HK Trucking

Over the years I had 3 DM 690's here with that engine, they each had the T2070 7 speed and 5.73 rears. According to the Mack specs the operating range is 1020 to 1750 RPM's In a dump truck application those engines were useless @ their stock RPM limit of 1750. Each one of them got "adjusted" to run 2100 very soon after arriving here. I'm not disputing that they work well in a highway application, but I can say for sure that in a dump truck a 1750 RPM limit just doesn't cut it.

And once you get it set where you think it should be, be sure the driveline angles are OK. Too much of an angle due to improper ride height will wear out U joints and create vibrations which can lead to rear end and transmission problems.

As Maxville said, check your throttle linkage first. Have someone hold the accelerator to the floor (with the engine off) and check to see that the throttle lever on the side of the governor is contacting the stop screw (wide open). If it is not, then find the problem with the linkage and fix it, could be worn ball joints , a bent rod, stop bolt under the pedal set too high, worn actuator arm at the governor etc. Once you're sure the throttle is opening all the way, check your high RPM setting. The EM7 engines were originally set at 1750, but they were completely gutless at that setting and just about everyone turned them up to 2100. You can raise the high RPM's yourself by loosening the jam nut on the high speed stop screw where the throttle shaft enters the governor, and turning the stop screw to allow the throttle shaft to go further in the high speed direction. If these hints don't work, then you'll have to pull the pump and have an injection shop set it up for 2100 RPM's. I had a couple of trucks with the EM7-300 and T2070 which also has the .60 to 1 overdrive. Mine both had 5.73 rears and with the RPM's @ 2100 in high gear they would get close to 70 MPH.

Guess I missed that part in the original post. Remove the seal and throw it away. Inspect the bearing cups and cones and replace if necessary. Lube the inner bearing and set it in the hub, then install a new seal. Once you've removed a hub, never reuse a wheel seal.

place one of your tire & rim assemblies on the floor so the convex side of the rim is up. Place the hub face down (like it is in the pic) into the rim so the studs are thru the rim holes. This will anchor the hub so you have something to pull against. Now take a hook bar and get between the seal and the bearing and pry the seal out of the hub. That's how I do it with unimount hubs which are pretty much the same as what you've got there.

I used to (when loaded) start out in 1st lo split, shift compound to hi split, take both sticks out of gear (with 2 hands)go to 2nd lo split, then go to direct, then hi split. To shift out of 2 hi on a gradual grade (not a steep hill) , when engine is against the governor in 2 hi, pull both sticks into neutral, put compound into direct then main into 3rd. Downshifting under pressure on a hill: For example lets say you've got the truck rolling pretty good in 4th hi. When tach touches 1500 or so, pull compound out of hi, put throttle to floor, and compound should slide in to lo split. When tach again touches 1500 pull both sticks out of gear, put throttle to floor and both sticks should slide in to 3rd direct. When tach again touches 1500, pull both sticks out of gear, put throttle to floor and both sticks should slide into 2nd hi split. when tach again touches 1500, pull compound out of gear, put throttle to floor and compound should slide into lo split. Once you're in 2nd lo split, if you don't think that's gonna be a low enough gear for the hill, better just get the main into 1st while you've got the chance! These tricks were the way I did it in the hills of CT and NY with B models and early DM's with quad boxes. Just about every 2 hand split involved both sticks being in neutral simultaneously, but once you get some practice, it can be done as smoothly as an automatic. If your truck is on 24" rubber and your top speed with a quad box in 5th hi is in the lower 50 mph range, I'd bet it has 8.24 rear axle ratio.

Heat the rim in the area around the hub hole with an oxy acetylene torch. This will expand it slightly. Then keep trying to hammer or pry it off like you've been doing. When re assembling, put some never seize compound on the rim/ hub interface so you don't have this problem next time.

ENDT 675 or EM6 - 237. on the ID plate on the right side of the engine. It's the same size externally as the 707 gas engine. 672 cu. in displacement, 237 HP., 906 ft. lbs. torque.

Trunnion Bushing. The rubber type. Yes, I've changed them. Jack up the truck, put blocks under the trunnion. Remove the wheels from the rear axles on that side. Put a jack under each spring box on the side that you're changing. Since it appears that someone has put a home made retainer on the end of your trunnion shaft, that must be removed. Cut off the U bolts that hold the spring to the saddle. Remove the bottom half of the trunnion saddle. Jack up the rears so that the upper half of the trunnion saddle separates from the trunnion bushing. Remove the worn out rubber bushing from the trunnion shaft. Be sure that the trunnion shaft is clean and no pieces of the old bushing are stuck to it. Using some waterless hand cleaner as a lubricant, slide the new rubber bushing on to the shaft, center it in the middle of the area where the old bushing was. Let the rears down so the upper saddle contacts the trunnion shaft. Install the bottom saddle on the trunnion, install new U bolts, and tighten. Replace the home made retainer on the end of the trunnion shaft. If I remember correctly the torque spec for those U bolts is well in excess of 1,000 ft lbs. so if you don't have a torque multiplier that will achieve that torque, have the U bolts torqued at a shop with the proper equipment, this is very important. Insufficient torque on the U bolts can lead to broken spring centerbolts, and broken U bolts, and possible damage to the truck and personal injury.

No David, it is not.

