M809-series (M818) Air Brake Retrofit

[Bandit02]

I suggest keeping your caging bolts in the cab, clean and ready to use if you need them. After awhile, the corrosion from aluminium & steel render them useless and crack the pot if left in their holder.

 

[MyothersanM1]

I suggest keeping your caging bolts in the cab, clean and ready to use if you need them. After awhile, the corrosion from aluminium & steel render them useless and crack the pot if left in their holder.

Thanks for the tip. Someone else had posted that same tip elsewhere on the site. I plan to throw them in my on-board tool box.

 

[MyothersanM1]

I have had photographic equipment issues, so I am lacking in new posts. I now have it fixed so I am back on track. Nonetheless, I have been busy progressing through this job.

I finished plumbing the air chambers on the rear axle. I installed 45º 3/8" elbows to route the hoses neatly inward and up over the axle. The left hoses sit a few inches safely behind the pinion shaft plate. I removed the cage bolts and installed a pair of brand new chamber plugs. I like the new look.


I fabbed up some simple air chamber hose brackets with loop clamps. They support and protect the hoses as they go up and over the differential housing. I made them with 3/16" X 1 1/2" strap steel, some 1/4" nuts, bolts and washers and some 3/4" loop clamps. The axle mounting holes were drilled 5 1/8" apart. This is the measurement between the bolt heads on the width of the pinion shaft cover atop the differential. I put a 45º in the rear bracket plate. When the rear axle articulates down, the hoses depart to the relays at a sharper angle as opposed to the amidships axles. The bend helps alleviate any strain.


Installation of the brackets was done by removing two 3/8" bolts from the pinion shaft cover plate and attaching the brackets with longer bolts and shim washers. I used the second row in from opposite ends of each axle. The original bolts were 3/4" long, I replaced them with grade 8 1 1/4" long. I stacked up some SAE washers for shims to keep the bracket plate at or above the pinion shaft cover plate.

VVV Rear VVV


VVV Amidships VVV

 

[MyothersanM1]

Moving on with more plumbing, I also removed the air pack and master cylinder. Now obsolete, they were in the way of progress. The MC bracket is useful in routing air tubing to the primary and secondary tanks and forward to the treadle valve fittings which will be on the firewall. I removed the brake pedal, but left the brake pedal lever in place. Two reason I left it: 1) it's not in the way and 2) it's more trouble than it's worth.


The primary and secondary tanks were connected to the 8.5 gal. supply tank which is mounted behind the cab. I used 1/2" tubing and fittings for the supply. Each tank is fed through a single check valve with a tee fitting. On the opposite side of each tee fitting is a 5/8" air brake tube fitting. 5/8" tubing from these two fittings will feed the treadle valve. The top tank is secondary and the bottom is primary. New pull type drain valves were installed on both tanks. The bottom drain was straight forward, but the top did not have enough clearance between the tanks. I used a 3 1/2" and 6" brass pipe nipple and a 90º elbow to route the top out and down. I am still in the process of how I want to route and dress up the pull cables.


The front and rear emergency glad hand connections route pretty much the same way as before the project. There is a bulkhead fitting just forward of the fuel filter that routes emergency air outside of the frame from the front gladhand. Inside the frame there is tee the feeds the horn, governor and dashboard. Attached to a 90º elbow, 3/8" tubing runs under the cab, crosses under the utility box/spare tire rack to the right frame rail and feeds the transmission poppet valve and on back to the rear glad hand. I installed a bulkhead fitting where the trailer air valve used to be on the rack. I attached a 3/8" air brake tee to the bulkhead fitting then routed the air up to the supply tank with 1/2" tubing and fittings. I replaced the length of tubing from the tee under the rack all the way back to the left frame bulkhead fitting. I would have had to splice it otherwise and I don't like doing that.

