GMC Air pak database

[Gunfreak25]

This is the 2nd time typing this out since I accidentally deleted it. So bear with the lack of enthusiasm in information listed below.

The M211 and M220 trucks use a Bendix AIR PAK model # 2500685
It is unknown if this is the same model used on M135's.

For those who are installing 5 ton rebuild kits in their AIR PAK's we all know by now the only thing the 5 ton kit does not replace are the 2 small control valve piston seal's.

These two control valve piston seals are not the same. They are both installed with the V sealing lips opposite of each other. One seal is for the hydraulic side of the piston and is part number 374272. The other seal is for the air side of the piston and is part number 375833. The difference is the hydraulic seal is made of harder material. These can both be ordered from Brake Systems Inc in oregon.

More research has yielded a page listing ALL the AIR PAK models manufactured by Bendix through the years. It lists the length differences between the models to help you identify exactly which model your truck has.

As I said the M211 and M220 use Bendix 2500685. It appears that Bendix 2500690 is a suitable replacement, just swap the brass fittings over since they are smaller on the model 690.

The Bendix Model 2500690 can be bought from NAPA for $400.
NAPA AUTO PARTS

HERE IS THE LINK TO THE AIR PAK PDF FILE. GO TO PAGE 80 FOR THE INFO.

http://www.precisionrebuilders.com/pdf_catalogs/VacCatalogPHB-0398.pdf


This information came at a good time as it appears Alfa Heaven is now out of AIR PAK's for the GMC's. This is likely indefinitely. Long live GMC's. We'll keep them going one way or another.

 

[hendersond]

Thanks again Tom.

What is the approximate cost of the rebuild kit?
Where can it be purchased most cost effectively?

 

[Gunfreak25]

Rebuild Kit For The M54/M809 5 Ton Truck Air Pack, 8333870

You will need this kit and 2 of the control valve piston seals mentioned above, from Brake Systems Inc in Oregon.

 

[135gmc]

The AIR PAC is the same for the M135.

 

[Stan Leschert]

Quick question .... Who was looking for a gas tank? I found an NOS one, and the guy is downsizing to M37 only.

I'm not profiting, just helping a buddy clean up his stuff.

PM me.

No, he is not downsizing any M37 parts.

 

[Gunfreak25]

Mine's got a big ol dent in it.

 

[JGBallew]

Holy Christmas, wish I'd known this earlier.
Had a friend go through a bit of nonsense dealing with a builder who basically rattlecanned his airpack, and charged him around $200 dollars for the pleasure.

Filing this away in the " YOU WILL NEED THIS INFO " folder.

 

[hendersond]

I just called today, $123 for the M211/135 rebuild kit. I will order it Monday.
Its just good to have one around

 

[Gunfreak25]

Where did you find an M211 air pak kit? Everywhere I have looked has been out of them. I need one too!! That is cheaper than the 5 ton kits as a matter of fact.

 

[hendersond]

I calles BSI in Oregon just like you told me and said I need a rebuild kit for a Bendix 2500685. The said they could make a kit, called back in 2 hours with the price.

Right??????

 

[Gunfreak25]

That would be a negative buddy, BSI told me the kit they piece together for the 2500685 AIR PAK only contains soft parts. So no check valve or the big shiny control valve assembly which has a non replaceable permanant seals staked in place.

I suppose depending on the condition of your AIR PAK the BSI kit would work. But mine, like most others here needs the more complete kit the 5 ton surplus one provides.

 

[hendersond]

Tom, I was going to order it and then I thought maybe I should hold off and run it past you. Glad I did. Nothing is ever easy. Thanks for the heads up!

I'll call them again monday. Maybe I better go look at my parts truck.

 

[Gunfreak25]

I am working with another parts house and parts guy who has been playing with AIR PAK's for 30 years. This guy is an old timer, super friendly and knows his beans. He said he can piece together a GMC rebuild kit for under $100. It will not include a new poppet valve unit. This is the piece on the front of the AIR PAK with permanantly crimped seals and 6 bolt holes. Instead, you send it to him and he installs new seals. He had to make his own tools to do this.

He also has replacement parts for all the different AIR PAK's. I am ordering a replacement control valve bore and slave cylinder bore from him since mine were pitted.

The man is so committed to his job he keeps a wall of fame of people/trucks he has helped with repairing the brakes on.

 

[yamaha]

Hello all. BSI does not have the seals mentioned earlier in this thread. I believe they are knowledgable people but are reluctant to tell others what seals work in there place. Also, they have no "hard parts" such as springs, clips, etc. If you send him your core, they will try to rebuild using used parts from other peoples cores. for the money, its worht it if it works. But they also sell a new "drop-in replacment". however will not disclose the model number on this either.
We are all here for the same reason. We wants to keep our history on the road safley for our childrens and everyones concern. BSI is the second shop i have found that rebuilds these but will not share the infromation for the public to keep thiese on the road. The other shop has the correct replacement parts numbers for the seals , but again, will not sell me just he seals. i have to give him $450 for the rebuild or or $78 per seal. This is an abomination and insult again us at U.S. citizens. If i find the seal numbers i will share with all who seek them. Thanks everyone. God Bless.

 

[Gunfreak25]

BSI does have the seals, I had a 45 minute conversation with their shop foreman, Nathan. Older man, been there a long, long time. Even talked through email later on. He was more then helpful in getting me part numbers and how to information. Their "up front" folks at the desks pushing the pencils and paper around may not be so helpful for liability reasons. We are after all, dealing with antique brake parts!

 

[yamaha]

are you sure? i have been talking with a guy in the shop the last few weeks. he said they have the 374272 but not the 375833. He stated this was a harder material and they cannot get this seal. He said they jsut clean the unit up and replace what tey can. if it works , then it passes. I believe the guy was Jesse at BSI that i have been dealing with. He stated he can no longer get this seal. Without it, the other is useless was my understanding.

 

[yamaha]

also , It would be nice to knwo what air pack they are replacing it with. the latest 2500690 has been sold out for years. They have one they bolts right up. the only bracket that does not fit is the rear bracket because the can is a little larger. i have an m211,m135, and the dump truck version i believe is an m217? they all need air packs. have no brakes in any of them.

 

[Gunfreak25]

MY BAD. Precision Rebuilders is who you want to talk to. Speak with Nathan, he will fix you up right quick. It's been too many months since I have been down this road of GMC restoration and I cannot remember any of the part or model numbers for the different air pak's. Talk to Nathan and have a pen handy!

 

[yamaha]

Thanks Gunfreak25! Are they in missouri? if so i think i foun the right phone number. Does he have the seals? Also does he sell a complete air pack? thanks again!!!

 

[SturmTyger380]

From the previous post - 'As I said the M211 and M220 use Bendix 2500685. It appears that Bendix 2500690 is a suitable replacement, just swap the brass fittings over since they are smaller on the model 690.

The Bendix Model 2500690 can be bought from NAPA.'

Has anyone used the 2500690 on their truck?

I am good at working on stuff but if it will swap in it might save time.

Alan