Air Pak Rebuild

[Gunfreak25]

By the way, as soon as I get a darn replacement cable for my camera I would like to make a tutorial on how to disassemble, service and reassemble parts specific to the G749. Things like the Air Pak, bearings and seal replacement, wiper motors, even the air compressor when mine eventually bites the dust and I have to get a new one. This is an effort on my behalf to try and get some informative sticky's put at the top of this section of the forum which, like the Korean war seems so forgotten to me. We GMC owners have to stick together.

 

[CAPSARME]

i found Air COMPRESSOR kits, but no airpack kits......

 

[Gunfreak25]

What may I ask do the air compressor kits contain?

 

[M215]

The Bendix air paks used on the 5 tons (M809 / M54 series) are a larger version of the one used on the M211 / M135. As stated earlier the 5 ton rebuild kits are 95% usable for the GMC, only one seal missing. I have rebuilt several GMC air paks with 5 ton kits, very easy to do. Never paid more than $25 for a NOS kit through Ebay.
Karl

 

[Gunfreak25]

Would you recommend I rebuild my AIR PAK? It has not been used for over 30 years and I don't know if it works or not yet as I have not gotten that far. The only line that's been disconnected from the AIR PAK itself has been the air inlet port and the VENT port. It's never been removed from the truck so most of the mounting bolts and hydraulic line fittings are frozen up pretty good. It would be a real chore to remove!

 

[M215]

Tom,
I would rebuild the entire brake system, not just the air pak before hitting the road. You have 12 wheel cylinders, lots of hard and rubber brake lines, master cylinder that all need attention. Since these trucks have a single circuit brake system, you loose one line and you have no brakes. Eveything is avaliable for your truck, so no problem on parts. Watch out for NOS air paks, I have 5-6 that I have as spares. After sitting for 40 + years on shelves I wouldn't even trust these.
Karl

 

[Gunfreak25]

Thanks, Karl. I will add the AIR PAK to my list. Hopefully that one elusive little seal is good and a 5 ton kit will take care of everything. Luckily for me the previous owner has already rebuilt the master cylinder and 10 wheel cylinders. 2 of them were FUBAR so I'll be needing 2 new ones.

I was just going to replace all the flex rubber lines and the steel lines on the axles. But I will go ahead and replace ALL of the steel lines as per your recommendation. Actually NAPA has everything I need here and it will cost well less than $100 to replace all of them on the truck.

In which case when it comes time to drop the air pack I'll just cut the old hydraulic lines off of it instead of wrestling with the rusted fittings for a week. I can't fit under there very easy........

 

[nattieleather]

It takes some time, but once you go through the brake system and rework everything you will stop and stop good! You may find that your air pack just needs cleaning like mine did. It was my wheel cylinders, master cylinder and the wheel adjusters that needed attention on my truck. Fixed all that and boy would it stop. I like to say it'll stop on a dime and give you 8 cents change... Get that cammera part and show us how it's done...

 

[USMC 00-08]

Thanks, Karl. I will add the AIR PAK to my list. Hopefully that one elusive little seal is good and a 5 ton kit will take care of everything. Luckily for me the previous owner has already rebuilt the master cylinder and 10 wheel cylinders. 2 of them were FUBAR so I'll be needing 2 new ones.

I was just going to replace all the flex rubber lines and the steel lines on the axles. But I will go ahead and replace ALL of the steel lines as per your recommendation. Actually NAPA has everything I need here and it will cost well less than $100 to replace all of them on the truck.

In which case when it comes time to drop the air pack I'll just cut the old hydraulic lines off of it instead of wrestling with the rusted fittings for a week. I can't fit under there very easy........

Are these parts specific to the truck or something that you are going to make work for it? When you get time, would you post part numbers for what you get?

 

[Gunfreak25]

When I can get some tutorials going I'll be sure to list where to find said parts and any part numbers I can. Normally I just stick with NOS parts or if they are simple seals, make my own. As for the window wiper motors, it appears they use leather "cups" and as such they cannot be easily replaced. No reason to really, if they aren't really worn. In which case I'd just get a new unit. I'd also like to cover G749 weather stripping too. NOS stripping is simply not available anymore so I have an idea for getting things water tight again.

 

[Atomic]

We GMC owners have to stick together.

Roger, roger.

I took my airpack off about a month ago along with most of the lines for replacement. I'm glad I found this thread. I had read a while ago that kits weren't available and so I had jsut resigned myself to getting a "used c1" one. Great stuff on the 5 ton kits. Thanks!

 

[Gunfreak25]

Like I said, when I pull mine apart i'll be seeing what I can find that replaces that one elusive little seal that the 5 ton kits do not contain.

 

[tburk49760]

Bump. Any new info on this. My XM215 needs some loving in the braking arena. I'm having a hard time finding a source for the 5 ton airpack repair kits and I'm also a bit concerned about that one or two pieces that don't fit from that kit.