HK Trucking

Makes you wonder why the previous owner didn't reconnect it properly. Why do some people feel the need to do things half assed and cause a truck to become a cobbled up mess after a few years? I've never been able to grasp the rationale behind that thinking.

Nice B81 in your photo^^^^^^^^^^^. That was when Mack made REAL trucks.

Good thing you got those injectors out of there Rob. Next thing you know, a piston would have a hole melted through it.

I'm reaching way back into my memory banks, but IIRC, it was the Sheller Globe Co. that built the R, U, & DM cabs, and the Chicago Manufacturing Co. that built the B model cabs.

Jake brake switch. It would be mounted at the throttle lever on the injection pump. When the throttle returns to idle the throttle lever contacts the switch causing the Jake brake to come on (provided the dashboard switch is on and the clutch pedal is all the way up).

Air ride on a dump truck is a complete disaster. I had a CL quad axle on air ride a few years ago (the one in my avatar) and it was the biggest PITA I ever owned, didn't keep it around here for long. Just as Glenn said, as soon as you go off the road, the suspension can't react to uneven terrain, and you get wheel spin, then when the spinning wheel connects with the ground again you get shock loading of the entire drivetrain. Very tough on differentials & axles. We always had to lock the power divider as soon as the truck left the blacktop, this helped some with the wheelspin issue, but when you think about it, having the power divider locked whenever the truck is off road concentrates twice the torque on the axle which still has traction, again leading to extreme stress on the driveline. When dumping, you'll have to dump the air out of the air suspension to stabilize the rear of the truck, and even then, an air ride dump truck is more prone to tipping over than one on springs. You can set it up so that the air automatically dumps out of the suspension whenever the PTO is engaged, that way the driver can't forget to dump the air before raising the dump body. I know there are guys out there that will say they love having air ride on a dump truck, and I can see how it might not be bad if the truck is always on a hard flat surface, such as hauling asphalt, but in the type of work my company was doing, it was useless.

Mack Green 40496, and Mack red 72182. These are PPG numbers, PPG (formerly Ditzler) was the OEM paint supplier to Mack trucks at that time.

What happens if the driver is of some other religious persuasion????? J/K Thad.

Just off the top of my head I can tell you that a U686 would have an ENDT676 285 HP Maxidyne and a TRL 107 5 speed, and most of the ones I've seen had Mack 34,000 lb rears on camelback. R690 would have an E7 Maxidyne engine, usually a 300 HP. In one of your other posts you stated you were looking at a 1967 R model. Did you mean R609? If it's an R609 it would have had an END 711 thermodyne originally.

It's really a shame that it's a bygone era isn't it?

Did it just die suddenly on the road, or was it running OK when parked and then wouldn't start the next time you tried it? If it just died suddenly on the road, check to see if the fuel pick up tube in the tank may have cracked or broken off. About a month ago one of the IH semi tractors at work quit suddenly on the road, the fuel tank was 3/4 full, tried to get it going by filling the filter, but it would just run for a few seconds until the filter was empty again. Anyhow, we put it on the lowboy trailer and hauled it back to the shop. I hooked up a temporary fuel suction line and stuck the end of the line down into the fuel tank thru the filler neck, and the truck ran OK. This suggested that the pickup tube in the tank was defective. Pulled the tank, and on the IH tank you can unscrew the pickup tube and remove it from the tank. The pickup tube had fractured right at the very top and fallen into the tank, so even with a full fuel tank, it couldn't get fuel. I made up a new pickup tube from a piece of electrical conduit and brazed it to the pipe fitting that attaches it to the tank, installed it and reinstalled the tank and all was well. I know that most Mack tanks have the fuel pickup tube welded into the top of the tank, but if that turns out to be the problem, it's possible to use a hole saw and bore another hole in the top of the tank, weld in a female pipe fitting of the correct size and fabricate a screw in pickup tube as described earlier. That would be a lot better than buying a new $800.00 tank just because the pickup tube is bad. Note - If you're not sure of the proper safety procedures for welding on a fuel tank, have it done by someone who is.

Bullsh*t.

I think it looks great just the way it is. If you're concerned about the faded paint on the hood either buff it out or repaint the truck with the same color scheme. Green & red are the ultimate classic Mack colors. (Of course my opinion may not be entirely impartial) lol.

