Geoff Weeks

If you pull the delivery valve spring out, you don't need to pressureize it, just enough (a drop tank held above the height of the pump will do) so the fuel runs out. When the plunger closes off the supply to start injection, the fuel will stop coming out the port. The CAV DPA's on the Leyland 680's were supposed to have a "double spline on the coupler (just a roll pin in a hole in the spline) but a few came through without it being there and we had to spill time them.

Likely the OCD in me, but I despise Kludge on top of Kludges. The way that one is mounted, by the main housing to the frame, depending on how much room is "behind" it, it may be possible to remove the rear cover, and pull the shaft back through enough to re time. You'd have to lock the main gear at the mid point, then re orient the shaft so the mark is in the right place and re-install, for good measure reach in with a die grinder and make a new timing mark. If you just make it work by grinding off the double spline, and someone comes along and pulls the arm for some reason you back to where you are now. It is like a Cummins where someone pull the accessory drive off, and then re installed without timing it. It will work, but the next poor soul that has to run the overhead will find (after much work and frustration) that the timing marks aren't timed to anything! Fix it right once and it will be right, for the life of it. Don't and it will be wrong the entire time it is in service. Not like he has to get it together to move a load on Monday!

Mecho, May be I am mis-remembering but on my 392's (and others) there is a skip in the spline, and the arm will only go on in one of four positions. So you can't just put it on in any position. The internal timing marks set where the external marks are. If this 392 is retro-fitted to a 1966 truck, It is impossible to know if it was ever set up correctly. The Sheppard 39 not the 392 was the box that was out in the 60's. The end of the pitman shaft has a small section that looks like it has been ground out, possibly to remove the "double spline". If someone modified it to "make it work" and the next guy came along and lined up the external marks, that lead to the turning tighter in one direction then the other. If the double spline has been removed, then center the gear, center the tires and put the arm on. If the spline is there, you have to decide how you want to fix it. The reason there are timing marks, both internal and external is that the gear is set-up for a specific application, and in the application, if you assemble "in time" it will be factory correct, the only alignment adjustment (from the steering box point of view) is the drag link adjustment. When you go your own way, and make it work, without then leaving a record, by putting new timing marks, you can end up like Bob has, where assembling to the correct mark leaves you in the wrong place. If Sheppard is contracted to supply a steering gear, they will know the angle of the box on the frame, and time the internal gear so the external pitman arm will be correct, the internal gear will then have a timing mark on it to mesh with the rack gear timing marks and a unique build number will be stamped into the housing for that build. I think in Bob's case a 392 gear from some other application was used to replace the 39 that a 60's truck would have or even a manual box. The "correct" fix, would be to lock the main gear at mid point, remove the rear cover, pull the pitman shaft back and rotate until the external timing mark was as close to vertical as you can get (this is one reason why the pitman arm can be fitted in 4 places, so you can get the mark exactly where it needs to be, splitting the move of one tooth on the pinion gear into 4ths), and mesh back into the box, grind a new timing mark on the pinion gear, then re assemble. That does not sound like what was done when this box was originally fitted.

This is what I'd do: center the steering box at the mid point in its travel and lock it there so it can't drift down on its own. Pull the drag link off the pitman arm. Install the pitman arm on the shaft with the punch/timing marks aligned. See how much change in the drag link is needed to hook to the pitman arm with the wheels straight forward. From one of the pictures it looks like the drag link is two tie rod ends with an adjusting sleeve in between. That should give a fair amount of adjustment. That is how my Marmon is set up.

I suspect your "turn sharper" one way then the other, is what you suspect. Someone screwed up and covered it up by adjusting the heck out of the drag link. From what I remember, the pitman arm can go on the shaft in four places, 90 deg apart. So line up the pitman arm to the closest place it can go on with the box centered, should have punch-marks, then adjust the drag-link so the wheels are straight when the box is at mid position. Since the 392 box post-dates when that truck was built, it is hard to know if when it was fitted, the person doing the fitting did the job correctly. From what I remember there is a double tooth on the pitman shaft spline and a corresponding gap in splines on the arm every 90 deg. It has been a few years since I did one.

The bottom kit in the screen shot likely has all you need. Again, these are R-12 kits and I haven't tried them on an ATR as I have nothing as new as to have traction control. It is the kit listed at Fleetpride, but I have seen them cheaper.

https://www.fleetpride.com/parts/bendix-relay-valve-5019003?srsltid=AfmBOoothJ8GDJg5FZA9xm-PFx7lUT3MHqGVL2fMJo4I9uhXx-RcOAt0 https://bigrigworld.com/r-12-valve-maintenance-kit-5002831bxw.html?srsltid=AfmBOorwRZIJ1V-s0PH8OMLysX30eh69XQT-XgBUVncCZS3TOPnO3KjJ

Since this valve appears to be a modified R12 relay valve with a different housing and top cover, I would guess one of the maintenance kits made for the R 12 would fit, with the disclaimer that I have not tried it and it is "at your own risk".

You could get a couple of really long bolts, cut the heads off and make "alignment" studs to get you started. Yeah, those 392's are HEAVY! I have installed on my 9670 by myself, but they bolt on the outside of the frame and don't have those spacer blocks to contend with while trying to get the bolts started. Still a bear of a job.

