Swapping 13"x2.5" to 13"x3.5" drum brakes

[Dropped88]

Could you let me know your RPO code when you have time?

JB8

 

[1998_K1500_Sub]

As far as i can tell using a GM Parts Catalog and Rockauto's catalog, would need backing plates, shoes, and drums for JB8 single wheel, provided you didn't have any other worn parts and would only work on a 10.50 ring gear axle.

Did you actually find the parts on RockAuto's site (it sounds like you did)?

If you will, post a couple links or part numbers please. While this type of conversion is not in my cards now, I'm always interested in knowing what parts it takes to make it happen.

I did look earlier today on RockAuto and it wasn't perfectly obvious to me... OK, so I was in a hurry

 

[HotrodZ06]

The Backing plates are gm only and discontinued part numbers 15622343 lh and 15622344 rh, The Drums are gm part number 15633399 crosses to RAYBESTOS 2590R and BENDIX PDR0619 on rockauto, The Shoes are gm part number 12477878 crosses to RAYBESTOS 452PG and WAGNER Z656R on rockauto. Will probably need a new hardware kit as well, they are all listed as both 13x2.5 and 13x3.5 on rockauto. I looked everything up for a 98 with a 10.5 ring gear being mine is a 98 and still no guarantee it will all fit perfect until someone trys it. I plan to once I can source the backing plates.

 

[1998_K1500_Sub]

The Backing plates are gm only and discontinued part numbers 15622343 lh and 15622344 rh,

Are those backing plates specific to the 3.5" SRW drums on the 10.5" ring axle, or are they common to both the 2.5" and 3.5" SRW drums on the 10.5"?

Based on what you said earlier ("Would need backing plates as well as hardware") I'm assuming they're absoluately specific to the 3.5" drum but I just want to confirm.

If so, then finding the donor truck is the hardest part of the swap.

 

[xXxPARAGONxXx]

I'm reading another site which seems to suggest that the 9.5" SF and 10.5" FF axles have the same diameter axle tubes: 3 3/8".

On the other hand, check out this post:

8 lug SRW brake backing plates same as 14 bolt six lug axle??

Does anyone know where I can buy the 13x2.5" 6 lug complete rear drum brakes? They are hard to find around here. Next thought is, are the 8 lug SRW backing plates the same as ^^^ if yes I can get the drums and the rest new.

www.thetruckstop.us

So, it doesn't look like it's possible unless someone wanted to do custom fabrication (somehow). In the end, it would probably be better to just swap in a 14-bolt full-float axle.

 

[HotrodZ06]

Yes the backing plates drums and shoes are the only 13x3.5 specific parts I found while looking the hardware kit shows to fit both on rockauto no gm part number to verify but i always need new hardware lol.

 

[stutaeng]

Are those backing plates specific to the 3.5" SRW drums on the 10.5" ring axle, or are they common to both the 2.5" and 3.5" SRW drums on the 10.5"?

Based on what you said earlier ("Would need backing plates as well as hardware") I'm assuming they're absoluately specific to the 3.5" drum but I just want to confirm.

If so, then finding the donor truck is the hardest part of the swap.

Um, maybe this is specific to the 10.5" axle then?

The C/K2500 BBC/Diesels also got the 10.5", but I don't know what brake RPO code they got?

Otherwise, if parts are obselet an axle swap is perhaps an option to the OP?

 

[HotrodZ06]

The problem with the 9.5 ring gear axle is the hub is made to the axle the 13x3.5 drums won't fit to my knowledge. But I could be wrong.

 

[stutaeng]

...axle swap, along with associated brakes...

 

[HotrodZ06]

Um, maybe this is specific to the 10.5" axle then?

The C/K2500 BBC/Diesels also got the 10.5", but I don't know what brake RPO code they got?

Otherwise, if parts are obselet an axle swap is perhaps an option to the OP?

That is how I would understand it. Mine is a 98 k2500 350, NV4500, 10.5 ring gear with 13x2.5 (JB7) brakes. I think 3500 single wheel trucks and possibly 2500 suburbans came with 13x3.5 (JB8) brakes.