Geoff Weeks

There may be a "European" bolt pattern disk hub that will carry the big bearings. Plenty of disks made for those hubs, but still not what I'd call common. That said, I wouldn't have made the change to begin with.

Brocky, I can see where flipping something on the dash might throw off timing. On my K's I pre-select,so on upshift there is already vacuum at the diaphragm, and once torque load is off the gears the shift takes place. downshift is a little more tricky, as you have to "break torque and quickly raise the engine speed to complete the shift.. Both ways are pre-selected. In the Marmon, with the gov diesel, it is a little easier to control the engine rpm, than it is with carb'd gas.

My Marmon has two speeds front and rear on the tandems. Air shift (piston type) and never had a problem, always shifted when I needed them to. I started out in low every time, they got used alot.

That is not a Loadstar, it is a V model. BTW I maintained a Loadstar school bus on air brakes, you could get a Loadstar with air brakes, just as you could a K-7 (around the same GVW range) and all "midrange" IHC's. Juice brakes were more common, but air was an option.

With any two speed you are not going to have lightning fast shifts. Air and Vacuum, use air pressure as a cushion, Electric needs a torsion spring. (note early diaphragm air shift also used torsion spring) that is known to break without warning. I have two single axle on vacuum shift and one tandem on air (piston type), I find both reliable and easy to "learn" My air shift is electric over air, air solenoid controls air pressure to both front and rear axle shift motors (pistons). The two vacuum shift are cable to valve with no other power needed.

Right kind of wheels, non syncro, 2 spd rear.... Life is good! Air, electric or vacuum on the 2 spd shift motor? Air is my 1st choice, vacuum 2nd and electric last.

Which side of the seal is it on? That looks like it could be a "weep hole" to allow any coolant that gets by the face seal to drain out and not destroy the bearings, also to vent air from the bearing cavity when there are temp changes. If you have a lot of coolant leaking from it than the face seal is shot. If I am wrong and it is on the impeller side of the seal, then disassemble, clean the casting and braize shut.

Not really, These trucks were used to pull semi trailers after WW2 when trucks were in short supply. They were geared to run 55 @ rated RPM. Mine will top out at 62-63 at redline. Smaller, lighter trucks were sold to small farms, etc had the flathead, and were more 45 mph trucks. The -6 and up had IHC designed OHV engines, lined blocks (for easy overhaul) and were trucks from the get go. I can only conclude they didn't understand the dynamics of driveshafts turning at high speeds. Like the OP'ers truck, it was designed for longer trips on hiway.

I was chasing a bad vibration, I used to be able to run the truck at 50-55 and it was un-drivable above 35. The rear shaft had bowed badly, not from any hit but from running above the critical speed. The more a dove into the problem, the only thing that made sense. I started laying out a replacement shaft and once I ran it through the Spicer calculator, I found stock would not work. The hard part was U joints were obsolete and I had to switch to a more modern joint. That meant changing yokes and had to make the tube a lot larger to make it stronger. Ended up putting more in the shaft than the truck cost me 20 years ago!

One thing I found working out a new driveshaft for my K-7 that early on and I don't know when it was learned, that driveshafts were made that were well into and above the critical speed. My K-7 had the OEM shaft , I checked against the parts list and dimensions, it was as built. I then plugged those very same dimensions into Spicer's calculator for critical speed and it was in and above during most of highway running. I had to re design the shaft to make sure I stayed well away from critical speed. I suspect that the people mentioning not running the rear in low with the trans in O/D is because if you are pushing the driveshaft into critical speed it can whip and come apart. I don't know when the effects of critical speed and 1/2 true critical speed were fully understood, I knew of critical but not 1/2 true and didn't know how to determine it. Spicer has a calculator on their website that makes it easy, plug in shaft dimensions and it will spit out the rpm's to keep away from.

No reason you can't run low rear in O/D front. The rear doesn't care, a worn driveshaft might as you are pushing it at its fastest speed, something not always done in high. It would be like saying you can't run any rear fast. It isn't the rear but the driveshaft that has limits. Run a rear real fast and you'll have heat issues, but unless it already has a problem, it will not make one. Without knowing the trans ratio it is hard to say what is "progressive" and what is not. My K-7's go 4-lo, 5-lo, 4 hi 5 hi (working 5 speed) but I find the steps too close together to be of much use, with a big step between 3hi and 4 lo. I ran my Marmon with a .73 od in top (15 O/D) in low but had to be careful not to push the driveshaft speed above critical speed. When I would feel it I would upshift the rear and down the main. Really pulling hard in 15th low, was close to 14th (direct) in high, but there was a slight difference, nothing the 3406B couldn't deal with.

At least you had a good portion of the root of the tooth to work with. What did the pinion look like? Most times I have seen damage like that the pinion took the worse of it.