 

[MyothersanM1]

The service brake (5/8") and spring brake (1/2" red) supply lines were connected up to the primary and secondary tanks. A double check valve is installed between the secondary tank and both supply lines. The 3/8" parking brake valve supply line is also connected here with a 3/8" air brake push-to-connect fitting teed from the spring brake line. The plumbing routing I used is from a Bendix schematic. I posted it earlier in this thread.


The parking brake supply line loops up to the diagonal part of the cab floor board. I installed a bulkhead fitting to the left of and below the high beam switch.


The delivery line for the parking brake valve connection runs along the driver's door with my custom air horn tubing. I reused the bulkhead fitting that carried brake fluid from the now out of service master cylinder remote reservoir to route the air line down and out of the cab. I was short the correct fittings to complete . I have since ordered them and am waiting for time to install.


The parking brake valve was installed in the knock-out just below and left of the starter switch. The hole had to be reamed to 7/8" using a step bit. The fit is a little tight but it will work.


The blue tubing connected to spring brake valve is the delivery line from the parking brake valve. The only line left to connect here is the control line from the treadle valve. I have yet to install the treadle valve.


Tucked behind all the tubing is a double check valve. The rear axle service line from the treadle valve will connect here. The front service gladhand line will connect here also on the opposite side of the valve. The check valve will allow for air to route from either the treadle valve or from a towing vehicle, but not both. The lines going to the rear axles and the rear service gladhand in addition to the stop light switch can be seen connected to the two brass tees.

 

[MyothersanM1]

I'm back. I got a few things done this past week. To continue my last post, I removed the parking brake valve to photograph the plumbing detail.


With the parking brake brake valve installed, I turned my attention to getting all the rest of the cab appliances installed and plumbed. The treadle valve and foot pedal came in the kit pre-assembled and included a firewall reinforcing mounting plate. I painted the mounting plate with coat of Rustoleum flat black as it was bare steel delivered. All the mounting holes and pass through holes are pre-drilled.

The lower curved portion of the plate fits up against the steering column firewall bracket. The top of the plate has diagonal cuts on either side. These cuts allow the plate to mount up between the captive nuts that hold the lower side of the power control box and turn signal flasher bracket in the engine compartment. Due to this high mounting and interference of the PCB/flasher bracket, only the two lower (No.1 primary/rear brakes) pass through holes can be used to attach fittings to route air lines. The top two pass through holes will just accommodate two hex-socket pipe plugs. The (No. 2 secondary/front) connections will be made in the cab using bulkhead fittings to route into the engine compartment, short runs of tubing and the connection ports found on the sides of the treadle valve.


I dry fit the mounting plate plate to the firewall marking the two lowest 3/8" holes for drilling. I removed the plate and and drilled the holes. With assistance, I mounted the plate at its bottom with 3/8" X 1" grade bolts and lock nuts. I drilled the three treadle valve 3/8" mounting holes directly through the plate. The pass-through holes were cut with a 1 1/8" hole saw with the pilot bit removed using the large pass through holes in the plate to guide the hole saw. Inserting a couple 1/2" pipe nipples to help center the treadle valve and an extra hand, the valve was mounted with 3/8" X 1 1/4" grade 8 bolts through the firewall and mounting plate. Studs would have been easier, but bolts were readily available.


As I had mentioned before, I am not removing the old brake pedal lever under the floor board. However, I have plated the exiting hole in the floor board where the pedal shaft passed through. I got a 3" electrical junction box cover from the hardware store, painted it sand and attached with a couple self-tapping sheet metal screws.

 

[MyothersanM1]

I have pre-assembled the front LQ-4 proportioning valve. The whole assembly will mount to the crossmember under the transmission and I have made a custom bracket for this purpose. This valve will also be fed through a double check valve as are the rear brake valves. This check valve will allow for the front gladhand to be used in flat towing isolating the on board treadle valve. The tee fitting will feed actuating air out to the front wheels.


I cut a hole on either side of the frame and installed a 3/8" bulkhead fitting where the front brake chamber air lines will pass through out to the wheels.


