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Cj2A master brake cylinder

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Thing 2 View Drop Down
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    Posted: 10 June 2018 at 6:51pm
my 46 CJ2A needs a new master cylinder. If I give you the VIN number ( 63563 ) can you tell me which one to order. Two choices are: #1 front mounting hole is threaded. Or #2 both front mounting holes are not threaded, goes straight through. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ndnchf Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2018 at 7:24pm
According to Walck's its this one:

But why don't you just look and see what is on it now? That would eliminate any guess work. No telling what has been changed over the  last 72 years.
1948 CJ2A - It goes nowhere fast, but anywhere slow!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Thing 2 Quote  Post ReplyReply Direct Link To This Post Posted: 13 June 2018 at 8:39pm
I found out that you can determine which kind of master cylinder you have by measuring the bolt distance c/c. If it’s 3.25” your master is the “ front mounting hole is threaded “ variant. The other variety is straight through and wider c/c than 3.25”. Now, I still have to drive 155 miles to inspect the thing. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ol' Unreliable Quote  Post ReplyReply Direct Link To This Post Posted: 13 June 2018 at 9:15pm
That's some useful info.  Thanks!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce W Quote  Post ReplyReply Direct Link To This Post Posted: 13 June 2018 at 11:29pm
Do they break it down into "early" vs "late"? If so, I'm sure you need the early one, I don't think that was changed until the frame was changed in '49. Or you can check and see what the CJ3A/B call for. I'd bet that they use the same as the "late" CJ2-A. You would need the other one.   BW

Edit: I just checked the parts manual. The "early" master cylinder is part # A-556, and is used thru serial number 215649. Part # 647558 is used on "late" CJ2-A's after serial number 215649, and all CJ3A's. An aluminum master is mentioned for the later models, which I've never seen. 
  If you would like, I can measure the bolt center distance on one of my '47s tomorrow.    BW
Happy Trails! Good-bye, Good Luck, and May the Good Lord Take a Likin' to You!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote WeeWilly Quote  Post ReplyReply Direct Link To This Post Posted: 14 June 2018 at 9:07am
The master cyl. bodies are also different in shape between the early and late. The early has a round tube like shape to the reservoir  while the late has  more of a square shape to it.

   Jim
47 CJ2A (Ranch Hand) 48 CJ2A, 48 Willys truck, T3C 3782, M274 (Military Mule)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tufcj2a Quote  Post ReplyReply Direct Link To This Post Posted: 14 June 2018 at 8:14pm
Yes, I just replaced my MC, very easy to tell the difference. Just take a look  at the frame and you can usually tell immediately.  One version bolts through the frame, the other bolts into it.

otherwiseee measure from bolt to bolt.
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