Geoff Weeks

Yes, the tie-rod just keeps the tires in "sync" with eachother and the forces are supplied by the dual boxes. Sheppard made a "box" that looks identical to the "392" but it has no input shaft, the oil is controlled and supplied by the master box (Left in the US). Some others have used a double acting hyd cylinder, much cheaper, but when pressure is on the rod side of the cyl the forces will not be equal like they are with the whole slave gear. (Rod side has less area than the non-rod side).

Glad I could be of help.

Make sure the line between the double check and trolley valve is not "crimped" anywhere along its run.

Yeap, that is the double check, the outlet is the pipe connection that looks like it connects to a tractor protection valve. The reason it fixed it is because without all the air line connected the flow out the exhaust was higher and that was enough to get the shuttle to move. It sound like it was "sticky". It may work for a long time or it may fail shortly, but at least you know where it is and how to fix it. Doesn't look like fun getting it out of there, however.

Output from the trolley. It goes to a T valve where the higher of the two inputs goes to the output (double check). Right now it is not sealing so air can come from the foot brake, back feed up the line to the trolley and since in its normal position that is open to exhaust, the air flows out the exhaust. Another way to test it is to build full air pressure, fully apply the trolley, then step of the foot pedal. It shouldn't leak until you release the trolley valve. Input to the trolley should have system air, output should be 0 psi with the valve in the normal position, and of course the line you already traced just dumps to under the hood. With the air built up, if the line you crack loose at the trolley has pressure, that is not the one you want, if you crack it loose and it doesn't have pressure, then remove it and plug it, then test the foot brake to confirm the problem has gone away. then trace that line to a valve with three lines on it.

There should be 3 lines to the Trolley, (2 on earlier systems where they just exhausted the air into the cab) One should be supply pressure and one should be output that will go to the double check. 3rd is the exhaust you traced. Where it would be located is up to the mfg and I have no idea on that model, where they put it. It could be located anywhere between the trolley, foot valve, and the tractor protection valve. Some are in the cab, some are down on the frame. If you are in a pinch and need to move the truck, remove and plug the output line from the trolley valve (plug the line, not the port on the trolley valve) and the leak should go away if the shuttle (double) check is the problem. You should still put the time in to fix it right.

My 1st guess would be the shuttle check that separates the Johnny Bar from the foot brake feed to the tractor protection/trailer feed.

Ok, we were both writing at the same time, but that is helpful. That should rule out the Tractor protection valve, as it should see application pressure when either the foot or hand valve is used.

wow, I stopped working on trucks commercially in the very early 2000's and it was very rare to see a truck without a 'Johnny bar" even if it was a straight truck (dump truck etc). So, because there are two complete systems that are supposed to be isolated from each other, to prevent a failure on one system from effecting the other, you should start looking where the two come together to feed the trailer brakes. This would include the double check for the tractor protection valve, the double check for the Johnny bar if equipped, and the tractor protection valve it self if it is one of the newer type that has the double check inside the tractor protection itself, unlike the old TP-3 Note, the tractor protection valve is NOT the red and yellow buttons, that some call the tractor protection valve.

Does it leak when the "Johnny bar" (Trolley valve) is applied?

Trace the "Little yellow line"back to what it is connected to. You know where the air is exiting the system, so work back up until you find the problem. Does it drain both primary and secondary tanks? That would be a clue it is a problem in the trailer portion (trailer brakes can be fed by either primary or secondary so a failure in one does stop the trailer from braking). There are portions of that system that are "live" even if no trailer is attached or the "red button" is pushed.

The stamped steel mounts inside the drum, and is held in place by the same bolts that hold the drum to the hub. It seams to be left off newer set-ups, My guess the improvement in seal tech made them obsolete.

Gunite's offerings https://www.accuridecorp.com/sites/default/files/resources/2023-08/WE1.011 Rev. 4 Gunite Brake Drum Product Catalog 8-7-23.pdf

here is Webb's offerings, you can look up by brake diameter, you need inboard with 6 or 5/6 mounting holes, and with the pilot measured from your old drum. https://www.webbwheel.com/webbipad/pdf_files/SD 090 - 2019 Catalog.pdf

15x5 sounds small for a B85? IIRC that size may be used by wedge brakes. I have some that have a stamped steel piece that is like your concave bowl. I don't have a lot of Mack axle experience. I would 1st try and get some numbers 2nd I would grab a catalog and start looking for drums that match those measurements.

1st measure the ID of the drum, along with how wide the shoes are Next measure the pilot diameter (red) and the bolt circle diameter (blue) and start looking for a match Ideally you'll have a Mack # or a casting # to try and cross.

Lets start with the basics: What are the high and low side pressures with the system running? What is the air temp just in front of the condenser? What is the temp coming out the center vent? There is a lot more to it, but at least this will be a start. A clogged cabin air filter can cause low air flow, and reduced cooling.

whoo-boy, that is going to be difficult is my guess. Look for some casting numbers on the old drum. If one got that hot, it is likely you'll need two. Once a drum get hot, it gets hard and will not grab the lining, requiring more pressure to stop, which leads to what you see in that picture. What is the brake size? Hopefully it is a common size.

Yeah, there are a bunch a laws/truck configurations that only apply in one or a few states that aren't legal nationwide. When I hauled under MI rules, I was moving a crane that I would normally move on 5-6 axles and an overweight permit, but at the time Michigan's "Frost law" was in effect and they wouldn't issue any over-weight permits, I think I was 9 axle and well over 100' long but "legal" weight for a Mi train. I could get a over length permit. I don't remember what the GVW was when I made the move, but all the steel sure added to the weight to put all those axles under the load. Funny part was: when I got to the refinery where the crane was going, I wanted to drop the jeep and stinger and just move on 5 axles. The guy leading me in, said he didn't want to wait for that (it was near quitting time) and anyway they had no problem getting OD loads where this was going! After snaking though the refinery roads in and around piping and tanks, he pointed to an opening in the racking and said "back it in there'! Yeah, how many of you can back 3 sets of joints though a narrow opening in pipe racking? I got it done, but it would have been much quicker on 5 axles and one joint!

Paul, the "Michigan Train" is a weird set up, axles are a duel tire axle and are 'fixed" but limited to 13K last I knew. GVW limited to 160k. None of the axles are a single wheel nor steerable. The idea is to reduce ground pressure by spreading over many axles. I forget the man who came up with it, but the theory is more axles at a lower weight is easier on the road than traditional semi with axle weights at 17k-20K. There are a bunch of rules you have to meet, I can't remember them all, it has been 30 years since I pulled under those rules, and only did one load. IIRC steer and drive wheel can carry more, but trailer and any jeep/stinger had to be at 13k. They do "grone and pop" when they turn. The theory may work going straight but turning it is hard on roads and equipment. It is only legal in MI and some small parts of Ohio and Indiana, between the steel mills and the boarder with MI.

IHC had them under the passenger seat, meaning the seat had to be pulled out of the truck to access😕

Unless you painted that mark on with the engine and compressor engaged, I don't know how you expect them to be lined up? Belt will start turning before the compressor clutch will be energized, same when you shut the engine off, clutch will release before the engine stops turning.

Again, without pressures and temperature, everything is a guess. Pressure readings will tell if the compressor is compressing or not. A/C work can get expensive if you "learn as you go".

How do you know you have 3 lbs in there, did you put it in by weight? how doyou know it STILL has 3 lbs in there when itwill not hold a vacuum?

IF the compressor is running and you suspect a refrigerant side of the system to be at fault, you MUST provide pressures and temperature reading for anyone to do more than guess. Also how sure are you of the amount of refrigerant is correct in the system?