67RModel

I think there is an ongoing "debate" or discussion as to whether or not the G model was a copy of the Kenworth cab of the time. Supposedly Mack hired Kenworth's designer and the two cabs ended up being mostly identical. (or something like that). The Mack museum even went so far as to research all their records and make a publication about it due to many inquiries on the matter. See below. I think there a few old threads here on the forum about it as well if you search. https://www.macktruckshistoricalmuseum.org/-/media/files/museum/g-model-faq.pdf?rev=9af9c3b4171a46a4944ae8e1caf7e3fa&hash=A661054EBD3DE8B3CBEC5171BC25354B

Might be worth checking with Watts Mack. If they are not available through Mack anymore they might know of an aftermarket source. Honestly your best bet would probably be to just buy an entire rust free cab from a wrecker or junk yard and cut out the panels you need.

https://www.freightwaves.com/news/mack-trucks-fires-back-at-striking-uaws-new-demands/amp interesting article on the subject….

Aren't G models rare or something? And isn't there some controversy as to whether or not they directly copied Kenworth's cab design or something like that? If your looking for one there is one for sale listed on Marketplace in East Greenville, PA. Says they repowered it with an 855 Cummins. No affiliation just passing along the information. https://www.facebook.com/marketplace/item/1137160024337850/?ref=search&referral_code=null&referral_story_type=post

I think Mack engineers knew what they were doing when they designed their engines. There is a reason they have the reputation they do in terms of longevity and fuel economy. If there was a benefit of 500+ HP E7 then one would have been available from the factory. When the E6 and E7s were new a12 liter engine was best suited for the vocational market and linehaul markets where you were hauling legal weights or less, which was Mack's bread and butter. When you send away to the Mack museum for all the literature and documents for a specific truck you will see that each chassis was designed for a specific use case and a maximum speed at a specified grade and GVW as requested by the customer/dealership. From there Mack engineering would select (or recommend) the appropriate engine and gearing to meet those requirements. I think a lot of people asking for more HP out of 300 or 350 Mack engine have other things working against them or are trying to use the truck in a way it wasn't originally specified for. A 6.7 Cummins rated at 350 HP? 😂. The B10 Life for that engine is 250,000 miles. I seriously doubt a 6.7 Cummins under the hood of Mack CH tractor would make one complete trip across the country at 80,000 pounds GVW all else being equal. The power density of the light duty diesels way too high for the type of longevity class 8 engines are expected to get. I think most people (probably everyone) drive entirely too fast. 10-15 over the posted speed limit is basically the new limit. Modern vehicles have got to be so powerful, quite, and smooth that its so easy to unconsciously pick up speed. Modern brakes and suspensions make the extra speed very easy to handle. I think a lot of that carries over to trucking. Guys want to be able to effortlessly fly up big hills and keep up with 4 wheelers.

I'm just now looking at my third picture closely and see that Pete behind my truck had twin stacks. For what? There's only one manifold on his engine. Figure out what that second stack and muffler cost him over his sand career for zero benefit or increase in reliability. Its not a meaningless amount.....

Well lets see it. It started out as day rate. You were paid $2500/day whether you hauled a load or not. This was in the early days when the shale boom was first getting started. The infrastructure was in its infancy and a lot of the pressure pumpers didn't have their $hit together yet. This lasted for about 6-10 months depending on who you were working for and to some extent the well's owner / lease holder. Once it got to true tonnage you were paid down to the hundredth of a ton, so every 20 pounds. So yea....every pound mattered to some. The rate was set depending on the loaded miles from the well to whichever sand yard you were picking up at. Same with the fuel surcharge. Detention was paid at $75/hr after 30 minutes of loaded inactivity. This eventually crept up to 2 hours of loaded inactivity. To some there is. Why leave money on the table if you don't need to? I saw several guys removing their passenger seats, switching to super singles or low pro tires, running 2 batteries instead of 3 or 4 and removing one fuel tank...among many other things depending on the specific truck. They were super committed and willing to go into the weeds and put in the effort for an extra $1500 - $2000 / month. They knew it wouldn't last forever and were only there to extract as much money out of the gig and get out when it wasn't worth it anymore. I don't need a spreadsheet to know if you can cut out even 500 pounds and add that to your net you are going to make more money at zero risk to reliability. At $42/ton, 3 sometimes 4 load per day, 6 days a week it adds up quick. I saw several O/O that got out of heavy haul and into the sand gig. They had heavy tractors to begin with. They went through all the effort to put PTOs and blowers on their trucks but neglected to remove the big chain cabinet from behind their bunk. Like everyone I'm sure they made great money but they also left so much behind. Like I said I never really got into it because I was already pretty light. I worked at night most of the time and hauled overweight. A lot of those sand yards were run by cowboys and would let you leave at whatever weight you wanted to haul. No risk of hitting scales at night. On a few occasions, if the fracking was running super smooth and I was in and out real quick at both ends I would keep 4 or 5 different logbooks with staggered start times and just keep getting while the getting was good. That is all old wives tales and gossip about getting drug around with a dozer in the oilfield. Possibly during the early works of pad construction if your dump trucking in stone. Once a pad is built and and ready for drilling the local roads are modified to take heavy truck traffic and the lease roads are nicer than most local or county owned dirt roads. Zero risk of getting stuck. Like I said before to those guys money is no object. Once a well gets drilled and they start fracking a lease owner can't afford to be messing around with stuck water and sand trucks. At least in Southwestern PA and Eastern Ohio I never saw a lease road that was in any way sketchy or risky to drive on. I don't really know. They must do OK. They are one of the larger dry bulk only carriers in the Midwest and have been in business for over 60 years. They must know a thing or two about specing a truck to maximize ROI for that kind of work. I don't know I lived it for several years and crunched many numbers over that time period. It was always worth it to be as light as possible if you were willing to "do without", go through the trouble to shed unnecessary items or replace items with a lighter equivalent. But you certainly didn't have to in order to make an excellent profit.