I am hoping in the next week to finish up the plumbing and valves installation. I want to get started on getting the front axle up to speed with this project and get it all put to bed.

 

[MyothersanM1]

I finished up all the in-cab plumbing to include a new air pressure gauge and added two low air pressure switches to the existing system.

I added two low air pressure switches for both primary and secondary tanks. I used the M35 type (p/n 11621847) switches that open at 60 psi. A 1/4" brass tee was plumbed into each of the supply ports on the right side of the treadle valve. There is constant pressure at these ports directly from the tanks when the system is fully charged. I used two five wire instrument cluster harnesses (p/n 8376502) two connect the two new switches in parallel to the existing low air warning buzzer and light. One harness was connected to the "line" side and the other to the "load" side. I had to change the packard connectors to male on the buzzer connection and the existing switch power connection to be able to connect to the 5-wires. I ended up plumbing the switches on the perpendicular outlets of the fittings as they fit better under the dash board in that configuration.

At the end of the brass tees, I plumbed in two 1/4" push-to-connect X 1/4" NPT fittings to feed a dual air guage for the primary and secondary tanks.

I found this nice dual air gauge by GBI Precision (p/n 115162) searching the internet. The aluminum bezel is an eBay find from a seller who specializes in "tuner car" customization. I bent it from 90º to 135º to facilitate easy reading from the driver's seat. It mounted up fairly easy right next to the heater controls. The gauge is connected to the air system using two 1/8" NPT female-female fittings, two 1/4" push-to-connect X 1/8" NPT fittings and 1/4" nylon air brake tubing. I sat in the driver's seat and the gauge is nicely visible and doesn't interfere with my right leg. I still need to adapt the backlight to plug into the instrument cluster lighting.


I was not able to test the new system. I still have to install my new air dryer and connect up the whole discharge system to the supply tank.

 

[PWM]

Great work, almost time to install an air ride seat.

 

[MyothersanM1]

Great work, almost time to install an air ride seat.

I did convert the standard springer base to air ride by removing the spring and replacing it with an air bag some time ago. The seat was replaced with a HMMWV type. It works really well.

 

[SLOrazorsedge]

You certainly demonstrate more than just backyard wrenching experience. Very nice work brother! So this mod will not work for a M939 with 14R20 singles as the hubs are flipped? I took my M936A1 wrecker out for a run yesterday pulling a few hills. On return as I normally do, I shot my IR gun on all the hot spots, radiator, front hubs, diff, rear hubs, transmission, etc. My rear brake drums (all 4) were running 330F +/-. I think S cams would definitely run cooler?

 

[MyothersanM1]

You certainly demonstrate more than just backyard wrenching experience. Very nice work brother! So this mod will not work for a M939 with 14R20 singles as the hubs are flipped?

Thanks for your support. It's been a lot of work, but will all be worth it.

This set-up requires the hubs to be in their normal position. The furnished brake drums attach inboard from their backside to the hubs via the studs through the flange. With the hubs flipped there is nothing for the drum to attach to. I am sure an adapter could be fashioned barring all clearances.

 

[MyothersanM1]

Here are more pictures of plumbing completion. I got tired and left the storage yard without photographing these details.

This a detail of the treadle valve primary connections that go directly into the back of valve. It consists of a 5/8" air brake X 1/2" NPT, a 1/2" NPT female-female connection fitting and 1/2" NPT X 1" L nipple to supply air pressure from the primary tank. The service line to the rear R-12 valve is connected with a 3/8" air brake X 1/2" NPT fitting and a 1/2" NPT male to female adapter. I used the extra fittings to get some stand off from the firewall.


As mentioned before, I could not use the secondary supply and delivery ports on the back face of the treadle valve due to the control box/flasher bracket on the fire wall occupying that space. I cut to 1 1/8" holes in the firewall just below the treadle valve and above the "crease" in the floor board then installed two 1/2" NPT bulkhead fittings and a 1/2" push-to-connect X 1/2" NPT fitting in each one.

