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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
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| | | | Joined: Sep 2012 Posts: 13 New Guy | | New Guy Joined: Sep 2012 Posts: 13 | How do all, I need a new "rubber" diaphragm for my 2 speed rear end. It's probably original. And is cracked and leaking. I found a new seal for the piston. Which used to let 90 weight be sucked into my motor.Scared the crap out of me cuz I have a brand spankin new 235-250 now that was blowing white smoke at start up. Figured it out tho. But need the new rubber and don't know who might have?
1949 chevy 6400
2 ton
2 speed rear end
| | | | | Joined: Mar 2011 Posts: 39 Wrench Fetcher | | Wrench Fetcher Joined: Mar 2011 Posts: 39 | I looked everywhere for mine and the only thing I could find was the complete unit for like $300. So I got a inner tube for a lawnmower and cut a circle out of the outer part that touches the tread so I had a round dome shaped piece and use that it works great. | | | | | Joined: Sep 2012 Posts: 13 New Guy | | New Guy Joined: Sep 2012 Posts: 13 | That's very cool. And I am that type of guy as well. Good idea. Cuz I was thinking about what I was going to use that had some cyrvature to it. Thnx Bud! | | | | | Joined: Apr 2007 Posts: 1,038 'Bolter | | 'Bolter Joined: Apr 2007 Posts: 1,038 | The diaphragm part number is 3847058. This part was used on early 70's trucks and thus can be still obtained at GMC parts departments. You may have to ask them to use their obsolete parts locater computer. I was able to get a brand new one from a GMC truck center in Phoenix.
Kent | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | Inner tube mat'l is not neoprene, might not last very long in that application.
Last edited by EdPruss; 12/04/2012 10:32 AM.
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Nov 2010 Posts: 1,159 Shop Shark | | Shop Shark Joined: Nov 2010 Posts: 1,159 | I used a double-layer of "boot"material(22"inner-tube liner),for my application. I re-built one back in the '80's,and it lasted until the truck,('60 Apache 60),got so badly rusted,that when you applied the brakes,the cab would shift and the gas pedal would jam to the floor! Wasn't long b-4 that poor tired old 283 threw a rod at a stop-light! Wasn't neoprene,but it lasted 10 years with about a million splits in that amount of time. I hauled a lot of building material,and roof tear-off's with that old girl. | | | | | Joined: Aug 2012 Posts: 12 New Guy | | New Guy Joined: Aug 2012 Posts: 12 | I'm going to toss this out-- I've not tried it, but it's a thought.
How about the diaphragm from an air brake chamber. They come in a lot of different sizes. Maybe one of them is the correct size?
I know they are tough- I've cut a couple up to make rubber seals for something else. | | | | | Joined: Feb 2010 Posts: 476 'Bolter | | 'Bolter Joined: Feb 2010 Posts: 476 | Try obsolete chevy 1-800-2488785 I'm pretty sure they have them. I thought I needed one but disassembled mine, pulled it with a vise grip a few times, rubber looked good, reassembled and it's worked fine. | | |
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