I don't know what you mean by this. Its basic math. If you are able to lower your tare weight by X your net will increase by the same X regardless of the pay rate. And yes we were loaded to the last pound plus on every trip. Loaded on a scale under a silo most of the time. Even loading via a conveyor the metering scales on those are pretty accurate. If you told them you wanted 45,000 pounds put on you got extremely close to that. I don't know, the boom cycle of the oilfield is a different animal. The rates were so high money was basically no object. If you wanted to spend stupid money on getting super light you got paid back extremely quickly. I never really engaged in it since I was already pretty light and yes super singles scared me. The guys that did what I described previously about going after every single pound were only there to make money and couldn't care less about looks. I think a lot of them bought trucks specifically for that work and parked their over the road rigs. Sent them to the auction when the bust came. I think the company that had the feather weight Volvos I was talking about did contract pneumatic bulk haul for many different industries/customers. Basically their only business was tonnage so it paid them dividends to be as light as possible since in the non oilfield bulk haul sector the margins are probably razor thin. At the time I kind of admired the way their equipment was spec'd since I knew what I was making and could do the math on how much more they were making with each trip.

The thing about the 12 speeds is they are somewhat scarce and when you do find one they are rather spendy.....at least around here.

Just continue with the plan of running an E6-350 and get a duplex or triplex. Plenty of gears and they should bolt together. Don't lug it and you should be fine. For hobby bobtailing or light loads I would think you would not have any problems. I had a B81 that was repowered with a 237 maxidyne and it still had the 18 speed quad box. It was completely fine for just driving around in......

Does anyone know where Volvo trucks sold in North America are assembled? I have no clue but I would assume someplace here since the ones in Europe and elsewhere globally are so different than the ones sold here. I wonder if any of Volvo's manufacturing here is unionized. I know they make some construction equipment here in the states.....

I thought the all Mack 12 speeds were air shifted for the 10 road gears. The difference being with the compound low could be air shifted with a switch on the dash or a second stick on the floor. Someone else might know better....

To bulk haulers it is. I hauled frac sand for a while. I figured if I could have shaved off 2000 pounds from my tare weight I could have grossed an extra $20,00 - $30,000 per year at the rates then. Some guys got crazy with it. Got lightweight Freightliner FLD120s with series 60 Detroits and flat top sleepers. They would switch the drives out for super singles and run low pro 22.5 steers and then gut every unnecessary piece of anything out of the interior. Some of them even had custom two hopper aluminum pneumatic trailers made instead of the typical 3 hoppers you see. There was a company I ran into that ran a fleet of newer daycab Volvos and slip seated drivers for the nightshift. They had 10 or 11 liter engines, no passenger seats or any interior appointments whatsoever, single drive axle with a pusher and super singles, and ultra lightweight trailers. Their tare weight was a good 6,000 pounds less than the typical owner operator running a sleeper truck with big power. It that game 3 tons more every trip was huge.

Do you still have the Marmon? Is that an aftermarket sleeper on it or a Marmon integral cab? Interesting corner windows on it. I have never seen a such an animal. Did you buy it new? This thread got hijacked. 🤷‍♂️

Geoff do you have any pictures of your fleet from back in the day? Would be interesting to see the old iron.