On the treadle valve, the left-side secondary supply port (1/4" NPT) is connected the left bulkhead fitting using a 1/2" push-to-connect X 1/2" NPT fitting with a 1/2" NPT to 1/4" NPT reducer. The right side secondary delivery port (3/8" NPT) is connected to the right bulkhead fitting through a 1/2" push-to-connect X 3/8" NPT fitting. Both sides are connected using 1/2" nylon tubing. Sorry for the lack of clarity. It's difficult to get good pics under the dashbord at that angle. I had the brake pedal out to tweak some of the bends to center the pedal up between the clutch and accelerator pedal.


On the engine compartment side, I used air brake compression fittings. The supply (right side fitting in pics) from the secondary tank is 5/8" air brake x 1/2" NPT. The delivery to the front axle proportioning valve is connected to a 1/2" NPT tee through a 1/2" air brake X 1/2" NPT fitting. The 3/8" air brake X 1/2" NPT fitting at the end of the tee feed the control port on the SR-1 spring brake valve.


The LQ-4 proportioning valve was mounted up to the cross member under the transmission toward the right side of the truck.


The 1/2" air brake connection in the left of the pic is the delivery line from the treadle valve. The 3/8" air brake tee at the bottom center feeds the bulkhead fittings installed on either side of the forward frame for the front brake chambers. The 3/8" air brake line to the upper right and leading off to the left is the supply from the front service glad hand. Both front and rear brakes are tied into the front service gladhand for external actuation when needed.


A wider angle shot of how everything fits and is dressed up.

 

[MyothersanM1]

This past Sunday I made a temporary discharge connection from the air compressor to the supply tank. I started to air things up and found two air leaks.

-There is a small 1/8" NPT port at the top of the treadle valve against the fire wall. I did not plug that and it was gushing air. I disconnected the rear/primary supply and service lines, removed the fittings and unbolted the treadle valve from the firewall. I installed a recessed pipe plug (which I had the foresight to have a bag of them on hand) and problem solved. I took the advantage of the situation and reinstalled the treadle valve with 3/8" studs. The valve is MUCH easier to install with the studs. I reinstalled everything and moved on.


-The emergency line that runs the length of the truck crosses from the left frame to right under the the spare tire rack. There is a tee in the middle of the rack with a bulkhead fitting where the old trailer emergency line used to be. The supply tank feeds both front and rear gladhands and all other air serviced accessories at this point. Well, I forgot to snug down one of the fittings leading from the supply tank down to the tee. At almost 120psi it let go...HELLO!. I reattached everything and this time snugged it down.

With everything tightened up, I aired up the truck. I plugged the front axle air lines as they are yet to be installed. I released the spring brakes and set them making sure they were in the proper position respective to the valve setting. All good!
Releasing the spring brake, I made six service brake applications to properly set the automatic slack adjusters. All good!
I moved the truck back forth a couple times and, MAN, these brakes are NICE! What I like most about air brakes is the light pedal pressure required to actuate them.
Anyway. party over. I still got more to do.

I installed the Haldex air dryer on the frame crossmember just forward of the amidships axle using the Haldex specific bracket (DQ6051). I have the AN fittings I need. I am just waiting for the braided steel teflon discharge hose to come in the mail to properly plumb the discharge line. I also have to connect up the control tubing and the delivery line to the supply tank.


I shortened up, crimped down some new pull loops and dressed up the primary and secondary tank drain valves pull cables.


The front axle has been torn down awaiting new inner seals, knuckle boots and all the new brake appliances. The parts are all on hand and I am just waiting for the time to get it all done. And, I remembered today to get a pic of the new budd caps and lug nuts for all the rear duals.