Rob wrote: Amen Rob. That is the problem, some truck owners and drivers are all too willing to cut their rates just to stay busy and take work away from someone else. But what is the point of that? The reason for operating a truck is to make money and if they operate so cheap that they're just breaking even, or even losing money just to stay busy, that just ruins the market condition for everyone else who is trying to keep their rates up where they can make a profit. The contractors who hire the trucks are laughing all the way to the bank, depositing all that money they saved by getting the dump truck guys to work cheap. In effect, the dump truckers who cut rates and work cheap are just subsidizing their customers profit margin, while slowly bankrupting themselves. For 19 years when I was in the business, I tried to keep my rates where I could turn a profit. The last few years, with fuel cost skyrocketing, insurance and everything else going up, rates stayed flat, and if I tried to raise it to cover the increased costs, the contractors just said no and hired someone else who evidently didn't have sense enough to raise their rate when their expenses increased. My company always provided good service, always on time, experienced drivers, trucks available 7 days a week etc, but none of it mattered, all the contractors cared about was price. I'm glad I sold all my equipment when I did, because from what I've heard nothing's changed this year either, they're all just running for fuel money. This is way off topic and has nothing to do with head gaskets, so I'll end my rant now.

The reason for this is that the shops and mechanics are not all continuously cutting each others throats to try to steal work from each other. They set their rate at a level where they can make a decent profit, and that's it, it's not open for negotiation. There's no reason that trucking should be any different, the rate should be at a level where the truck owner can make a good profit, and the driver can be paid a fair wage with benefits. We know this isn't the case however, as truck owners are whipsawed against each other by their potential customers, rates have been driven into the toilet just about everywhere. The strange thing is that so many truck owners willingly participate in the creation of their own financial demise.

I hope they shimmed the rocker arm pedestals accordingly. There was a shop around here that was in the habit of milling the heads without shimming the rockers by the same amount, and within 5000 miles the valve guides would be wiped out. The geometry of the rocker arm is changed because the pivot point is moved closer to the camshaft when the head is milled. The rocker then tends to push sideways on the valve stem as it pushes it open, quickly wearing out the valve guides. If the rocker pedestals are shimmed, that prevents the problem. I've seen reman exchange engines that had the shims under the rockers for just this reason.

A vintage Mack engine to avoid???? Surely you jest!!!!!

Same thing. Mack changed the engine model designations in the early or mid 80's Or, if you want to get technical, it's the same as a EM6 - 237

E Tech.

V*!>0 will probably buy them, then eliminate them to further monopolize the truck market.

The older bellhousings usually had a small hole near the bottom where you could stick a large screwdriver into the teeth on the flywheel and by prying on the flywheel teeth you could turn the flywheel one tooth at a time. The E7's don't have this, and with those I put a socket and breaker bar on the harmonic balancer retaining bolt at the front of the crank and turn it that way.

Lets not forget the TRQ7220. .84 and .70 According to my reference materials.

The E7 came out around late 89, early 90 or so. E6 =672 cu. in. E7 = 728 cu. in. They made the E7 both mechanical and electronic up til at least the mid 90's, then all electronic. I'm not much into the V8's so not sure on the last E9.

Trent, I assume your referring to your B model here. Just look at a schematic of the wiring in your R model, that's got a relay (solenoid) which turns on all the switched breakers in the panel. Find the terminal on the key switch which is hot when the key is on, then run a wire from there to the small terminal on the solenoid which actuates it. The other small terminal on the solenoid must be grounded. Hook your main feed wire (from the batteries)to one big terminal on the solenoid, then run a wire from the other big terminal to the breaker panel. You'll also want some of the breakers to be unswitched (hot all the time) for headlights, turn signals, running lights, brake lights etc. Be sure to use a constant duty solenoid, those starter type solenoids will burn up quickly if energized constantly.

I think he's trying to break the news to us gently that soon, in addition to the camouflaged Volvo engines, Mack trucks will be equipped with Volvo cabs, but the Volvo cabs will be camouflaged with dashboards, door interiors and steering wheels with Mack Bulldogs on them. Wonder if it will have a slanted bar across the grille with a Bulldog emblem on it. Already done. You can't get a new Mack with a Mack engine anymore.

Install them the same way as the ones youre taking out. If there weren't any batteries in it look at the battery cable ends and see which looks like it would fit the smaller post, that would be negative, and the larger one would be positive. A more definite way to tell would be to disconnect the ground cables from the starter and using a long jumper wire connect a continuity tester from the starter end of the cable to the battery end of the cables. Whichever cable shows continuity with this method is the ground. 1968 models were positive ground when built, but as stated before someone could have changed it to negative ground since then. From what I've seen out there it appears Mack changed to original equipment negative ground about 1976 or 77

Sounds like it is out of adjustment, and probably all rusted up from not being used for a long time. A hard time crossing thru neutral from low to direct sounds like the gates in the 2 shift rails are not lined up properly. Get some PB Blaster and soak every clevis and pin on the shift rods between the shifter and the transmision, also spray plenty on the shifter mechanism itself. I'm not that familiar with your exact setup, but if there's a rubber boot where the stick enters the shifter, peel the rubber boot back and soak the ball joint there too. Now repeatedly work the shifter thru all positions to free it up. Once it is moving freely, check the adjustment of the shift rods. With the stick in neutral the rods must be adjusted so that the gates in each shift rail are lined up exactly with one another and the stick can move freely sideways from one rail to the other. Adjust the rod(s) by removing the clevis at one end, loosen the jam nut and turn the clevis as required to shorten or lengthen the rod. Trial and error will be required til you get the neutral gate lined up perfectly. If the location of the shifter is not quite where you want it, you could just heat the stick with a torch (a few inches from the bottom so you don't wreck the shift mechanism) and bend the stick over a bit closer , or maybe bend both sticks closer to the drivers side. Just be careful not to start a fire in the cab!!!! My opinion on the air shift is that if this was a work truck and that would make it get the job done better, then maybe it might be worthwhile, but on a classic such as this the stock shifter working properly would be much nicer.

Is it definitely a Roosa Master, or could it be an American Bosch PSJ rotary pump? Never saw a Roosa Master on a Mack engine, but the PSJ kinda resembles a Roosa Master, and was used in that time period.