I agree totally. Spokes for life. It really is kind of sad they have completely disappeared from the market. I personally I think they are safer for on/off road vocational dump truck work since as you said they don't crack. Mack still calls for 240-260 ft*lb on the clamp lug nuts if the stud thread is 3/4"-10 UNC, which is what Mack 44k rears generally have. You can achieve this pretty easily with a 3/4" breaker bar and a small cheater pipe. I have no clue what modern hub pilot lug nuts call for but I imagine its considerable higher than 250 ft*lb? And yes the Budd system is complete diabolical garbage. No question about the advantages of spoke wheels over budd wheels. I can see why the industry moved to hub pilot though. I think no matter how good you get the run out on a spoke wheel balanced my guess is it will never be as good as a hub pilot. Its just the nature of the beast. Some bean counter at the mega carriers figured out there is probably less accelerated tire wear with the hub pilot system as well as considerable weight savings. Not to mention you need to have a certain amount of skill and pride in your work to get Dayton wheels running true....something nobody probably wants to take the time to do anymore. I wonder if you can actually go into a Mack dealer right now and order a highway tractor with spoke hubs? Better yet I would like to see the salesman's face if you did. 😂

Ill have to look at my book later on but the internals are generally different part numbers between the two types of E7s. I'm thinking cam for sure, probably pistons and injectors too. I know even within the Maxidyne family there are differences between different HP ratings. For instance I have a fully mechanical EM7-250 that I want to make into an EM7-300. The cam, pistons, and turbo are the same but the injectors have a different Mack part number and the timing advance is slightly different between the two. You really have to dig into the part numbers and differences. Its not as simple as adding more fuel......

I don't know there is lots of missing information here. Is the speedo accurate? Check it against a GPS phone app. A T2050 has a 0.6:1 overdrive. You would have to have 8.88 gears or something crazy low like that in your rear end(s) to only be doing 43 in 5th gear. Are you getting it into top gear? 5th is all the way over to the right and back against the seat. Is it a tandem or single axle? What is the engine governed at? What are your RPMs when you are maxed out at 43 mph? Yes grinding is most likely operator error. The Mack extended range transmission takes some getting used too and a "reprogramming of your brain" to get the hang of. They are not like other heavy duty transmissions. The steps between gears are comparatively huge.

Like others have said its a 600 series DM of probably 70s or 80s vintage. Can't really tell too much from the single picture provided. You can look on the outside of the passenger side frame rail just behind the front steer tire. Take a wire brush to that area and you will find the model/serial number. Or if the drivers side door tag is still intact it will be there too. My guess is its a DM685S or DM685SX. ENDT675 237hp Maxidyne engine and a 6 speed lo hole transmission. It could also be an ENDT676 with the turbine charge air cooler too. A picture of the engine will easily tell. Tube type rubber. probably 11.00x22 or 12.00x24. Pretty much the best site truck dump truck you can lay your hands on for work around the property/farm. Its a street legal farm tractor. Slow and low on power by todays standards but very reliable. With basic maintenance and upkeep they are almost impossible to kill. It could probably survive a nuclear blast and keep running like nothing happened. 😂

Just wondering what that box is mounted to the dash to the left of the steering wheel if anybody knows.

No an 813 is a turbo Thermodyne if I'm not mistaken. Get in touch with the guy. The deal may possible fall through. You never know.....

No affiliation. Saw listing on Marketplace. Thought I would share here if anyone is interested. Looks like a real nice unit to start a restoration from. Nice original and not rusted out. https://www.facebook.com/marketplace/item/590710523088073/?ref=search&referral_code=null&referral_story_type=post

Yea I thought about this too. I really hate to cut an antique truck up like this that is all original and "modernize" it but I get it. Personally I like to keep things original as possible. I think the slower speeds and lack of creature comforts are part of the nostalgia. For me if I had to get something this nice and original to highway speeds I would just rather trailer it to the location, but I realize that is not possible for everyone.

But your literature shows its a 4 speed. Which is it? Also what is the tachometer say when you are maxed out at 45mph? Is the tach / speedometer accurate? Don't know how big of a pain it would be but you could just go the two speed rear axle route. There has to be a pile of hydraulic brake two speed rear ends laying around from Loadstar and S series Internationals with 20" dayton hubs already installed. A low 5, high 3 ratio split was very common, say like 5.32/3.90. Probably wouldn't be that bad of a job. Would probably have to get a new driveshaft made or yours modified. They yokes probably wouldn't be the same between your shaft and the "new" axle. Keep it in low range and drive it like you normally do and then once in top gear switch the rear end to high range. Pretty simple....

"Hey we are coming up on this real knotty section of this log" "OK lemme grab 9th and let her rip"