M1008 brake master cylinder

I need a brake master cylinder for my 1985 m1008. Is it the same as a civilian k30 with a 6.2 or is it a military specific part? i remember reading on the old site in the pm articles that there is a difference in the m1008 and m1009.

When i've gone after master cylinder replacements before, when i didn't know the RPO codes or the correct part number in advance, the deciding factor has always been the size of the brakes. Specifically, "usually" the size of the rear drums. I've never owned a vehicle with rear discs. That being said, i would GUESS that the part for the M-1008 would be the same as a civilian K-30 with the big rear brakes. I do not remember the RPO code, but the size sticks in my head as 13"X3 or 3-1/2". As i believe all of the 30's had hydroboost, there shouldn't be any difference between gas or Diesel trucks. Again, GUESSING here, but the M-1009 should be a different part from the M-1008 because of the different rear brake sizes. My TM's are not currently available to me, but i seem to recall that one or more of them showed GM part numbers for a lot of this stuff. You could compare that information. My local NAPA guys seem fairly proficient at digging up this stuff, and lately they don't have much else to do, so they fall all over themselves to help me spend money.

Yes, it's the same as a civvie 1985 K30 with a 6.2

Later,
Joe

Well I know this is an old thread but my Master Cylinder on my 1985 airforce m1008 has been changed at some point not sure if its right one on the truck( due to just checking the rear brakes for the first time and the shoes were on backwards from a previous owner) it doesn't have the stamp#number #1605 or #1925 that napa and others ask for.So my question is how do I get the correct one and whats the difference between the 2 I have a number I got off the bottom of my master cylinder its 31202231538 I think its a bendix but I cant get this number to cross.So anyone know the original GM number for the correct one and what the diffrences are between the two stamped numbers.I would be grateful for any help or insight.Thanks

SouthernSteel said:

Well I know this is an old thread but my Master Cylinder on my 1985 airforce m1008 has been changed at some point not sure if its right one on the truck( due to just checking the rear brakes for the first time and the shoes were on backwards from a previous owner) it doesn't have the stamp#number #1605 or #1925 that napa and others ask for.So my question is how do I get the correct one and whats the difference between the 2 I have a number I got off the bottom of my master cylinder its 31202231538 I think its a bendix but I cant get this number to cross.So anyone know the original GM number for the correct one and what the diffrences are between the two stamped numbers.I would be grateful for any help or insight.Thanks

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The GM number should be in the parts TM.

Well Thanks for that info made my day :] I can never figure out the right TM which one would have the diagram and part number if you don't mind me asking.

SouthernSteel said:

Well Thanks for that info made my day :] I can never figure out the right TM which one would have the diagram and part number if you don't mind me asking.

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The parts TM's end in P as in either -20P or -34P

Also something to consider. All CUCVs regardless of year, were made to the 1984 specs. There is a little exception with the rare 1987 models. If you need parts common from a parts store, shop for a 1984. Here is a link to the VIN card to help you know more than the parts guy.
http://service.gm.com/dealerworld/vincards/pdf/vincard84.pdf

TMs. Yes they can be confusing. If you don't invest the time to learn how they are laid out, you lose out on much good info. Once you do learn them, you can find information such as the master cylinder PDQ without having to rely on someone else to do your legwork. I used to search the TM's for everyone all the time. Once I started realizing that most folks felt their time was more important than mine, I quit looking.

"Also something to consider. All CUCVs regardless of year, were made to the 1984 specs. There is a little exception with the rare 1987 models. If you need parts common from a parts store, shop for a 1984. Here is a link to the VIN card to help you know more than the parts guy.
http://service.gm.com/dealerworld/vi.../vincard84.pdf"

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Thats an interesting tidbit of info.

First off I don't think anyones time is worthless.Second of all im in a time constraint and I was asking for help i have been on here long enough to know what a TM is im fighting a losing battle with my M1008's but that's a whole different thread on its own.As simple as it is for all of you to look in the tm i don't have a lot of time to devote at this point to reading them to completely understand them.Im far from lazy im pretty mechanically inclined 99.9 percent of the work to my m1008 im very frustrated at the moment and i was hopeing to get the GM part number for the Master Cylinder so i can fix my truck.Not to be rude or snarky about this steel soldiers has been a great help to me and i have learned a lot.I do not get on here and ask a question very often,Unless im in dire straits which at the moment i am,Im use to the smart remarks (i deal with the Public)I normally take things with a grain of salt and let it roll.I asked a simple question and got 2 smart remarks which is fine.I was hopeing that some one would help and be nice,I looked through the 2 tms mentioned and i only saw everything but the part number for what i was looking for.(DOGHEAD i know the game lol the minute i post this you probably found it in 2 seconds) Haha Guys Look im not mad nor am i upset im just very frustrated and i was hopeing for a break instead of wasteing time.I have been unemployed for over 2 years and i have a lot going on more so than the average person its been rough and im not going into details.But im really close to finally going back to work enough about that no one wants to hear a whiner.Yall have a great day tomorrow and i will dig through the millions of pages of the tm and try to figure out how to read them.