In this exploded diagram the possible leak points not including the solenoid valve are: 1) between the top face of part #6 and the body of the valve. Look for crud stuck in this location 2) O ring #10 seals valve # 6 to retainer #11, a bad O ring here would leak out the bottom 3) A bad O ring #9, unlikely as the is a stationary seal between # 11 and the valve body. Of the three situation #1 is the most likely, followed closely by #2 O ring # 10 has to seal # 6 which slides in the O ring when valve #6 moves off its seat. When at rest (no brake applied), any pressure in the outlet port vents out the center of part #6.

All the outlet ports are marked with a red X

The two pipes go to ABS actuator valves then to hoses to the brake chambers, Make sure the brake chambers aren't backfeeding. The ABS valve on either side are just straight through unless the ABS is in action. The 3rd hose on the bottom should go to a quick-release on the spring brake circuit to prevent compounding (anti-compounding QR) . Any of these could backfeed it there is a problem "down stream" all would only leak back when the parking brake is off. If your valve leaks with the parking brake on, then it is the valve itself. If it leaks all the time, whenever there is pressure in the air system, it is most likely the bottom portion of the valve, which can be taken out and cleaned and new O rings install by removing the snap ring (spring loaded parts behind the snap ring, so be ready to ketch them. There is a small chance that solenoid valve on the top has a small leak, and I think that would be harder to repair/get parts for. For the cost of O rings, I would start at the bottom of the valve, if it leak all the time there is air in the system (parking brake on or off)

That Bendix number come back to the ATR-6 which is what I posted the manual on.

In the link I posted to the Bendix "manual" on that valve, it is all just plain O rings, and the manual even lists the size, so you can go to where you buy O rings, and have them all before you start. There is a small chance that there is a small (internal) leak from the solenoid valve on the top, but think it is much more likely a piece of crud is stuck in the valve, disassemble, inspect and install new O rings. Cost would be the cost of the O rings, but if you have a good supplier, then less than $20 would be my guess. Follow Mecho's testing to make sure it isn't some other valve backfeeding into this one. edit: If your a gambling man, leave the valve in place, don't mess with the top 1/2 and only take the snap ring off the outlet, and remove and replace the O rings that come out the bottom, clean the valve seat where the delivery valve seats. That is the most likely point of failure. Just two O rings.

Not really, if you changed the whole chamber, with a service 30/30 you will be changing the correct part. I still have E brake chambers that you can service the spring brake side, either diaphragm or piston type, but those are what? 30-40 year old? When did the "idiot proof" "sealed chambers come out? Diaphragms leak to the outside, the piston rod seals leak chamber to chamber, but with the idiot-proof chambers, the only way to fix is to replace the service 30/30. In the old ones you can take the big Phillips head screw off one piston, remove the interchamber rod and replace the seals, though not many did.

If it is infact the valve, most of the likely O rings and any dirt on the valve can be reached from below by removing the snap-ring and delivery valve. The O ring sizes are listed in the Bendix breakdown I posted.

It will not be a diaphragm, they leak externally, it could be the O rings on the piston shaft of the maxi section, they can leak from spring brake air pressure into service brake side. Without knowing where the other line on the valve goes, I can't say what it could leak back. Might be inversion valve or anti-compounding.

The big "green" line closest to the camera should be supply. The 3/8" line near the top should be signal. It would appear the valve has 4 outlet ports, two on the side and 2 on the bottom. In the picture one of the bottom ports is plugged and it looks like the line I asked about goes into the other bottom outlet port.

In the pic, there is one line that appears to be hooked to the outlet of the relay that is not connected to a ABS modulating valve. Where does that one go?

I thought of asking, but a test of the output lines would give a good indication. Not being 100% sure of what the valve is hooked to, knowing when it leaks needs to know how it is used. K.I.S.S., if air is leaking back through the output, how the valve is used, is not important, it isn't the problem.

I think the two valves are more or less the same. The one with the solenoid on the top cover allows it to be used with traction control, the other is ABS only, as it requires treadle valve pressure to operate the relay portion and the ABS actuators are on the outlet. The ABS/traction control version allows the traction control to open the relay valve independent of the treadle valve, then the ABS controllers work and apply brake pressure to the spinning wheel and keeping it from the non spinning. The solenoid valve take tank pressure to operate the relay to "full open" while simultaneously preventing signal pressure back up the treadle valve line and out the exhaust at the treadle. regardless, I'd want to make sure none of the delivery lines are some how feeding air back up to the valve. Any air would vent out the exhaust of that valve giving the impression that the valve is "bad" when in reality it is doing what it is supposed to, vent any pressure from the brake lines when not called for by either the treadle valve or the traction control solenoid.

Don't think it is,there is an electrical connection on the top from what I can see. Needs to be better I D to be sure. Looks an awful lot like a traction valve. I could be wrong.

Hard to say for sure, but looks like this is the valve. Ad for picture ID only. https://www.ebay.com/itm/305180616028 Parts breakdown and procedure: BW2598.pdf

1st order of business is to make sure it is the valve that is bad. Remove the outlet hoses/piping and see if it stops leaking and air is coming back up a line from a defective brake chamber. Far better to find that out now, not after you have spent the $600 and wrestled it out of there.

I would try that 4.10 before changing anything. 4.10 with .73 OD on 20" rubber is where I ended up, and liked it a whole lot better than the same with 3.90.