doubleclutchinweasel

Look for numbers stamped anywhere around here. Usually had something like "T 673 C". LOOKS more like an ENDT-673 or ENDT-673C. But, I BELIEVE some of the earliest 675's may have had that cartridge-type "oil clarifier" instead of the spin-on filters. Like they said, VIN number will give a clue as to the original engine. Best place to get the VIN is actually on the RH frame rail, just behind the front shock mount...just barely out of view in your picture.

I'm actually "CDO". It's just like "OCD", except that the letters are in alphabetical order, like they are supposed to be.

If I get a chance to go back down there, I will try to get more information about the truck. Maybe some more pictures, too. It is in a working mulch yard, and they are fairly busy at times. So, I don't want to interfere with them working to look around. Vlad, every Duplex I ever saw had the compound stick on the right. MOST of the Triplex and Quadruplexe boxes I saw had the compound on the left. When he said the compound on this one only had 2 positions, not the 4 on the shift plate, my first thought was that someone may have changed out the box at some time. But, again, if I can get up under it, I might could tell more about it.

I have seen a few with the compound on the right stick. Never paid much attention to them. All the ones I drove had the compound on the left side, and were all double-overdrive 18-speeds. Again, I was not paying enough attention!

I should have checked the VIN. But, he had 2 other Bs and an R there that I was drooling over...

I really think it was probably re-powered. Did not look at it that closely. But, the cab was way more solid than most I have seen. Definitely worth a look if anybody is interested.

Not mine. No association with it. Found this for sale in Morganton, NC. Supposedly has a Cummins engine in it. Shift plate looked like the "reverse quad", with the compound on the right. But, the man said either the box was changed or there was something wonky with the compound (only goes into 2 positions). Cab looks pretty darned solid. I think he was saying something around $7,500. But don't quote me on that! (828)302-0237 or (828)430-9411. Ask for Eric.

That's the world I live in, LTK...the machine shop world. Love it!

Looks like some models went as late as '85. R709 1966-1967 42 R711 1966-1977 226 R711R 1970-1970 30 R715 1965-1970 123 R715R 1970-1970 5 R719 1965-1970 262 R723 1967-1967 4 R731 1966-1973 102 R733 1972-1974 17 R734 1978-1980 41 R735 1977-1977 8 R737 1965-1973 563 R738 1981-1984 40 R739 1969-1971 15 R747 1972-1985 661 R754 1978-1985 314 R761 1970-1974 92 R763 1965-1974 629 R767 1972-1985 2,209 R769 1975-1975 13 R770 1977-1985 136 R773 1967-1978 1,801 R785 1969-1972 44 R785R 1970-1970 60 R795 1970-1979 2,144 R795R 1970-1976 233 R797 1971-1979 641 R797R 1972-1979 300

Chrome plating can cause hydrogen embrittlement. I believe there is another "baking" step that can be taken after plating which mitigates some of the effects. But, it has to be done at a certain temp and within a certain timeframe after plating. If plating is done and the baking process done correctly, there should be no problems. But, if the baking process is skipped or done improperly, you get a brittle part. That is probably why it is frowned upon in certain circles. There is lots of information out there you can search on the matter.

I can't remember. Somebody remind me what the SECOND "R" stands for (Like in the R795R). I know an "F at the end was for "Fire" apparatus. But, I can't remember what the "R" suffix meant. Slippin'... Never mind. Right-hand drive. Duh! Like I said, slippin'! LOL!

Four, in 1968, it appears...

Don't we all...

I'm not sure. I was thinking all the later ones had the pivot mount on the front, regardless of mount type. But, I can't swear to that. Maybe every later model I saw just happened to be air ride! I do have that kind of thing happen to me from time to time!

As I recall, Mack gave the reasons as shrinking market share and lack of profitability from that plant. Even that new plant in Winnsboro, SC, did not last long. There were some tough times going on through those years.

The "Rocket Bird"...

Have frozen many a piece to put into other things. Bearings, bushings, liners, etc. Freezer is great. Used to have a spray called "Minus 96" that we used to chill parts. A heat lamp inside the receiving casting also can help open up the receiving end of the deal. Welding inside the old part definitely helps remove it. Had to pull a 36" bearing race out once. Ran a MIG bead around the inside of it. Once it cooled, it practically fell out. Constantly using temperature differential to make things come apart or go together. Metal moves a LOT when it heats and cools. Just be sure to use enough, so you don't get stuck half-way in! That kinda sucks! These guys are all giving good advice, and on the same specific subject. I would trust them!

This was a R-model schematic. Note the Stop Light Switch and Double Check Valve near the treadle valve. Not sure if this is the same on your newer unti, but it might give you some ideas

There is usually a check valve or a double check valve right there. Attached is some double check info. I don't care much for the push-lock fittings, personally. YRMV. The "plastic" compression stuff is probably DOT air line tubing and fittings. Really good stuff. DC Valves.pdf

You know, now that I think about it, I THINK I jacked up one wheel on a tandem Mack once, put it in gear, and that one tire spun free without trying to move. That truck did NOT have the air locker. So...maybe? Maybe there were full open models? But, I cannot answer that part of the question with 100% confidence. Interesting question, though.

I'll take your word on the Lanova RPM range! I'm just saying that Mack referred to the 673 as a "high speed Thermodyne". Might mean about as much as the "wide track Pontiac" from the '60's...which had the same track width as its Chevy or Olds cousins! LOL!

Biggest snag I remember (US cabs here) was that the "short" pre-'73 used a different type of front cab mount than what you see in the picture. That one is the later "pivot" mount. The older ones had a flat mount with a round rubber biscuit between the cab and mount.

I've been following this one for a while, but have said nothing. It has been fun watching the comments on here. Like on so many of these, there is more discussion happening than just what relates to the original question. Guess that's why I like it here so much! When Mack brought out the "673" series Thermodyne (still 672 cu in), they made a point of differentiating it from the earlier Lanova engines by referring to it as a "high speed" engine. I am guessing the piston, head, and fuel delivery were system were the primary reason for the higher RPM range. In fact, I think Lanova was the name of the combustion chamber design patent those earlier engines used. Really like re-living the old Maxidyne/Maxitorque era! I remember when those first started showing up. Personally, I never got used to the 5- and 6-speed transmissions. Just hated the RPM drop between gears. Too much time behind a Quadruplex, I guess! But, the Maxi engines were definitely revolutionary for their time. Still cool to read the old brochures. Takes me back to when I read them for the first time. That whole Idea of "high torque rise" and "constant HP" was so different from anything else out there. Somebody mentioned earlier about Mack having engineering power back then. Yes! I am an engineer myself now, and can really appreciate what Mack did then, taking a step out of line and doing something so different. Took guts. And, as somebody else already mentioned, I think constantly tightening emission regulations were the downfall of the Maxi setup. Easier to run clean if the engine stays in a more-or-less constant RPM range. Same thing is still happening today, with cars and pickups getting more and more gears. The most efficient, and least polluting engine is one that runs at a constant RPM, right in the "sweet spot". Anyway, just thought I would chime in here with my 2 cents! Hope everybody had a great Christmas and a happy new year.

Yes, R611 was ENDT-673C, 250 HP, and would have had the tall air cleaner. Fuller transmissions were definitely an option, too.