Happened to see this on another forum: http://www.redpowermagazine.com/forums/ind...showtopic=34136

The Quadruplex transmission.

Are you sure that what you're hearing is not just normal diesel combustion rattle? Those engines normally do have a definite combustion rattle when you crack the throttle or accelerate. That would be pronounced on acceleration, and does sound similar to the spark knock of a gas engine with overadvanced timing. Also, in the 1990's, Mack began producing a revised replacement piston design for the 237 and 285 engines which caused more of a "combustion knock" than the original design. Mack issued a service bulletin at that time about the revised piston design and increased sound levels, maybe someone else here would still have access to that service bulletin. I used the OEM overhaul kits on a couple of them back then and I did notice the increased combustion knock. If your engine was overhauled with a Mack OEM overhaul kit with the new pistons, maybe that's what you're hearing? None of us can say for sure without observing it in person, but before you go on a wild goose chase and tear it apart, make sure there actually is a problem. Overadvanced injector pump timing can also cause excessive combustion knock, so a timing check is in order.

Merry Christmas & Happy New Year to all of you.

Here's a previous thread on this subject: http://www.bigmacktrucks.com/index.php?showtopic=2542 Hope this helps.

A transverse torque rod attaches to a bracket on the rear drive axle housing and is also attached to the right side frame rail to prevent sideways movement of the axle. If all parts of the suspension are in good condition, this prevents the entire tandem from moving sideways, but if the trunnion bushings and spring box pads are worn then even though the rear axle is held straight, the front drive axle can still move around. In trucks with the pressed steel rear axle housings and the transverse torque rod, there is a high incidence of a cracked axle housing on the left side in the area where the differential bolts into the "banjo" housing, due to the sideways loading imposed by the transverse torque rod. The first symptom of a cracked axle housing due to this scenario is an oil leak on the left side at the interface of the differential housing and the axle housing.

Does your truck have the transverse torque rod on the rear drive axle? If so, that's why the rear axle is staying in line while the front one is moving sideways. In any case there has to be looseness somewhere that is causing this, either in the trunnion bushings or the spring box pads. Also, there are spring box pads with offset dowels to change the axle alignment if needed.

Air shift cylinder needs a rebuild. This problem frequently shows up when the weather starts to get colder causing the "O" rings on the piston in the range shift cylinder to shrink and allow air to blow by. It can be fixed while the trans. is in the truck, not a big deal, but I would suggest fixing it sooner rather than later, because damage can occur to the range shift if it continues to repeatedly jump out of gear.

Other than the self locking adjusting nut, everything is the same as a conventional wheel bearing setup. Run the nut up tight, spin the hub a few times, back it off, run it up tight again, spin the hub and back off the nut til you have the proper bearing adjustment, then make sure the lock nut has clicked into the lock position. I've never run across one with a crush sleeve yet, but all the stuff where I work is 46,000 lb axles. Is that crush sleeve used on the lighter OTR type axles?

On a 75 DM with 2 tanks, there is (or should be) a crossover line running from the lower front of one tank to the lower front side of the other tank. The suction and return lines for the engine are on the driver's side tank. If it empties the driver's side tank and the pass. side tank stays full, then one or both of the shutoff valves (located where the crossover line hooks to each tank) are closed, or there is a blockage in the crossover line or fittings.

No Glenn, there is no spacer. The nut just goes right up against the outer bearing. The inner part of the nut has a notch to engage into the spindle to prevent it from turning, and the tabs on the sides of the nut are connected to prongs that pop out and lock the threaded part of the nut to the inner part of the nut, keeping it in proper adjustment and preventing the nut from coming loose. That's why it's necessary to use the right size socket and depress the tabs properly to remove the nut without damage.

A while back there was some discussion on the board about disconnecting batteries when welding on trucks or equipment with electronically controlled engines. At the shop where I work we have this: It's called an "Anti Zap", you just connect it to one of the batteries (no need to unhook the battery cables) and it supposedly absorbs any stray voltage or power surges. There's a green LED indicator on it to assure that it has a good connection and the system is protected. It's made in Australia, the one we have is for 12V use.