Lost brake booster part?

[idrivejunk]

Working on a 1970 Mach1 with a single diaphragm Bendix power brake booster #6945. When I separated the master cylinder from the booster on a bench, I must have lost something. I didn't unclip anything and thought I was being wary for falling parts, but as soon as I pulled it I passed it to our paint shop. I think I have the pushrod (goes between master and booster) but am missing the "reaction disc" and possibly a plunger end that rides on the pushrod at the booster end. Theres nothing rattling around inside the booster but I think I will use a scope tool to look inside when I get back to the shop Monday. Didn't think of that while I was there!

I don't have the chassis assembly manual and cannot find any help from web searching and am almost to the point of wanting to buy a booster / master combo just to see whats in between. Just don't know what I am looking for, heck it may have fallen out on the bench and I just don't know what it looks like. Anybody got a diagram, pics or part numbers, or just a helpful hint? Thanks in advance.

Any help would be greatly appreciated. Here are a few pics to illustrate my problem. I can imagine what the piece must look like that sets in the booster before the pushrod and master cylinder are installed, but thats all I can do at this point. It should be a round rubber wafer and a thicker piece over that, from what I've been able to find out.

[enjenjo]

It looks like the whole piston assembly is missing.

[idrivejunk]

It looks like the whole piston assembly is missing.

If I only knew what it looked like, I might have a sportin' chance at finding it. Can't have gone far. I have looked real hard for things that might be it but theres so many bits and pieces about  

[enjenjo]

The part you are looking for is steel, round, about 7/8" diameter, and about 5/8" long. It will have a hole part way through the center slightly larger than the pushrod. There is a rubber washer/Oring that hold the pushrod into the piston. There is also a rubber sealin most of them that fits on the flange in the center of the front housing.

My best description, it looks like a charging piston for a M3 machine gun, but I am sure that is not much help.

I could not find a picture so far.

[idrivejunk]

Hey thanks, that helps more than you know. I didn't know if it might even be plastic. All the cutaway views I see show a rubber pad on the end, but the piston shape varies. I thought it might fit into that hex shaped area but now I think it will be round and bottom out in that round well area. Maybe I should concentrate my search in the area where the unit was prepped for paint. My only thought is that it could have fallen into the booster then been unknowingly dumped on the floor during prep. Maybe someone picked it up thinking "this goes to something" and put it on the corner of a bench. Thats gonna take some luck. Too bad, I've got the assembly manuals for interior, electrical, and body but no chassis. Hence my lack of a clue.

Oh and I'm up to speed on Garands, carbines and M-14s but not M3s! Dang.

[idrivejunk]

Just a follow-up. We ended up locating a reman booster/master unit and all is well. Many other parts were missing from the existing booster, I think it was just there for looks. I didn't lose anything after all. Someone had made a longer pushrod that pretty much pushed thru the booster to work the master, so not only was the old booster incomplete and probably bad, but there was no assist actually happening. Should have good power disc brakes when I finish, but I was lost until I saw a complete unit. The booster end of the pushrod looks nothing like I had imagined.

Thanks for the help, enjenjo!