GMC Air pak database

[SturmTyger380]

Here is what I have found and GunFreak might have seen this too. Except for the hydraulic outlet fitting size the 2500690 looks the same as the 2500685.

The outlet fitting size went from 5/18 to 1/2 inch. Not a big change. Since the other main parts stayed the same I would think the output pressure would be the same. From what else I read it looks like the 690 model was the natural successor to the 685 and was used in vehicles like Ford and IH from the 1950's through the 1960's

Alan

 

[1Pinkerton]

BSI told me to send them my airpack and they’ll rebuild it for $480.83

 

[M221Jimmy]

BSI told me to send them my airpack and they’ll rebuild it for $480.83

I just rebuilt my airpack, took a little time but nothing to hard. I think I have about $470 in it ($300 new cylinder bore, small piston and cups from Classic and Exotic Restorations/ $30 machine work on small piston housing/ $140 Ebay 5-ton rebuild kit) and it works well. If the bore wasn't pitted and could have been honed I would have saved $200. But I'm happy, I have brakes and I have a through understanding of the units operation and potential issues.

JT Melcher

 

[m1010plowboy]

That's a fair price. Is that the route you're going? I wonder what they're planning on doing for the seals and wee piston.

The collector hobby guys would really like "Repair Kits" put together so we can do them ourselves. Putting thousands of man hours and dollars into the MV's for events, parades, history preservation means if I can save a few hundred on labour, I can put it in the fuel tank.

If BSI has the parts and pieces to put one back together, could we ask if they have the parts and pieces for 10 more? The market size is a hard number to guess but I see 10 units that could use a fresh air-hydraulic cylinder while one is on the bench being rebuilt. With some broad market exposure, maybe we could reach twenty? G749 owners that want ' repair kits '.

Thanks for the info, let me know if we can help follow that up or if your contact at BSI might give you some repair details.

 

[1944mb]

I used a 5 ton repair kit from Eastern surplus. USMC was able to machine me a 5 ton piston and viola. Paul machined me a piston as prototype(it was an exact 5 ton setup)-it worked perfect.

That's a fair price. Is that the route you're going? I wonder what they're planning on doing for the seals and wee piston.

The collector hobby guys would really like "Repair Kits" put together so we can do them ourselves. Putting thousands of man hours and dollars into the MV's for events, parades, history preservation means if I can save a few hundred on labour, I can put it in the fuel tank.

If BSI has the parts and pieces to put one back together, could we ask if they have the parts and pieces for 10 more? The market size is a hard number to guess but I see 10 units that could use a fresh air-hydraulic cylinder while one is on the bench being rebuilt. With some broad market exposure, maybe we could reach twenty? G749 owners that want ' repair kits '.

Thanks for the info, let me know if we can help follow that up or if your contact at BSI might give you some repair details.

 

[USMC 00-08]

I did play around with duplicating a 5 ton piston out of 304 stainless. Now that we know it works, I should probably make some more here soon.

 

[USMC 00-08]

Here is an interesting article on airpak maintenance.

View attachment Airpak Maintenance.pdf

 

[DavyBoySmith]

Hi guys, I got an order in for newly manufactured air-pack Control Valve Piston Seals (the ones for the G749 M211/M135 not included in the M54/M809 rebuild kit)
They are essentially identical to :
Part Number 374272 for the hydraulic side of the piston, and
Part Number 375833 for the air side of the piston.

I will be offering these for $30 for the pair These are new, New Manufactured parts not New Old Stock.
The dies are being manufactured by a United States hydraulic seal manufacturer established 50 years ago and will be made on equipment in their facility.
The NRE on the dies was a bit pricey but only a single set of dies is required as the 2 seals are identical in size and shape the only difference between them is Shore Hardness (Durometer) and material (one is resistant to brake fluid, DOT3/DOT5 Silicone, the other is resistant to petroleum based hydraulic fluid)
If there is any interest PM me.
Dave

 

[m1010plowboy]

Hi guys, I got an order in for newly manufactured air-pack Control Valve Piston Seals (the ones for the G749 M211/M135 not included in the M54/M809 rebuild kit)
They are essentially identical to :
Part Number 374272 for the hydraulic side of the piston, and
Part Number 375833 for the air side of the piston.

