We’ve come across some cool old Mack Model B trucks over the years here on BangShift but this one is probably the biggest and nicest one we have found yet. This large and lovely beast is a 1964 Mack B 81. It is a tandem axle tractor, meaning that the rear axle is not driven, it is just there to carry weight, both axles are rated to carry 55,000lbs of load. The transmission in this truck is an 18-speed Mack Quadruplex transmission, known in slang terms as a, “quad-box”. The red paint looks brandy new and the interior is pure, old school Mack perfection. The twin sticks with their cue ball topped shifters, tach that reads in hundreds of RPMs and minimalist gauges, this thing is awesome.
Originally, the truck would have had a 711ci naturally aspirated diesel, but the restorers of this truck went the extra mile and swapped in a 1970s era turbo diesel engine that makes about 250hp. While the big old Thermodyne would be cool for nostalgia’s sake, the truck is far better off and easier to operate with the more modern engine and the 12V electrical system that has also been upgraded.
This truck is proof that it isn’t just Corvettes that look better in red. The big B81 looks dead sexy dripping in red paint. The huge chrome stack and argent on red wheels do no hurt the program either. As you can see by the photos in the ad, it is not simply the top of the truck that is red. Every inch of the frame, axles, etc is also painted red. The cab’s interior is green, which we dig, too.
The B8s were the end of the evolutionary scale for the famous Model B series. In 1966 the Model R trucks came out and the longstanding rounded cabs and bulbous fenders were retired to history. As we have seen in the past, these trucks get good money when sold at auction or on eBay like this one. Tandem axle tractors are more of a rare breed these days. Most of the time we see dump trucks or small single axle tractors, so this big guy is an extra rarity. For $34,000 you can drive it home. Or better yet, you can buy it and hire US to drive it home to you!
eBay Link: 1964 Mack B81 tandem axle tractor
The ad calls it a single axle tractor, but both axles look powered to me. Have to really go through the many photos. One clue is non-powered axles usually have an oil bath hub, but both hubs are the same here. One one shot you can see the rear axle, with an intermediate shaft coming from the forward driven axle. Maybe this one started life as a single axle.
It is DEFINITELY a ‘Twin Screw’, meaning both rear axles are powered. You can see the drive shaft running between them in one of the eBay pictures.
A non-powered rear axle on a tandem is generally called a ‘tag axle’.
This truck was definitely built for off-road use judging by the suspension and gearing (8:1 rear axle gears and a quad-box), and a tag axle has VERY limited traction in an off-road application.
As a former B-model driver all I can say is SWEET! I agree it is a “twin screw”.
Beautiful truck, but.. the exterior was completely restored, the interior was PARTIALLY restored (repaint and re-upholster the interior but leave the rusty gauge bezels?), the engine was probably rebuilt but not repainted. Considering what was done, the $ seems right, it just leaves me scratching my head as to why so much effort was expended on MOST of the truck, when a bit more effort on the ENTIRE truck would have yielded a superior outcome. I’m not talking a concours restoration, just paying attention to the rest of the details.
Still, a beautiful truck.
that is a B model Mack. dad had 2 of them and a Thermodyne maybe 1961 model. and yes that is a twin screw. dad would tune these for a foot of flame out the stack in a hard pull. first Big truck i ever drove