HK Trucking

Sounds to me like the power divider cams & wedges are worn to the point that they are jumping over on a hard pull, or, you've got a mismatch in tire diameters from the front drive axle to the rear drive axle. This has been discussed quite a few times previously on here, I'll see if I can find some of the threads & I'll post links to them

Yup! Just like Larry said, take it right up against the governor (2100 RPM) before upshifting. Those motors were made to be run that way, lugging below 1500 was a no no. Upshifting the compound is easy, waiting for the RPM to drop the correct amount (about 900 RPM) to upshift the main will take practice. If you get messed up, just think to yourself "what gear and what RPM would be appropriate for the current road speed? Then get your RPM's to that point and shift into the appropriate gear. If the RPM's are at the point that they would be at if you were already in that gear, it has to and will slide into that gear. Downshifting will be just the opposite of upshifting, you take it out of gear, raise the RPM to the correct point and shift into the lower gear. I'm not referring to double clutching because I always shift without the clutch. Once you get the hang of it, it's like a 6th sense.

I was just thinking: With the push type double disc clutch, Mack used a clutch brake on the countershaft. Assuming it is still in there, you'll have to re adjust that clutch brake too after this is all said & done. If you look up thru the bottom inspection hole you'll see it, there's a 15/16 head adjusting bolt & jam nut on it. Adjust the bolt as necessary to squeeze the clutch brake at the bottom 1 inch of clutch pedal travel, then tighten the jam nut. .

Glenn, the last one of those push type clutches that I "unshimmed" was on a hot August day in 1981, in my B613T5466 single axle dump truck that I had at the time. I can remember it like it was yesterday. Yes, I have seen numerous TRQ7220 Quadruplex transmissions with the 14" angle spring pull type double disc clutch, the ones I dealt with were in DM611SX dump trucks. Oh, BTW, I'm "only" 54!!!!!!! .

Yes it's a push type. The release shaft is below the centerline of the trans, and the rod pulls on the arm, which causes the fork to push on the throwout bearing. It's definitely a double disc because the mounting bosses where the bolts attach the trans bellhousing to the flywheel housing are about an inch long. On a single disc bellhousing those bosses would be nearly flat. Also in that pic is the adjusting bolt with jam nut that I was referring to earlier, but yours must have been replaced with a conventional 3/4 hex head bolt at some point..

In a B model that double disc would be a push type, as opposed to the more modern pull type double disc clutches. First off, does the pedal have 1 to 2" of free travel at the beginning before you feel resistance? If not, then adjust the linkage at the clutch release shaft on the side of the bellhousing. It will have a 3/4 hex jam nut and a square head adjusting bolt. Loosen the jam nut and back off the adj. bolt til you have the proper free travel in the pedal, then tighten the jam nut. If the pedal already has free travel and the clutch is slipping, then you can take out the shims between the pressure plate & flywheel to get some more life out of a worn clutch. Take out the floorboard, take off the inspection cover on top of the bellhousing, and remove the pressure plate attaching bolts one at a time and take the shim out (the shims are washers with a tab that has a hole in it where you can hook a piece of mechanics wire while removing, so you don't drop a shim into the clutch or bellhousing), then replace the bolt Do not fully tighten any of the bolts until you have rotated the flywheel 360 degrees and removed all the shims, then go around one more time and tighten all the pressure plate attaching bolts. After removing the shims you will have to re adjust the clutch as I described previously. If you find that the shims have already been removed and the clutch is properly adjusted and still slipping, or, you cannot get a good adjustment, then the clutch is history and needs to be replaced. .

Yes, there is supposed to be an external return spring. Usually there is an "eye" for it to attach to that rod that hooks to the throttle arm, ans a bracket that sticks up from the top of the compressor with a hole in it where the other end of the spring attaches. Any generic throttle spring will work. Use the lightest spring tension possible which will pull the throttle back to idle. A too heavy throttle spring makes it crappy to drive and puts a lot of extra strain on the linkage..

If you're saying that the pedal & linkage is returning to the idle position, yet the engine is still racing, then check that the throttle arm has not come loose from the spline on the throttle shaft on the side of the governor. If that is loose, then the arm may have slipped on the shaft. If that checks OK, then you've got internal issues in the governor itself. I don't think it's a case of a stuck rack in the pump, or else the shutoff wouldn't slow it down.

