The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 55.2-59 1959 got bigger brakes... since when?

1project2many · 05-05-2021, 08:20 PM

Long story short, it looks like the secret is the backing plates. If a guy wanted to run 2" rear brakes he would locate a set of backing plates from a '59 through '75 GM (not Dana) 1/2 ton rear axle.

1" diameter wheel cylinders 5465039 (L) and 5465038 (R) fit '55 - '72 1/2 ton non-posi trucks.
http://www.gmpartswiki.com/getpage?pageid=22337

Backing plates # 3984867 (L) and 3984868 (R) fit 1/2 ton non-posi axles from '59 up to '75.
http://www.gmpartswiki.com/getpage?pageid=22391
http://www.gmpartswiki.com/getpage?pageid=61101

These plates go through a series of number changes along the way to the numbers above:
L 3775369 --> 3840929 --> 3896883 --> 3984867
R 3775370 --> 3840930 --> 3896884 --> 3984868

For daveshilling and anyone else who happens to get a '58-'59 Chevy with Dana / Posi axle, backing plate #'s are: L 2346817 R 2346816

I also stumbled on an interesting part number for the guys with 2" rear brakes. Self adjusters were installed by GM beginning in '63 on cars and '64 on trucks. A "Self adjuster kit" 3826517 was available from GM to convert '59-'62 cars and '59-'63 trucks to the later configuration.
http://www.gmpartswiki.com/getpage?pageid=66808

A GM service bulletin for this kit describes "new" self-adjuster operation, has part numbers, and describes the installation procedure. Reading through the procedure it seems as though a person with 1 3/4" brakes, following the same steps and using the equivalent parts from a set of 2" brakes, could install self-adjusters on the rear of an older truck. And since the front brakes already have 2" shoes, it stands to reason they could also be upgraded. The bulletin can be seen here: https://www.corvair.org/chapters/cor.../S-AB/S-AB.pdf

And for anyone who just needs a set of shoes, Napa is showing 11 X 1-3/4 rear shoes up to '57 and 11 X 2 after that. TS9 is listed for the 55-57 rear and UP228 (there are fleet shoes available also)for the '58+ rear and '55-'59 front shoes. With all the overlap, if I owned a '58 or a truck that may have received an axle swap I'd probably measure shoe width before ordering new shoes.

05-05-2021, 08:20 PM	#13
1project2many Registered User Join Date: Mar 2012 Location: Lakes Region NH Posts: 3,158	Re: 1959 got bigger brakes... since when? Long story short, it looks like the secret is the backing plates. If a guy wanted to run 2" rear brakes he would locate a set of backing plates from a '59 through '75 GM (not Dana) 1/2 ton rear axle. 1" diameter wheel cylinders 5465039 (L) and 5465038 (R) fit '55 - '72 1/2 ton non-posi trucks. http://www.gmpartswiki.com/getpage?pageid=22337 Backing plates # 3984867 (L) and 3984868 (R) fit 1/2 ton non-posi axles from '59 up to '75. http://www.gmpartswiki.com/getpage?pageid=22391 http://www.gmpartswiki.com/getpage?pageid=61101 These plates go through a series of number changes along the way to the numbers above: L 3775369 --> 3840929 --> 3896883 --> 3984867 R 3775370 --> 3840930 --> 3896884 --> 3984868 For daveshilling and anyone else who happens to get a '58-'59 Chevy with Dana / Posi axle, backing plate #'s are: L 2346817 R 2346816 I also stumbled on an interesting part number for the guys with 2" rear brakes. Self adjusters were installed by GM beginning in '63 on cars and '64 on trucks. A "Self adjuster kit" 3826517 was available from GM to convert '59-'62 cars and '59-'63 trucks to the later configuration. http://www.gmpartswiki.com/getpage?pageid=66808 A GM service bulletin for this kit describes "new" self-adjuster operation, has part numbers, and describes the installation procedure. Reading through the procedure it seems as though a person with 1 3/4" brakes, following the same steps and using the equivalent parts from a set of 2" brakes, could install self-adjusters on the rear of an older truck. And since the front brakes already have 2" shoes, it stands to reason they could also be upgraded. The bulletin can be seen here: https://www.corvair.org/chapters/cor.../S-AB/S-AB.pdf And for anyone who just needs a set of shoes, Napa is showing 11 X 1-3/4 rear shoes up to '57 and 11 X 2 after that. TS9 is listed for the 55-57 rear and UP228 (there are fleet shoes available also)for the '58+ rear and '55-'59 front shoes. With all the overlap, if I owned a '58 or a truck that may have received an axle swap I'd probably measure shoe width before ordering new shoes. Last edited by 1project2many; 05-05-2021 at 08:40 PM.