mrsmackpaul Posted May 20 Share Posted May 20 Whats the difference between a U model and a DN model Mack They both appear to have offset cabs and fiberglass bonnets Is one a lite duty and the other a heavy duty model Im sure the difference is obvious to people in North America, places like Australia never had them at all so it's a little less obvious Paul 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/ Share on other sites More sharing options...
Popular Post Joey Mack Posted May 20 Popular Post Share Posted May 20 I dont know all the in's+out's, but the U's I saw were short nosed and short framed, and set up as tractors.. But I have probably only seen a dozen or so U's.. I drove a small bunch of DM's. They were all tri axle dump trucks.. Thats all I got.. 3 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552115 Share on other sites More sharing options...
Popular Post Mark T Posted May 20 Popular Post Share Posted May 20 Wasn't the DM a different frame ? I think I remeber them being deeper channel from a little behind the cab forward. 2 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552116 Share on other sites More sharing options...
Joey Mack Posted May 20 Share Posted May 20 I bet they were Mark, the ones I drove were quite stout.. of course they were '78 and '79 models... E-6, twin stick, I really like the X-107 transmission.. way better than the replacement 2070... 2 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552117 Share on other sites More sharing options...
Popular Post Brocky Posted May 20 Popular Post Share Posted May 20 Paul I think(??) the DM model designation stood for Dump/Mixer == Heavy Dury work.. The U models were were generally short tractors (prime mover in Aussie) to meet longer trailer length limits. 2 1 Quote Brocky Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552118 Share on other sites More sharing options...
Joey Mack Posted May 20 Share Posted May 20 yep,, Brocky, thanks for reminding me.. they were built offset so that Dump/Mixer driver could see better when backing up. Which was quite a bit of there driving.. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552119 Share on other sites More sharing options...
Popular Post JoeH Posted May 20 Popular Post Share Posted May 20 U models had the same frame as the R600 single frame. DM had a much heavier double frame, with a tall profile from the steering box back behind the cab, and the frame height tapered to "normal" somewhere after the cab and before the rear tandem. I think they were primarily used for concrete barrel mixers and dump trucks. 3 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552127 Share on other sites More sharing options...
JoeH Posted May 20 Share Posted May 20 Largely I would bet the offset cab was to shorten wheelbase for city driving and job site maneuvering. Rather than retool manufacturing for a whole different cab I'll bet they just modified existing tooling to produce the offset and put the drivers feet next to the engine. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552128 Share on other sites More sharing options...
JoeH Posted May 20 Share Posted May 20 We cracked one frame rail vertically on our 79 R600 at the frame splay, and had a 1976 U600 parts truck. Cut each rail (broken and donor) behind the cab, welded them together and put a sister plate (which the truck already had bolted to it) and everything lined up perfect. Spring mounts, steering gear box, shock bracket, etc. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552129 Share on other sites More sharing options...
JoeH Posted May 20 Share Posted May 20 The frame rails on my dm686sx are 3/8 inch thick, both inner and outer. So each side has 3/4 inch total frame thickness. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552131 Share on other sites More sharing options...
mechohaulic Posted May 21 Share Posted May 21 1 hour ago, Brocky said: Paul I think(??) the DM model designation stood for Dump/Mixer == Heavy Dury work.. The U models were were generally short tractors (prime mover in Aussie) to meet longer trailer length limits. correct on the DM designation dumper/ mixer . DM800 replaced the B81 series, DM600 had the two versions- steel/fiberglass nose. the U model (Universal model) was brought in as a B 61 series replacement. U's became a city delivery vehicle sporting lighter frame; shorter wheel bases ; enough to pull longer trailers. the off set cab has been with Mack going back to the LM ? series. as with everything there are exceptions to the rule. a prestress co in CT had DM611st's AND a number of DM611 T's. single axle DM's with 24 in rubber; double rails ;quads; heaviest rear with massive torque arms. osculating 5th wheels on 4in spacers. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552133 Share on other sites More sharing options...
