These are photos of my friends dad's R model dump. The truck is a 1967 Mack R model. It was a 6 wheeler tractor pulling a dump trailer for Stamford Demolition. It originally had a 711 diesel in it, a 20 speed twin stick (aka Quad box) and a 29,500 lb rear end. The truck was stolen and kept in a hanger for a few years. When it was recovered, Stamford House Wrecking did not want it so Bridgeport Mack took it in. My friends father bought the truck in 1977 and put the dump body on. The truck was rolled at one time and that's why the top of the cab is messed up. The truck now has a 237 mack engine in it and still has the quadbox. While it's not pretty, it works every day. He has a mint cab for the truck in his garage, but hasn't put it on the truck yet. Here's the first photo from the rear.
Here's a shot from the front-
Last shot-
THANKS--Brian--I just looked it OVER! & having spent many hours in ONE--brought back some pleasent Memories! -- --Ole JIM--
Here in Fredericton there is a company that has more than a few of these R model macks equiped with dump trailers that haul sand for about 8 months a year then sit in the winter (never see salt), they look to be in great shape. I heard that the oldest was a 1977 and the odometers have cliqued over at least a couple times.
I didn't know that the 711 ever made it to the new style cabs,that is after the "B" models.Ron G
We had many 711's in DM800's back in the day. Which is basically the same cab as the R, except they have the steel front fenders with the "Butterfly hoods". I know where there is a left front fender for a DM 800 that has never been on a truck, just the factory black primer! If someone needed it I could make it disappear! I believe that "20 speed" is actually considered an 18 speed. As I recall there are two gears that you are not suppose to use. I was told once that if you did it would damage something but actually I believe the real story is that two of the gears are duplicates of others so no real reason to use them.
Yair . . . kshansen There was a lot of folk lore about those transmissions, but I believe you are right . . . in fact it was even worse. I have forgotten the details but on some of the trucks that ended up over here on some sequences if you followed logical progression going down through the boxes you could in fact be shifting up . . . disconcerting to say the least. On the triplexes if you ignored third gear in the joey box and just treated it as a bog cog and ran that second lever as a splitter it was a similar deal . . .if you used fifth/low and then changed to fourth/high you were actually shifting up. It is strange how things are different in our countries. I find that little short azzed body on a single drive to be really disconcerting on such a truck. I will stand correcting by some of the Aussie truck blokes but I have never seen one and I think they are almost unheard of over here . . . perhaps down south? Cheers.
That is the reason,two duplicate ratios and I used to know what the were but I'm pretty sure that it was a combination of first in the auxilliary and maybe third in the main because deep under was about equal to to two gears in the main box to maybe 2nd in the main box and high split or third low split to duplicate each other.Mathmatically there were 18 speeds but logically there would have been been 20.I don't recall ever seeing a problem with that transmission and if you greased the shift rails in it it was a nice shifting tranny as well. I drove the DM800 for years but they always had the 673 or the Maxidyne 675 in them.I am pretty sure that the drivers manual had a diagram of the gear ratios in it.Ron G
I would have to say that of all the Quadraplex transmissions we had 90% of the failures I saw were failed reverse idler gears. Most likely operator abused. Most of our trucks were used for stocking trucks in stone quarries and a long haul from loading to dumping would have been 1/2 mile. So in an 8 to 10 hour shift reverse was used a lot more than an over the road truck.