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willysmjeeps.com :: View topic - M38 Brake Backing Plates
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M38 Brake Backing Plates

 
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RonD2
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Joined: Oct 02, 2014
Posts: 1889
Location: South Carolina, Dorchester County

PostPosted: Sun Nov 24, 2019 2:01 pm    Post subject: M38 Brake Backing Plates Reply with quote

I could use expert brake opinions please.

My left front backing plate has deformed and enlarged mounting bolt holes. At some point they were loose and wallowed themselves out. I'm pretty sure it's scrap and have acquired a pair of replacement plates. All are marked with part number 44917.

The bad one:



The replacement:



The slots on the tangs that the shoes ride and retract in on my bad plate are parallel to each other but on the replacement plates the slots are more "V" shaped. I don't know if this is just a difference in style, or normal, or due to wear and tear and they're also scrap? Can I use these plates with "V" shaped slots or will that cause problems?

I had no joy searching this point in the manuals or forums and could use your advice. Thanks!
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Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51

“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari

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wesk
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Posts: 16227
Location: Wisconsin

PostPosted: Sun Nov 24, 2019 9:15 pm    Post subject: Reply with quote

The illustration in 8012 page 282 looks like your v sahped unit. The illustraion in the ORD 9 clearly looks exactly parallel.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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RonD2
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Joined: Oct 02, 2014
Posts: 1889
Location: South Carolina, Dorchester County

PostPosted: Sun Nov 24, 2019 11:49 pm    Post subject: Reply with quote

Yes, saw that. Part of the reason I asked. And neither my original plate nor my replacement plate has the "drain hole" at the 6 o'clock position where it bolts up, as shown in the 8012 manual. The ORD9 refers to G503 part numbers for the backing plate. Once again, I'm not only fairly confused about what constitutes a worn out part, but also what is the "correct" part for a M38. Shocked

The shoes seem to fit up nicely with no slop or rattling.....
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Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51

“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari

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wesk
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PostPosted: Mon Nov 25, 2019 10:42 am    Post subject: Reply with quote

Quote:
Yes, saw that.
Then having seen the two illustrations I mentioned you should understand that production, demand, and existing supply stocks would be the the main factors influencing what was installed at the Willys factory and what was installed in the field. TM 9-803 (WWII MB) fig 85 pg 196 shows the very parallel slots and NO drain hole. My guess is you have one WWII plate and one 46-49 CJ plate.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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RonD2
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Joined: Oct 02, 2014
Posts: 1889
Location: South Carolina, Dorchester County

PostPosted: Wed Nov 27, 2019 10:52 am    Post subject: Reply with quote

Thanks Wes. Because both are marked with the same part number 44917, I'll assume it's just a style change from "V" slot shape to parallel slot shape for some unknown reason. By what you said, I'm guessing that plates with the 6 o'clock drain hole came even later after MB/CJ stocks ran out......

Main take-away answer to my question from what you said is that what I have isn't worn out --- so they're safe to use.

I don't recall seeing NOS backing plates anywhere, and nobody seems to be making new ones. Only used take-offs seem to be available, many in worse shape than others....
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Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51

“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari

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wesk
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Location: Wisconsin

PostPosted: Wed Nov 27, 2019 11:23 am    Post subject: Reply with quote

Quote:
Because both are marked with the same part number 44917, I'll assume it's just a style change from "V" slot shape to parallel slot shape

Wrong assumption. The parallel slot came first. Also the 44917 is the Bendix PN and early WWII were 44916 or WO# A450 then Late 44917 or WO# 800747. Also the Oct 1949 WWII Jeep ORD 9 shoes one more backing plate WO# A8898, GPW# GP2013, Bendix# 47054.
Eartly M38 were WO# 800747 which was superseded in Army supply system with WO# 641917. It is difficult to swear by any design features based entirely on part number or manual illustrations. The only place to get the bottom line answer is on the Willys or Bendix factory blueprints.

Quote:
Main take-away answer to my question from what you said is that what I have isn't worn out --- so they're safe to use.

I am not sure where in my posts you reached that decision but I cannot say weather they are safe to use or not without the blueprint or an NOS unit to compare worn dimensions to the original dimensions.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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RonD2
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Location: South Carolina, Dorchester County

PostPosted: Wed Nov 27, 2019 11:43 am    Post subject: Reply with quote

Thanks Wes. I understand reluctance to commit to a "safe to use?" question in a public forum --- that's my ultimate decision isn't it.

I'm just trying to understand yet another apparently obscure observation that I made: I have two plates, both marked 44917 from the same manufacturer, yet one has parallel slots and the other has "V" shape slots. Now I understand the "early" and "late" versions of the same part number. I understand why manufacturers don't ratchet part numbers when they make slight changes to a product when the original function remains unchanged. But that decision sure mucks up the parts manuals downstream doesn't it? At least it do for rookies like me.

All I really wanted to do was confirm that the "V" shape isn't due to normal (or abnormal) wear. It appears to me (in the absence of NOS or original blueprints to examine) that the maker made a change to his slot style for what remains an unknown reason. The only other possibility I can think of is maybe one of them is a counterfeit phony? Highly unlikely.

Based on the information provided, I'm going to use the "V" slot plates I have because I think they're serviceable and safe to use. I'm also fairly certain that the wallowed out mounting holes on my original plate aren't safe to use, can't be repaired, and it's scrap metal.

I appreciate your time!
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Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51

“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari

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wesk
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PostPosted: Wed Nov 27, 2019 1:02 pm    Post subject: Reply with quote

Quote:
Thanks Wes. I understand reluctance to commit to a "safe to use?" question in a public forum --- that's my ultimate decision isn't it.


Actually I am not displaying a reluctance to declare anything serviceable or safe to use on a public forum. I am not going to declare anything serviceable or safe to use anywhere without a sound basis for that determination.

For a fellow I thought to be in the avionics trades I am getting the feeling you must have an attorney background by the tone of your posts.

Quote:
Now I understand the "early" and "late" versions of the same part number. I understand why manufacturers don't ratchet part numbers when they make slight changes to a product when the original function remains unchanged. But that decision sure mucks up the parts manuals downstream doesn't it?

This has always been a problem in hobbies like this one. Most of us have gotten use to it and accepted it. Historical data always has a few missing pieces.

Quote:
All I really wanted to do was confirm that the "V" shape isn't due to normal (or abnormal) wear.

Many folks make uninformed decisions/choices based on available data or lack of available data. However in suspected metal wear cases it is also a good idea to include an examination for clear evidence of wear. The size of an opening can be enlarged by wear or design. To tell the difference one must use an examination method that includes using available industry standard knowledge of established metal wear patterns and evidence of suspected wear.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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RonD2
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Joined: Oct 02, 2014
Posts: 1889
Location: South Carolina, Dorchester County

PostPosted: Wed Nov 27, 2019 1:34 pm    Post subject: Reply with quote

Hi Wes,
Shocked There's no need to insult me. I was promoted out of hands-on avionics trades about 35 years ago. And no, not to become a lawyer. You have my apology if my "tone" offends you.

Being inexperienced with brakes myself, I thought I asked a reasonable question and could get a few opinions based on decades of experience out there. Something like "yes, I'd use that plate" or "no, don't do it!" with a "how come" or two thrown in would've been ok. Didn't think the conversation would devolve into killing the messenger.

I was thinking that passing experience and knowledge on is one of the purposes of this forum? Some days, maybe. Guess not today. Oh, well.......

Thanks anyway. Forget I asked. Have a nice day! Very Happy
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Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51

“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari

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