The Stovebolt Site Forums The Shop Area General Truck Talk Rear wheel cyls on '40 GMC

Does anyone know what the stock rear wheel cyls are supposed to be on a 1940 GMC 1/2 ton? My rears are different than my fronts. I just sandblasted the rears and they are Delco 1" with a casting # of "6463" with a physically larger # of "820" cast on the body as well. I'm thinking that my rear diff., axle housing, etc. has been changed out, although the wheel bearings and seals that I ordered from Jim Carter are the right ones. Everything else on the rear end looks exactly like it should; e-brake openings in the backing plates, etc. I bought new wheel cyls like the fronts, except 1-3/16" dia. (typical for the Huck brake system) but they don't fit the opening or bolt pattern in the backing plate. Does all of this make sense? If I'm going with these Delco wheel cyls, where's a good place to buy rebuild kits? Thanks for your help.

NAPA can get you the complete wheel cyclinder. It makes sense. .Sometimes you have too modify.also they have all the parts for the breaks.Don,t use old junkyard brake parts.Saftey first.ya don't want to loose all that hard work,when ya can't STOP.O'MY

NAPA or CarQuest should be able to get them for you.

I,ve got an old Napa brake parts catalog. The rear brake is shown as 1 3/16. 51 up are 1 in. but that is for bendix brakes. The part no. for the 1 in. rebuild kit is #21. The new cylinder 51-55 first is 14497.
I,m going to make it to Bend Or. one of these days. George

Thanks for the info guys. I went to Napa and they had 2 rebuild kits in stock at $7 and change each. Bought 'em both. I just wish I knew why my presumably stock rear end has different wheel cyls. I actually need all of the brake mounting hardware for the pads, etc. Time to visit the junkyard, I guess.

And George, if you ever get to Bend I hope you give me a holler. It's a beautiful town full of friendly people.

If your 40 is anything like my 46 then the front and back brake cylinders ARE different. I don't remember the sizes right now but the fronts are larger than the backs. Sounds to me like you have the orig rear end.

As for the mounting hardware you might be able to get that at NAPA also. You might have to search their old books and look at some pictures to get what you need.

Good luck
George

Well, I've got totally different wheel cyls on front and rear. The fronts actually seem alot beefier that the rears. At this point I've decided to go ahead and use what I've got on the rear. They're 1" Delco, as opposed to 1 -3/16" that apparently came stock. I also just realized that these 1" Delcos don't have any way to be adjusted!! Does that sound right too you guys? The ends of the cyls themselves are just black rubber "covers", for lack of a better term. The front cyls have the metal end caps that you can rotate and move the screw out. This is getting frustrating! :mad:

Your rear end is a latter model & uses Bendix style brakes. You are going to have to use 51 up brakes parts on it.

somone probably put a different model rear end under your truck. When these trucks were still in general use people didn't care about matching numbers or anything else. The only question was would it work, and they used anything that would. I have a 53 model 6400 with what I think is a 48 rear end under it.