Pacbrake Alpha XD Air Bag Suspension Kit Fitment with GM GR4 Suspension Option

Published 10/27/2026

Products Featured in This Question

Pacbrake Alpha XD Air Bag Suspension Kit - Rear Axle - 7,500 lbs

(16)

$693.08

Firestone Air Command Heavy Duty Air Compressor - Analog - Single Path

(393)

$521.49

Firestone Ride-Rite Red Label Extreme Duty Air Helper Springs - Rear Axle

(987)

$722.39

Question:

why does this kit not fit with rpo code gr4?

asked by: Ryan G

Expert Reply:

Thanks for reaching out Ryan. The installation instructions for the Pacbrake Alpha XD Air Bag Suspension Kit # PB77RV specifically state that it will not fit 2WD GM trucks equipped with suspension option code GR4, which identifies a 13,500-lb multi-leaf rear steel suspension. From what I was able to find, this suspension configuration changes the mounting geometry or available clearance for the air springs and brackets. However, Pacbrake doesn't specify exactly which component causes the interference, so I can't say for certain whether it's a spring mount, bracket, or another part of the suspension. One important thing to note is that the GR4 restriction applies specifically to 2WD models. Pacbrake does not list the same exclusion for 4WD trucks.

If you do have a 2WD truck with the GR4 suspension, another option worth considering is the Firestone Ride-Rite Red Label Extreme Duty Air Helper Springs # F56ZR. I reviewed Firestone's installation information, and this kit does not list the same GR4 suspension restriction. You can also pair these air springs with an onboard compressor like the Firestone Air Command Heavy Duty Air Compressor # F2097. This compressor is capable of producing up to 150 PSI, which matches the maximum operating pressure of the # F56ZR air springs.

What are you towing that has you considering adding air bags and what issues are you looking to fix?

expert reply by: Christopher H