2" mounting pads on the Camaro differential. It also allows a wheel well centering range for the axle of 3" in 3/4" steps. This gives you the opportunity to center the axle in the wheel well up to 1 1/2" forward or backward from the axle center. The 54 axle mounting plates are offset by 1 1/2" (maybe 1 3/4") due to the original torque tube drivetrain. For some reason they had the plate mounting hole offset.

Here's a blueprint of the lowering block that I used. I machined it out of a solid 2.5"x2.5"x6" block of steel. I figure that you can make it easier out of 3 pieces: a 1.5"x1.812"x6" block and two side plates of 0.25" that are bolted together. It can be steel or aluminum. The drilled and tapped holes are for hex cap head bolts (5/16" NC18) for lining up the diff mounts. For some reason, the drawing package that I use didn't allow drawing hidden line circles, so I marked the two hidden circles with text and arrows.

Center spring mounts

Lowering block (note offset on spring) and custom shock mount

How's the fit?

The completed assembly bolted in perfectly. The Camaro rear end has the exact same mounting dimensions as the 54. Here's two vehicles 22 years apart and the widths are identical - talk about luck!

axle-spring centered

Here's the fit with the lowering blocks centered axle and spring

axle-spring offset

Axle set back 1 1/2" from spring

The lowering blocks were adjusted to set the axle back towards the rear by 1 1/2" to center (front/rear) the wheels in the wheel wells. The springs haven't had any load on them since rebuilding and I expect that they will flatten out once the engine is in and the vehicle goes for a ride. Should drop in height also.

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Copyright March 2011 Eugene Blanchard