I installed Firestone air helper springs on my 48 6400, but haven't used them yet.

Installed the same thing on my Dad's 05 F250, and they work as advertised, help keep the truck level with a truck load of Detroit Diesels in the back, about 4,000 lb. Also helpful for one trailer we pull with to much tongue weight.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-