I'd say the bottom end of the stick is worn to the point that it can jump out of one rail and get caught in between the rails when not shifted carefully. Back in the good ol days we used to carry a small pry bar in the truck for just such occasions. You have to stick the pry bar thru those 2 clevises that connect the compound shifter rails to the compound box and pry them into neutral, then the stick will be "unjammed" To cure the problem, we used to build up the bottom of the stick with a welder, then grind it off to the approximate original shape & dimensions so it cannot jump out of the rails. Until then you can also prevent it from jamming by shifting it "square", slide the stick straight out of gear, then across, then straight into the next slot. Don't push sideways on the stick when coming out of or going into gear. Hope this helps.

Those engines were never noted for their power output, even with a manual trans. Put an auto behind one and I think it would be a real dog (no pun intended). Since it's going to be a "toy" truck not pulling heavy loads, how about a 6BT Cummins from a Dodge pickup, with an automatic? . I'm no fan of automatic transmissions, but if you really must have an auto, maybe that would be the way to go.

Bad idea in my opinion. .

You are very very lucky that tha pitman arm didn't come off the shaft during one of those "shaking" episodes at 30 - 50 MPH, or quite possibly you wouldn't be here to tell us about it. I agree, the sector shaft & pitman arm are likely junk after being run loose like that.

BTW, that shift pattern diagram plate in the earlier post is for a TRQ7220.

The TR72 main box is direct in hi gear, as opposed to the TR720 main box being overdrive in hi gear, but since leversole's transmission is a TRTL72, then it's a "single overdrive" triplex because hi split is overdrive in the back box. A "TRT(L) 720" would be a "double overdrive" triplex because the main box is overdrive in hi gear and the back box is also overdive in hi split.

I'd be very careful even just airing up a tire that has been run flat. The steel cords in the tire may be damaged even though there is no damage visible externally. Damaged cords + inflation can = BANG!!!!!!!!!!! And it ain't pretty when a tire explodes while you're inflating it. .

I've done that too, I had some stuck so bad that with a jack pushing up on the sleeve remover tool from the bottom, the front of the truck was off the ground. I let the pressure off, wrapped the crank journals with wet rags covered with aluminum foil, then welded a few beads inside each jammed sleeve with a wire feed welder & let it cool. When I started jacking again, they popped loose & continued sliding out rather easily.

There's an old unwritten rule: Never get your biggest machine stuck!!!!! LMAO!!!!!!!!!

That's the power steering pump setup that was used on the early DM & R models.

Amen to that! I've been on a downhill slide for 4 years now!!!!

The pins & linkage that connect the governor to the rack are worn and sloppy allowing the rack to slide further open, especially if the truck is nosed downhill. Pull the pump & get it rebuilt ASAP, because if the governor linkage comes completely apart the engine will run wild with no control over RPM, and no way to shut it down except to stall it out or pinch off the fuel suction line.

Looking closer at the original post, it appears that truck has a Sheppard power steering box, and I see it has an alternator with no power steering pump drive on the back of it, so I'm guessing the P.S. pump is driven off the back of the compressor.

No, you can't change that engine over to full flow spin on filters for the reasons previously stated. Regarding the LH starter location, I've seen B61SX that had the power steering driven off the rear of the air compressor with that old 2 belt drive. They had the starter on the left side because there was no room on the right with the P.S. pump there. Ir was an OEM factory setup, not changed later.

Nice photo! Now that's a real truck!!!! The green & red seemed to be an east coast thing back in the day. I'm originally from CT, and my trucks uere green with red hubs, both the trucks I had in CT, and the ones I had here in WI. .

In 1980 the flat stainless with the 1/2 bulldog was OEM. I worked for AC&S Excavating in Pound Ridge NY at the time, they bought new 1979 & 1980 DM686SX triaxle dump trucks and that's the type of mirrors that were on 'em.

This wouldn't be desirable for a restoration, but I used to use 2" fire hose. Cut 2 pieces of fire hose the proper length, then slide a hose over each strap, put the straps on & tighten down. Youll never have a tank insulator problem again. Crude, but effective. .