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Also, I typed the Mack P/N into google from the  injection pump and came up with an ENDT676, which would be the 285hp Maxidyne 300. I read that in 1980 the name was changed to EM6-285. I'm guessing that means I've got a pre-1985 285hp Maxidyne because this engine still retains the turbine? I'm not well educated on these things like you guys, but I am here to learn so lay it on. I also cannot find any sort of stamping that would say "ENDT or T676" anywhere on top of the timing cover.

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On 7/11/2020 at 7:00 PM, Red Horse said:

Uh Maddog-ignore my dig on Visors-not intended to include Lunds😎

34149F9D-7466-441A-A62B-2AF18F3A543D_1_201_a.jpeg

holy shit....what a good lookin SOB ......bob

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Nice find on the dump truck!  Welcome aboard.

That 285 will move that down the road easily.  As for shifting?  With that engine, you won't have to worry about splitting gears much.  Just drive it like a 5 spd for the most part when empty.  Just try to keep the RPM's above 1500 or so.  

Even with my 237 hp and Triplex, it will let you know when  you are trying to run it down a bit too much on RPM.  Just have to mind your manners and listen to see if the transmission starts "talking" to you.  The whole issue is these old boxes are SINGLE countershaft and all the newer stuff are double or triple countershaft.  Those will put up with the low end grunt put out by these types of motors due to the fact the power is split up by multiple shafts.  The old Quad box will just spit parts out!


The engine number is on the top/front of the accessory drive casting(in front of the pump and access hole)

Edited by Freightrain

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Larry

1959 B61 Liv'n Large......................

Charter member of the "MACK PACK"

 

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That motor I feel is a fairly early Coolpower as it hasnt got series intercooling, not sure when it changed but early 80's at a guess

The ones of those I have had anything to do with have engine number on the left rear bellow the exhaust manifold 

Oil reservoir looks like one from a Mack so Im guessing it got a whole lot of goodies and things done when the newer motor went in as the power steering pump is on the back of the compressor so it was no doubt a good time to change the front axle 

 

Paul 

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And the Tip turbine or Coolpower as they were called in Australia doesnt make it a Maxidyne, its the rack on the injector pump and the way it provides a flat torque curve that then enables the motor to lug from 2100 to around 1150 RPM without loosing power. I also believe Maxidynes had different stronger blocks with extra webbing cast into them and no doubt hundreds of other small differences but it was the same basic motor 

This meant  you needed only 5 gears to run semi trailers interstate up and down the biggest mountains and pull high heavy loads into head winds all day with out changing gears very much at all

Looking at that last photo I would say that series intercooling became available in Australia in in 1983 so maybe 1982 in the states

Plenty of information on how the Maxidyne works and the principal behind them

Paul 

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  • 2 weeks later...

Running empty or moderately-loaded, I didn't usually "split" the Quadruplex gears.  The 18-speed has 2 overdrive gears, and the 20-speed only has 1.  On the 18, 4th is direct (1:1).  On the 20, 5th is direct.  On the 18, Lo-Split 5th is basically the same ratio as Direct 4th, and Direct 5th is basically the same ratio as Hi-Split 4th.  So, Lo-Split 5th and Direct 5th don't get used, and they don't count those 2 gears.

Typical sequence for the not-too-heavily-loaded 18-speed went kinda like this:

Lo-Split 1st

Lo-Split 2nd

Lo-Split 3rd

Lo-Split 4th

Direct 4th (1:1)

Hi-Split 4th (OD)

Hi-Split 5th (OD) (BIG drop in RPM!)

On the 20-speed, I'd go all the way to 5th in Lo-Split, then Direct 5th and Hi-Split 5th (OD).

The Quad box, like they are all saying, is not really rated for the mid-range torque of the Maxidyne.  But, if it isn't pulling heavy, it will probably be fine.  And, like the man said, keeping the RPMs up in the higher ranges will help, as the Maxis made their peak torque at lower RPMs.  Remember, the transmission is not destroyed by the torque the engine is RATED at, but rather how much torque is actually being APPLIED...right now.  I've pulled some heavy loads behind a Quad, but ever heavy loads AND a Maxidyne.

 

Nice find on the truck.  Lots of helpful folks on this site.  And some of these guys know more about Macks than anybody except the engineers that designed them!  Enjoy your 'Dog!

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"Eagles may soar, but weasels don't get sucked into jet engines."