Off topic but... Years ago I was working on a large NG boiler. It hadn't been in use for a while and once it was repaired wouldn't fire up properly. It would light off and the main gas valve started to open, got about 1/2 way and then stopped. Guy I was working with determined that the valve was hyd operated, and was low on fluid. He pulled a sample and said "this smells like nothing I know". I took a sniff, and knew I smelled it before, It took a while and then it came to me Skydrol! it was over 15 years since I had been around it. Made sense, fire resistant hyd oil! Sent him off to Midway airport for a pint, problem solved!

Cat and Cummins both return above fuel (just an open dump in the top of the tank) I can't say for sure on Mack. At least on the older mechanical engine like we are dealing with here.

As far as I know Detroit two strokes are the only common diesel that returns to below fuel level. It done so because the Detroit system is just a loop with a restriction. Cat and Cummins and I assume Mack (I don't remember looking at a Mack tank) all return to the top of the fuel tank and are open to air so are an "air leak". There is no check or other valve that keeps air out of the return. Air in the suction line will make its way to the highest point in the fuel system and can cause a no start. the return line is always open to air (except Detroit 2 strokes)

Old truck= old fuel hoses. I have chased my tail looking for a problem only to find the hose was porous and would allow air in but not fuel out. When in doubt, I would replace the suction hoses from the tank to the lift pump before going further. Funny thing is they can leak air and not show a drop of fuel from the outside.

BTW you front hubs have the correct large "wedges" to be used on wide rims, 8" flat based (tube type) or 9" 22.5 tubeless rim. The wide rims need the long triangle wedges to keep the rim from breaking the studs.

I had two cabovers (IHC's) that had powerpacker pump and "over center" long cyl. They had the cross checks, and I had one leaky cyl, so had to often add fluid, and I found if it was wet petroleum product, it would work. I would use anything and it worked. ATF, PS fluid or 10W-30. never had any opperational problems because of fluid type.

8.25 rims are generally limited to 7k lbs, so if you want the full weight capacity of the tire size, you need the wider rim. Most often tires have a "spec" rim size and "acceptable" rim size which is often 1 size narrower or wider than the spec rim. So if you aren't going to load the rim above its limit, then 8.25 is fine if it is shown as an acceptable rim. I ran 295/80 22.5 steer tires, they are the same size (diameter) and just a hair wider, then a 11r x 22.5 and can be placed next to them in a set of duals, but have a higher weight capacity and to use that extra weight, you need to use 9" rims. Before someone says "those aren't the same , they are low pro 22.5," look up the tire size exactly as I wrote it. They aren't the more common 295/75 x 22.5

10x20 is equal to a 11x 22.5, 11x 20 is equal to a 12x 22.5 Not sure what you are asking, 22.5 tubeless rim fits a 20" spoke. So a 11x 22.5 and a 10x 20 both have the same outside diameter, width and load carrying capacity (assuming the same load range or ply rating). The sidewall on a 20" tube type is taller, the outside diameter of the tubeless and tube type are the same. Tubeless require a drop center rim, (unlike the flat base of a tube type) so the rim is larger in diameter to allow for the "gutter" in the center of the drop center rim. On a tube type the rim comes apart to slide the tire and tube into place, a tubeless doesn't come apart so there must be a gutter to allow the beads to be forced over the rim.

No, what I am saying is to go from tube type to tubeless and STAY THE SAME, in terms of size in every measure, you must add 1 to the size and 2.5" to the rim diameter SO a 11x 20 is equivalent to a 12x 22.5, not a 11x 22.5, which is the same as a 10x 20. If you downsize make sure the load capacity of the tire can handle the load, it will also throw off the speedo.

doubtful the viscosity of the fluid is causing you problem, The gravity down is the problem, that should not happen on a modern (somewhat) truck cab system. It can trap a man under the cab and crush them if something goes wrong. Somewhere in the system there needs to be a cross-check valve that will not allow gravity to move the cab, it should require pressure from the return side (the side of the piston that is "retracting") to open the check and allow fluid to return.

Again, when changing from tube type to tubeless, you add one to the "size" so 11 tube type becomes a 12 tubeless and you add 2.5 to the rim diameter. So a 11x 20 becomes 12 x 22.5 to remain the same. 20" spokes can have 20" tube type (flat based) rims or 22.5 tubeless drop center rims.

Here are some choices, note the "heavy duty" flange head for front or single aluminum wheels 100AB.pdf

As you have said, it really doesn't matter what form of RTV is used, some are worse than others, but the fact it can glue the cones in place. I used to buy the gaskets 25 at a time, and still have some on my wall, after retirement. IHC and a few others use 3/4" studs through straight holes (no cones) and those you can use RTV, but I still use gaskets.