13" drum vs 11" drum wheel cylinders

[kdml]

Went to the auto parts store to buy new rear wheel cylinders for my '87 3/4 ton 4x4. They asked me if I had 13" or 11" drums. I have 13" and they said they only had the 11" in stock. The 11" looked to be the same size as the ones I pulled off the truck. Are there different size wheel cylinders for 13" vs 11" drums. I thought the only difference was SRW and DRW wheel cylinders (I have SRW).

Thanks
Doug

[mongocanfly]

I wasn't aware that 3/4t came with drw...

[kdml]

Greg,

I agree. I wasn't aware of a DRW 3/4 ton, but I believe both 3/4 ton and 1 ton came with 13" drums, which is the heart of my question. Is it the size of the drum which dictates the wheel cylinder or DRW vs SRW. Assuming I am correct that number of wheels dictates, then the 13" and 11" SRW may use the same wheel cylinder. That is what I am trying too confirm

Thanks

[mongocanfly]

im not at the shop or I could measure it for as I have both drw 1t and srw 3/4t 14 bolts.....I know on the srw the 16" rim barely fits over the drum...and I do mean barely...so I would think it would be 13....it sure cant be any bigger....

[Mattchu60]

I am pretty certain the 11" and 13" use different wheel cylinders. I believe the 13" ones are sightly larger.

[kdml]

Did a little more research online. Based on various parts store websites, the 11" drum wheel cylinder has a 1" bore and the 13" drum wheel cylinder has a 1-1/16" bore. I measured the bores on the wheel cylinders I removed and they are 1-1/16". I also measured the bore on the 11" drum wheel cylinder I picked up today and it also had a 1-1/16" bore. Went to the stores website and it specified the part was for replacement wheel cylinders with 1-1/16" bore. I am thinking I have what I need/

Thanks