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This old B Model is an attention getter (lol)  I still wonder if it actually has a Quadraplex in it. In an earlier post the new owner mentioned something about using a pry bar of some sort to cure being stuck in gear ???  I don't see how you could do this with any Quadraplex.  An old 300 and 5 speed back around 1980 ???  wouldn't have been very difficult to find a donor like an F Model or even single axle R back then. I also wonder if after sitting and not having any filtration on the tip fan , if it even still spins....let alone if the intercooler is plugged up with dust.  I'd think in this day and age someone like K & N makes something that would easily work for a tip fan.  That truck also has hydraulic power assist steering.  I thought it was air until seeing the later pictures..... somebody loved that little girl    

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that good lookin SOB might get a heart transplant over the winter. i love the sound of the straight piped 707,711 but the balancer is wobbling too much to my liking, not trying to steal the thread

post-6-0-64947600-1408238925_thumb.jpg

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The Mack compound boxes did have some of the linkage exposed on top of the transmission.  See the link, below.  One of the pics shows the top pretty well.  The linkage from the compound shifter to the rear (compound) box are exposed.  So, yes, someone may have used a pry bar to move linkage if there was a problem with the shift linkage.

 

 

"Eagles may soar, but weasels don't get sucked into jet engines."

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  • 2 weeks later...

Sorry y'all I've been away on other adventures for the past two weeks. Did buy some tires for the ol' Mack and hope to have her rolling down the road real soon. It's for sure the quadruplex like the one above. It got stuck between gears when getting sloppy on shifting. It'd rather you follow the pattern of straight lines rather than diagonally jumping across the gates or using a circular motion to go from low to direct. I got her figured out though. Gonna try and find a big filter for the tip fan, fitting one under the hood is a different story.

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  • 3 months later...
12 hours ago, terry said:

Keep the rpm's up with the quad, they don't like to be lugged, like you can do with that engine.   terry:MackLogo:

So what RPM is to be considered lugging on a 676? What kind of powerband do I need to keep this thing in?

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You can pull that 676 down to about eleven or twelve hundred, thats why they had the extended range six speed trans. but that is a triple counter shaft and will take the torque the 676 puts out at low RPM's, but the 72 series will not take the constant low rpm lugging. the 72 series will be okay behind the 676 just keep the rpms  up around eighteen hundred or more, I had a DM dump with a 237 and a quad box and had no problems for a bunch of years, but I was the only driver, if it is a hobby truck i would not worry at all.    terry:MackLogo:

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12 hours ago, terry said:

You can pull that 676 down to about eleven or twelve hundred, thats why they had the extended range six speed trans. but that is a triple counter shaft and will take the torque the 676 puts out at low RPM's, but the 72 series will not take the constant low rpm lugging. the 72 series will be okay behind the 676 just keep the rpms  up around eighteen hundred or more, I had a DM dump with a 237 and a quad box and had no problems for a bunch of years, but I was the only driver, if it is a hobby truck i would not worry at all.    terry:MackLogo:

Exactly.  Keep the Maxidyne up in the 1800-2100 RPM range, and it is well off its torque peak, which was down around 1200 RPM.

It's only when the RPMs start to fall that the increased torque of the Maxi becomes prevalent. 

And, like Terry said, if it's just a toy, and isn't too heavy, it probably won't be an issue anyway.  But, if you're gonna work it, just keep the RPMs up in the normal Thermodyne operating range, and drive is sensibly, and it should be fine.

That being said, the 676 still is a monster, torque-wise.  Look at the graph below (for a 285 HP version).  Even at 1800 RPM, it's still got 825 ft-lbs on tap.  That was more than most transmissions of the day were rated for.  Hence the triple-countershaft Maxitorques.  I wouldn't jerk it too hard!

I have heard of several folks running a 237 in front of these boxes, and that works very well if you stay out of the fat part of the torque curve.

image.png.e38be8d9bb52ea0865688cc8737c5ef0.png

 

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"Eagles may soar, but weasels don't get sucked into jet engines."

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Got it! My plan is to work this truck when I can. Just bought a spray gun over the weekend and already have half the bed and frame painted, as well as half of the tires changed to newer used ones donated by my friend who works at a Love's Truck Stop. It's taken me longer than I hoped, but doesn't every project? I'm not going for a restoration, just working towards having something presentable if I want to attract a customer base. I'll post some pictures from my cell phone later on tonight. 

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On 7/23/2020 at 1:02 PM, doubleclutchinweasel said:

The Mack compound boxes did have some of the linkage exposed on top of the transmission.  See the link, below.  One of the pics shows the top pretty well.  The linkage from the compound shifter to the rear (compound) box are exposed.  So, yes, someone may have used a pry bar to move linkage if there was a problem with the shift linkage.

 

 

I forgot all about that

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22 minutes ago, Mark T said:

I forgot all about that

I've had to climb under and pry a few times since I've had it. I believe there's a fix that involves welding the stick up on the bottom where it gets worn after years of use and grinding it back to size. If it becomes a regular problem, I'll fix it. 

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