I will be offering these for $30 for the pair These are new, New Manufactured parts not New Old Stock.
The dies are being manufactured by a United States hydraulic seal manufacturer established 50 years ago and will be made on equipment in their facility.
The NRE on the dies was a bit pricey but only a single set of dies is required as the 2 seals are identical in size and shape the only difference between them is Shore Hardness (Durometer) and material (one is resistant to brake fluid, DOT3/DOT5 Silicone, the other is resistant to petroleum based hydraulic fluid)
If there is any interest PM me.
Dave

Have we told you lately how much we appreciate you around here? I'll let the northern fellas know. Thank you.

 

[Deuce2ndround]

Hi guys, I got an order in for newly manufactured air-pack Control Valve Piston Seals (the ones for the G749 M211/M135 not included in the M54/M809 rebuild kit)
They are essentially identical to :
Part Number 374272 for the hydraulic side of the piston, and
Part Number 375833 for the air side of the piston.

I will be offering these for $30 for the pair These are new, New Manufactured parts not New Old Stock.
The dies are being manufactured by a United States hydraulic seal manufacturer established 50 years ago and will be made on equipment in their facility.
The NRE on the dies was a bit pricey but only a single set of dies is required as the 2 seals are identical in size and shape the only difference between them is Shore Hardness (Durometer) and material (one is resistant to brake fluid, DOT3/DOT5 Silicone, the other is resistant to petroleum based hydraulic fluid)
If there is any interest PM me.
Dave

 

[Deuce2ndround]

Have we told you lately how much we appreciate you around here? I'll let the northern fellas know. Thank you.

Hi guys, I got an order in for newly manufactured air-pack Control Valve Piston Seals (the ones for the G749 M211/M135 not included in the M54/M809 rebuild kit)
They are essentially identical to :
Part Number 374272 for the hydraulic side of the piston, and
Part Number 375833 for the air side of the piston.

I will be offering these for $30 for the pair These are new, New Manufactured parts not New Old Stock.
The dies are being manufactured by a United States hydraulic seal manufacturer established 50 years ago and will be made on equipment in their facility.
The NRE on the dies was a bit pricey but only a single set of dies is required as the 2 seals are identical in size and shape the only difference between them is Shore Hardness (Durometer) and material (one is resistant to brake fluid, DOT3/DOT5 Silicone, the other is resistant to petroleum based hydraulic fluid)
If there is any interest PM me.
Dave

Hello Dave,

I realize this is an outdated response to the above information but we have two M135's here in Manitoba and we would like to get the brakes fixed up on them. Are these seals still available and if so, where can we get them? We've been searching for a long time and this is the most information we've been able to find so far.
We anxiously await your response.

Thank you!

 

[m1010plowboy]

Hello Dave,

I realize this is an outdated response to the above information but we have two M135's here in Manitoba and we would like to get the brakes fixed up on them. Are these seals still available and if so, where can we get them? We've been searching for a long time and this is the most information we've been able to find so far.
We anxiously await your response.

Thank you!

You're kinda new around here so welcome aboard. Sending Davyboysmith a Private Message PM is a great start. If you're navigating the site for the first time and can't find something, let us know.

The peanut gallery will be screaming for pictures and I am tracking vin/ serial numbers / unit markings / data-plate info / passenger side frame s/n stamp and drivers side horn CFR numbers if you're out snapping photos.

The most recent/modern info we could find comes out of Edmonton Brake and Clutch. https://edbrakeclutch.ca/

We spotted their corporate tag on a newish m207 air-pak. Heavy truck brake shops may still have parts or be able to machine/create/fudge what we need. Reaching out to Heavy Truck shops that are local might net the gold you need.



The online parts search for "G749 air-pak" or even "G749 air/hydraulic cylinder" can produce results depending on the day.

Have any of our G749 hunters ever bought parts off these guys?
https://www.defensetruckparts.com/contact

The kit on the bottom right looks exactly like the last G749 repair kit that we have seen in the distant past. https://www.defensetruckparts.com/brake-components

Repair kit, air pakPart no. 8333870 NSN 2530-00-318-0984

Watch out for online sales of wheel cylinders. There seems to be a weaker version of 1 1/4" wheel cylinders that were original on the American G749. We've heard stories about early leaks on new 'online' purchases. The Canadian wheel cylinders were/are/ in general..... 1 3/8".

I replaced a differential last year and was surprised to find plugged orifices at the brass 90's going into/ out of the diffs. Spending time cleaning and blowing the parts we have always helps.

What else do you need to get them stopping?

All we need to get them rolling is a hill.