HK Trucking

The ENDT 675 is a Maxidyne engine, used with a 5 or 6 speed transmission. The ENDT 673 is a Thermodyne engine, Depending on whether it's an A, B, or C, it could be 205 HP, 225 HP, or 250 HP. The ENDT 673 operating range is 1500 - 2100 RPM, they were usually backed by a Duplex, Triplex or Quadruplex transmission to provide close enough gear ratios to allow the engine to stay in it's operating range.

Actually, the operating range of the 237 (ENDT675) is 1200 - 2100 RPM. Lugging it at 900 - 1100 RPM as you suggest would lead to it's early demise. Torque rating of the 237 is 906 ft. lbs. Putting an intercooler on it will not help much unless you also uprate the fuel system to ENDT676 specs (285 HP, 1080 ft. lbs.) .

Yup, you're right Mike, he's buying her something special. Here it is: http://cgi.ebay.com/ebaymotors/VINTAGE-1973-MACK-RL-700-DUMP-TRUCK-PARTS-OR-COULD-RUN_W0QQcmdZViewItemQQhashZitem4149efeee0QQitemZ280413335264QQptZCommercialQ5fTrucks

Welcome to the board from another resident of the Refrigerated Republik Of Wisconsin.

Well Rob, there's the dump box you were thinking about, plus a whole 'nother truck and spare 866 come with it! .

All the 1974 DM's that I've encountered were a 12 volt positive ground system, are you sure it's 24 volts, or are you just assuming that because it has (4) 6 volt batteries? Never seen a 74 with a series parallel switch. Changing polarity will not make the starter turn backwards, however the heater blower motor will turn backwards unless you reverse the connections to it. If you've got the old type alternator with the floating ground you can just reverse the connections on that too (ground the negative and connect the hot wire to the alt. positive terminal. The voltmeter and temp gauges will have to be replaced with units designed for neg. ground. A 74 would have air operated wipers, so the wipers are not an issue. .

The reason you didn't see that transmission listed on the OldMacks site is that a Roadranger is not a Mack transmission, it is a Fuller transmission (now known as Eaton Fuller). Yes, it's possible the truck was built with a Fuller transmission if someone spec'd it that way. .

If it's only running 2000 RPM then something still ain't right.

Hi Mike. My opinion is that a good name brand oil that meets all the specs required for a particular engine already has all the necessary detergents & additives in it, and nothing else need be added. I always ran Shell Rotella 15w40 in my Mack engines, never added anything. Shell Rotella is the best diesel engine oil out there, in my opinion. At the company where I work now we use Citgo 15w40 in all the diesel engines, we don't ever add anything to that either. Actually, adding things to an engine oil indiscriminately can possibly result in "chemical warfare" between the ingredients of the engine oil and the ingredients of the additive. .

The photo above is graphic proof that some things are just better off left alone. .

Did you check the linkage from the accelerator pedal to the pump? Make sure it's pulling the throttle shaft all the way against the high speed stop screw when the pedal is floored. If the linkage isn't moving the throttle shaft all the way against the high speed stop, then adjusting the high speed stop screw will accomplish nothing. .

Yes. Sometimes you have to get them pretty tight if they leak like that.

80w90 is OK for a 12 speed. Change that air filter if you haven't already, if that doesn't help, then it could be O rings in the shift cylinders, or maybe a problem with the selectair valve on the shifter. Maybe Rob will comment here, as I know he had to rebuid one of his selectair valves .

The weather is getting colder, you didn't by any chance change your trans oil and refill it with a heavier grade, did you? Other than that, have you changed that spin on air filter on the back of the transmission? Sometimes cold weather will shrink the O rings in the shift cylinders causing air to bypass the piston and cause slow or no shifting.

With the old type inner & outer nuts.

I'm sure Watts Mack could ship you a set of injectors. .

Yup, seems to be working on my end now. Thanks Barry. .

It appears to me that it's a 38,000 lb Mack axle with old type Budd wheels on it. .

If I remember correctly Mack started using the spin on filters around 1971. Actually I agree with what Mike said, just leave your engine the way it is, those cartridge filters aren't that bad to change, and if you're not running your truck all that much you won't be changing it that often anyway.

Hey Barry, If I go here: http://www.bigmacktrucks.com/index.php?app=garage&do=view&tab=images&id=251 I can't see any pics. The message says "Sorry but there are no results to display." Sure would like to see that B813SX, but all I get is a blank screen. Same thing with all the other vehicles in there. .

Yes, there could be air pressure pushing the oil past the front seal, or the front seal may simply be worn out or damaged allowing oil to leak out without an internal air leak. You say you just installed that transmission, did you replace the input shaft seal before installing the trans? Also check the breather on top of the transmission to make sure it isn't plugged up. A plugged breather could allow pressure to build up inside the trans when it gets hot, forcing oil out. .

From what I can see, the pitman arm on the steering looks like a "DM 600" type setup. Possibly a later model DM chassis with the LJSWX cab & nose transplanted onto it. Maybe there was a typo in the "LK2DM designation, and the owner was referring to it as a "LJ2DM", in other words an LJ "to" a DM. I still think it looks pretty, no matter what kind of combination it is, and the builder deserves congrats on a job well done. (edit) I just looked closer, and the radiator has the higher top tank, like the 1963 and later B81 had, instead of the top tank that was flush with the hood, as was original on the LJSWX and the earlier B81. .

Wouldn't hurt to put new bearings into it. But if the balancer is indeed defective, the problem will still be there. Swapping another balancer onto an ENDT 676 / EM6 300 is easy, just remove the 6 retaining bolts and pry it off the hub, stick the new one on, replace the bolts and tighten them. The pulley is behind the balancer on those engines, so no belts need to be disturbed. .

The best way is to borrow a known good harmonic balancer from another engine, put it on your engine, then go for a test drive and see if the problem has gone away. Under a no load condition you may feel a vibration at the critical RPM, but with a load on the engine it is more pronounced. .

For the 5 speed TRXL1078: 1st - 8.59 2nd - 4.99 3rd - 2.84 4th - 1.66 5th - 1.00 .