 

[MyothersanM1]

Here some quick updates. Not directly pertaining to air brakes, but part of the whole sequence, I replaced both front inner axle seals with new retainers and finished installing new knuckle boots. I put the boots on last night after work and allowed the RTV to set up over night that I put on the zipper and the retaining clamp nut and bolt.
I cleaned up the knuckle brush guards and gave them a coat of Rustoleum flat black. Flat black hides the grime better than tan.
I have also finished degreasing and cleaning the front axle CV joints and cleaning up the spindles.
I am going to take a wire wheel to knuckles and clean the old sealant off between the studs.
Looks like everything is ready to go back together. What am I missing???.........Oh, yeah! TIME!


Now a note about the front axle spindle/spider mounting studs. The M939-series front wedge brake spiders do not have mounting whole adjacent to the actuating cylinder side. So, I removed the "one o'clock" stud on the left side and the "eleven o'clock" stud on the right.

 

[MyothersanM1]

This morning I greased and installed the front axle shafts. I installed the spindles with a bead of ultra black gasket maker, the brake spiders and bolted it all down. Don't forget the the deflector ring over the spiders before the nuts go on.... I indexed the air chambers with ports facing up and tightened down the collet nuts. The newly painted knuckle brush guards were also bolted back up.


This afternoon I had enlisted the assistance of my father-in-law to put on the hubs/drums. First, we put on the brand new brake shoes and return springs on the spider. I applied a small amount of the clay-base grease called for by Meritor on the anchor points, adjuster points and around the retaining clips.
I installed the inner bearings and seals on both hubs to prep them for installation. I coated the insides of the hubs generously with grease, but not packed. I also put a light coat on the spindles.


Using a floor jack, we lifted each hub/drum into place on their respective spindles and slid them home. The right side gave us some problems. With the first attempt, the bearing jammed on the spindle toward the inner side. I pulled the hub/drum off and the bearing and seal stayed on the spindle. I coaxed the bearing off and reinstalled it the hub. Second attempt was the charm. Left side went on without an issue. With a coat of grease on the bearing races, the outer bearings went in, the inner spindle nut was installed and hand tightened using the spindle nut socket. I trash-bagged up both ends and will finish up on another day.


To finish up the plumbing work to the air dryer, I ordered some 1/2" braided steel teflon hosed, two 10AN 90º swivel fittings and two 10AN to 1/2" NPT adapters for the discharge line. I installed one fitting, but I need to dry fit the line to get an accurate length cut.
I also picked up some more 1/4" nylon air brake line and some push-to-connect fittings to install the control connection.

 

[Swamp Donkey]

You mind sharing the brand of clay based grease you used. When I do my front seals I'll be lubing the brakes too. Do you use this same grease on the wedges?

While the TMs do a good job of explaining disassembly and maintanence of the brakes, they can't compare to a thread like this. I've really come to appreciate this thread since it'll be my first time going into the fronts. Great job!

 

[MyothersanM1]

You mind sharing the brand of clay based grease you used. When I do my front seals I'll be lubing the brakes too. Do you use this same grease on the wedges?

While the TMs do a good job of explaining disassembly and maintanence of the brakes, they can't compare to a thread like this. I've really come to appreciate this thread since it'll be my first time going into the fronts. Great job!

I do not know the brand of grease off hand, but I ordered it from McMaster-Carr. I can get the brand name later today after work. Here's a link if you want to order some...
http://www.mcmaster.com/#1295k63/=y8h8cd
All the internal parts, wedges, plungers, ratchet pawls, etc., to include the outer points that contact the moving surfaces of the brake shoes, on the spiders were lubricated with this grease.

Here is a Meritor tech manual .pdf that really gets more in depth into explaining these brake set-ups.
http://www.axletech.com/resources/service_manuals/pdf/MM_4R.pdf

 

[MyothersanM1]

Here is the label on the clay-based grease.

 

[MyothersanM1]

Almost forgot to add, I installed, properly torqued (preloading the bearings) the spindle nuts and washers. I concluded with bolting on the front axle caps with new gaskets all this afternoon after work.