mowerman Posted May 21 Share Posted May 21 You guys about covered it I heard heavier frame, and suspension then the U model … bob and Paul I think they would be really weird with the cab on the other side Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552137 Share on other sites More sharing options...
mrsmackpaul Posted May 21 Author Share Posted May 21 Thank you everyone for the quick response I had no idea what it all meant, I'm still a dumb ass with no idea 🤪🤪 As I read the Dumper Mixer comment by Brocky I got to thinking that U is for universal but was way to caught up with work yo reply So the U and the DM are a different cab, as in more motor is in the U cab than the DM cab ? Great stuff everyone, and as Swishy says, "you can have free pass your very own beer fridge", or something like that Inside a U cab Paul Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552141 Share on other sites More sharing options...
mowerman Posted May 21 Share Posted May 21 I’ve owned both of them and cab size?????? Never heard that bob Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552144 Share on other sites More sharing options...
mrsmackpaul Posted May 21 Author Share Posted May 21 I have no idea at all Im just thinking maybe the U had more engine in the passenger foot well, maybe ? Or maybe not Paul Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552146 Share on other sites More sharing options...
mowerman Posted May 21 Share Posted May 21 It’s possible Paul as I mentioned I have owned both models, but I am certainly not an authority like Mechohaulic says still learning every day, especially on here now I’m gonna throw a monkey wrench in the whole tread. What about the DMM ????? lol Bob Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552148 Share on other sites More sharing options...
Joey Mack Posted May 21 Share Posted May 21 Dump, Mixer, Mining..? Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552150 Share on other sites More sharing options...
mowerman Posted May 21 Share Posted May 21 Maybe you got something there Joey always referring more to cab difference, but I’ll go with that happy TuesdayMaybe you got something there Joey always referring more to cab difference, but I’ll go with that happy Tuesday Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552152 Share on other sites More sharing options...
mowerman Posted May 21 Share Posted May 21 Not sure how that got on there twice double meaning ha ha too early 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552153 Share on other sites More sharing options...
Popular Post Brocky Posted May 21 Popular Post Share Posted May 21 I think(??) the cab and its size are the same, just the frame and suspensions are built for the work the trucks are intended. 2 1 Quote Brocky Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552154 Share on other sites More sharing options...
Joey Mack Posted May 21 Share Posted May 21 Years ago, i had to deliver a repaired DMM back to the quarry. It took over an hour to make the short journey. Top speed was 45 ish.. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552155 Share on other sites More sharing options...
The Heinz Posted May 21 Share Posted May 21 I was just thinking this the other day, glad my question was answered without me having to ask! I thought the question up when remembering passing an old R Model going to work super early in the morning several years ago. I think it was an almost John Deere green, but it was pitch black and I am a bit colorblind. I told one of my coworkers that worked on old Macks previously to being a Cat tech, then to the fleet we both were at, which sparked a conversation about the offset cab models... Man, I love old trucks. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552156 Share on other sites More sharing options...
mowerman Posted May 21 Share Posted May 21 Highcrop and Matt were discussing B model cab possible differences while back got me thinking,,,extra floor braces??? , I guess it’s possible such as convertible cars used to come with a heavier frame ,, remember??? Bob Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552158 Share on other sites More sharing options...
JoeH Posted May 21 Share Posted May 21 Cabs are the same on U and DM. However, the R/U/DM cab started out early as a "flat back" cab, then they updated the cab to a "+3 inch" back wall. They added 3 inches to the back wall to allow more seat room. Not sure how long the U model was I'm production, don't know which backwall our U had, i gave the cab off to someone on here some years ago. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552159 Share on other sites More sharing options...
mowerman Posted May 21 Share Posted May 21 I have a 66 DM also owned an 87U model. I had the same flat back. I understand they were still using them lotta years after they went to the +3. Not sure what the reason for that was I think they gave people an option on the DM and U model I am only 5-7 and my seat is all the way back in the DM I don’t even know how tall guys fit in them Quote Link to comment https://www.bigmacktrucks.com/topic/74171-u-and-dm/#findComment-552160 Share on other sites More sharing options...
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