FMTV Brake Chamber Replacement

[NDT]

Figured I would cover this since the -20 does not go into detail. My chamber would leak air when the parking brake was released. To remove the chamber, on the rear axle, I had to of course disconnect the three air hoses, and additionally, remove the brass adapter fittings, so the chamber could be threaded out. Next, cage the spring brake. Next, using a drift punch, loosen the lock nut on the chamber threaded shaft. At that point, you should be able to unscrew the chamber. You will need to cage the new chamber before threading it in. Make sure to use antiseize on the threads during reassembly. Thanks to Keith at MTP Drivetrain for fixing me up with the new chamber.

 

[mkcoen]

Thanks for the write up on this. I'll be doing that tomorrow.

A handy item to have in your vehicle tool box is a 3/8" plug to block off the air supply line in case you're in the middle of no where (or sitting in line for a parade) and the diaphragm decides to crap out on you. You can pull the supply hose, plug it, and drive on. Hopefully this bit of info will save someone else issues while sitting along side the road.

 

[mkcoen]

Has anyone else done this? I'm having a heck of a time getting the lock ring loose. Tried NDTs drift suggestion with no luck - kept slipping off every time I tried to hit it. I then tried a chisel to get a better bite but I can not get the thing to budge one bit. It's been soaking in WD40 since yesterday and still not able to get any movement.

I was hoping to source one locally but no luck. At this point, since the trailer is just sitting in the drive I'm thinking about pulling one off of it to get the truck back up. Of course I need to be able to get the stinking thing off first.

 

[coachgeo]

...It's been soaking in WD40 since yesterday and still not able to get any movement....

Water Displacement formula #40 (WD40) is not really a very good product for this type project. You need a "penetrant" like PB Blaster, Liquid Wrench etc. You can soak in WD40 for a week and it won't do you much good compared to using a "penetrant" for an hour or two.

You'll get it figured out. You always do.

 

[Smike740]

I had the same problem on my 5 ton, I couldn't get the lock nut loose and there wasn't enough room to get a pipe wrench on the lock nut. I have removed 2 by using a large pipe wrench to loosen the housing by putting the wrench on the pipe section of the housing near the lock nut.

 

[f8617]

I tried to remove one, using all previous stated techniques, without success...thankfully solved problem of NO parking brake and slight chamber air leaks with liberal doses of WD40.
Perhaps, heat from a "blue-tipped wrench" (torch) may be necessary, should air chambers need replacing in the future.

 

[mkcoen]

Keith_J came by this afternoon and we finally got things switched out. The trick seemed to be, for mine any way, to remove the wheel and brake drum to be able to get a good angle on whacking the ring with a drift. Keith had a nice 1" square drift compared to my tapered one so put more meat on the ring when hit. Still it took considerable encouraging to get it off. The chamber came off fairly easily after heating it up a bit. We checked for leaks in the driveway but it was getting too late for a road test so I'll be doing that tomorrow.

 

[f8617]

How do you dispose of an old air brake chamber?
Would shooting it from 200yds with a 308 be a safe option?

 

[m pilot]

use a acetylene torch to cut a hole in the spring brake side and then cut spring to relieve tension

 

[StrykerPerry]

What part number did you use to order it

 

[JD4044M]

On Big Round things I use a Chain Wrench better than a pipe wrench sometimes due to a large diameter.