My computer that had the TM's downloaded crashed , so I don't have them right now and it takes way to long to open them not having them saved to my computer ( the one I'm using isn't mine ). But the master cyliner part number is in the -20P TM go to the index page scroll down till you find the brakes section , there will be a red box around page numbers click on that and it will take you to that section . Then scroll through that section till you get to the diagram with the master cylinder on it , then scroll up or down to the parts list take number ( 20 or something close for the master cylinder) <there will be 3 rows of numbers the the description of the part . The 3rd number is the part number at the top of the collum it says part. That will be the GM part number. If you have the TM's saved to your computer it should only take a couple minutes to find it.

What I found on 20-P. There are 2 different ones listed. #30 is part # 2232073 and part #34 is 2232072. When I used those part #'s to try to find the part I couldn't find that part for sale. I hope this may help you.

This one may work-
[h=1]Dorman M39435 Brake Master Cylinder[/h]

Okay here is how to read the TMs. This applies to all the MVs

1 - First you have to decide which of the vehicles you are working on. M1009, M1008, M1028, etc
2 - Then you have to lookup the UOC (Usable on Code) for that vehicle. The UOCs are listed at the beginning of the manuals
3 - Then you lookup the part for that UOC

Some parts are universal across the series and some are unique to the type of vehicle.

So for your M1008 the manual lists the UOC as 194

Looking at the parts diagram in the TM 9-2320-289-34P parts manual for the master cylinder we find the picture listed as Figure 117

It shows two M/Cs, part #30 and #34.

Scrolling down you will find an entry for part #34 and #30

#34 has a UOC of 209 - That is the M1009 blazer. It isn't the right one

#30 has a UOC for all the other trucks. This is the one you are looking for

The CageC( manufacturer) code is 14892 (which is General Motors). The GM part number is 2232073. The NSN is 2530-01-156-7016

Googleing the part number comes up with nothing. So we will have to look the NSN number up on www.partstarget.com

NSN 2520-01-156-7016 comes up with a few different part numbers

http://www.parttarget.com/2530-01-156-7016_2530011567016_2232073.html

14076814
2231925
2232073
2530011567016

Now looking at all the different parts sites for a 1984 K30 6.2L master cylinder they show a couple of different ones with a "stamp" on the bottom, a "#1605" and a "#1925"

Looking at those numbers and and the possible part numbers, I would say that the #1925 is the M/C you want

Of course YMMV

Wow, this makes me tired. For something as simple and cheap as a MC, get both listings and return the one you don't need. These rigs are 30 year old. You are lucky if the reman exists, you are really lucky if it fits without refitting the brake lines. If you are really cheap, just get the rebuild kit and use your OEM MC on the truck.

There...I just saved you a lot of hassle!

I would suspect that a LOT of parts still are made for these trucks, even though they are 30 plus years old. Chevy made a crap load of them over the years.

You can still get new master cylinders for the old 62 GMC. As many millions if not close to a billion of these trucks made, parts will be around for a spell.

Thanks for the info everyone.I hope I can figure out my braking system.I have replaced the rear shoes,Front Pads,New Brake calipers,New rotors,Front wheel bearings,New hoses front and rear.The master Cylinder and the 2 proportioning valves are all I haven't changed and the Truck still has a pulsating as I slow down from about 45mph and it feels like the shoes or pads are still dragging when you try to use the full braking of the system it shimmys the steering wheel goes left and right if you ease on the brake pedal it doesn't do it.Either Master Cylinder is bad or the rear drums are warped (BTW a tid bit of info when we bled the brakes the first time when I replaced all the brake parts on the front we had a bit of time getting fluid to the pass side front not sure if that explains anything maybe some insight I would be greatful. Thanks Ahead of time everyone.



Btw.Skinny my issue was that the master cylinder isn't the original one hence me asking about the GM number and the #1605 and #1925 stamp i wasn't sure if the right one was on the truck after we checked the rear and the rear shoes were on backwards hahah so i have my doubts and im willing to correct the problem as I love the trucks.:]

I know all the stuff up front is new, but it sounds like a warped rotor or loose wheel bearing. It does NOT sound like master cyl. or rear brakes. I jack up the front and 'wiggle' the tire up & down, left & right. That will tell you if you any play in king pins, wheel bearing or tie rods. If thats all tight I'd pull a wheel and check the rotors.

Its not that checked that New rotors from napa and Timken front bearings both sides when the rotors got done. it seems to only pulsate as I brake the more pressure I do on the brake pedal the worse it gets and as you slowing down almost to a stop its a forwards backwards movement like something is still grabbing the truck has always acted funny but it seems worse now.Could the rear proportioning valve be bad?


Btw Tie rods and Drag link are all new not even a year old

I wouldn't think a Caliper was hanging up again but I suppose anythings possible.