Burmy

Yes I did know the motor was considered an E6. Thank you for the info on all the other rated HP motors. I am slowly learning more about Mack trucks then intended haha!

It looks like that truck has 56K rears. No leaf springs

I wish I woulda found that truck first ha! If that has a 300 motor, is it a ENDT or a E6. Don't ENDT's only go up to 285hp from factory? I would want to change the tranny on that truck and get rid of the front pizza cutter steers, those tires will sink on most of my jobsites!

Ya that's what I don't want. I was thinking with the 285hp motor, turn it up to 300/ 350, with a 18 speed tranny, 24.5" tires with 4.17 rears I could hit the bottom of the hill with enough speed and momentum and split gears on the way up keeping the rpms higher and not loose to much speed before getting to the top.

I could settle for a 12 speed would love to put a 18 speed in it someday (if it can handle the motor or the 285hp motor down the road)

Is there an 18 speed that can handle this kind of motor? the motor I would love to have in it is a 2 valve 285hp with a large fuel pump to get it up to 300hp - 350 hp. I think I want to stay with the E6 motor just for the old school feel/ sound.... DO YOU THINK ITS WORTH KEEPING IT THEN AND RUNNING IT FOR NOW AND SLOWY FIX IT UP AND REPLACE THINGS AS NEEDED OR DO YOU THINK I SHOULD SEND IT DOWN THE ROAD AND WAIT FOR A DM 886 WITH A 285 MOTOR? WHICH WILL BE MORE IN THE $20k - $25k. yes they are insanely reliable and can take a lot of abuse! which is why I'm a little nervous to send the RD down the road and have this DM take its place, I don't want the DM to be a problem child. Keeping both isn't an option because one will be sitting way to much and become a mouse heaven! and my problem begins!

are the 285's just as reliable the ENDT 676? I'm ok with not quick, I just don't want to be going 10 mph up a hill haha. I totally agree with the no payments!! No payments is way cooler to me then a $100K financed truck!

Ok, I did notice right off the crack the engine idles much lower then our E7 RD

I told that to Joe, that I probably wouldn't of purchased the truck if I knew it was a 235hp and he never responded back.

yes it will be worked hard. off-road and over loaded often! See the picture of our RD, that is what this DM will be doing!

I am starting to see just how pieced together this truck is! It is leaving a very sour taste in my mouth! I do not like the thought of a twin stick they get annoying to run after awhile haha. probably because they are before my time, and I am not good at shifting them !!

How does my 86 DM have a 1974 motor in it ha? I was thinking the 1974 was the emission compliance like it says in the picture below. But then it does say date of mfg. does MFG mean manufactured ?

Trans is a fuller 13 (least what I was told) it looks like I could see eaton cast into the top of the trans. the info plate has been removed from the trans so not sure what type of 13 it is. Probably not the right one judging by all the other miss leading info I have been given on this truck. If I did find a pre 1988 DM the way I wanted which I haven't been able to yet. It would be a $30K - $40K truck probably (350hp motor, 13 or 18 speed, converted hubs to hub piloted, 4.17 rears for better highway speed, pintle hitch with air ran to it, with demo box and multi function gate, and painted black ( we paint all our equipment black ). If I slowly build this one into what I want I will probably still have $20K- $30K into it, but the paint will be fresh the motor and trans will be new. I wouldn't be replacing a lot of this stuff until it goes bad either. But maybe you are right also, that's what I kinda trying to figure out I guess. How quick will the motor shred the trans? 200K miles 50K miles? It will be worked. Overloaded with dirt spilling over the side off road (sometimes in soft soil) is 100% in its future that's why I got a Mack and that's why I wanted a DM. That is what our RD has been doing for years now.

That's what I was thinking when I offered $10K, that I would have some $$$ left over to fix and switch some of these things! and by no means do I plan on doing all these things to this truck over night, I would probably run the motor and trans until they need rebuilds then swap them to what I want instead of rebuilding. It does suck the motor is only 235hp and not 285hp I'm just not sure how it will handle pulling the 20 ton hoe from jobsite to jobsite. First thing will be the rims converted to hub piloted with 24.5 tires if I decide to keep the truck. Then I will probably put 4.17 rears in (just for better highway speed). I am also trying to figure out if the rears in my 94 rd could be switched to the DM. The RD has 4.17's or 4.11 (which I know the 4.11 are not true Mack then, we switched out the rears in our RD 2 years ago and now it does 75mph wrapped out!.

I tried to locate these numbers on the trans, it seems the info plate is missing or is there another place?? Im assuming by how everything else is going with this truck its probably the 12!!

That would be nice however I am yet to get a response from them. Im thinking they are happy this truck is off there hands at this point!

Yes agree, it is weird a lot of the trucks i'v driven don't come with EGT gauge from factory. by big balls do you mean torque? it seemed to get up to speed quick but going up a hill empty it seemed to want to lug down. So i'm just wondering how it will do loaded doing 55mph up a hill. I'm not worried about its capabilities off-road at the jobsite.

Here are some of the forums I have read up on, Only one talks about putting an aftercooler on the ENDT 675. https://www.motortrend.com/news/0707dp-1973-maxidyne-300-series-mack-engine/ http://www.antiquetruckclub.org/forum/?p=post%2Fmack-e6-675-300-two-valve-8181794 ^^^ This guy talks about adding the aftercooler^^^ cgallamore https://www.thedieselgarage.com/threads/237hp-mack-endt673-info-wanted.87742/ https://www.thetruckersreport.com/truckingindustryforum/threads/can-of-worms.36985/ https://www.thedieselgarage.com/threads/350-mack-engine-info.71604/ There was a couple more, but am having a hard time finding them now!

I could settle for 300 HP I think because that's what I currently have and it does the job the (94 RD690s, which has an E7 I believe, the black and red one in the pictures). I also like the model of DM I have which I think only runs up to 1988 maybe 89 then the body style changes a little bit (more sunk in headlights). So I would have to find a DM 686 or 688 under 1988. I am not sure if they even put 300hp in these older Dm's???... Yes the 13 speed was put in later, by Manders which is how they ended up with it, to repair it. Somewhere in that timeframe the original owner decided he didn't want to put anymore time/ money into it. I did bring this up to Joe Mander who was my salesmen, I have not heard back from him yet. They were asking $15,500 for it but it had some many little things wrong with it I offered 10K. Which they excepted, which in todays market seems like a pretty good deal, I was always told you'll never be able to buy a tandem dump truck for less then 15K so I feel like I purchased it at the right price to play with it. I also like to split gears, especially running highway loaded on hills. A lot of these older trucks have the twin stick tranny which I would change out immediately if I ended up with a different truck then this one. From what I have read on other forums the ENDT 675 has the same motor block and stroke as the ENDT 676 and 673. I also read the only difference between the 675 and 676 is the aftercooler and then some fuel adjusting. I will try and round up some of the forums on this. Is buying the aftercooler straight from Mack still an option? I have also read a lot of ppl like the 2 valve compared to the 4 valve that it pulls harder, but that you need to keep an eye on the pyrometer on a 2 valve 🤷‍♂️ Is there any chassis difference between 685, 686, 688 and 690 trucks or is it just the motor & tranny they are built with? I know the S stands for steel frame and SX stands for extreme duty and pry has 55K rear 22K fronts and a walking beam suspension no leaf springs.

A couple weeks ago I purchased a 1986 Mack DM 685S for 10K from Manders in Lakeville. The truck has a 13 speed tranny, and an ENDT 675 motor (235hp). I was told by Manders it had 285hp which would be the ENDT 676. After getting the truck home and power washing the motor block off I discovered it was the 235HP motor (not to happy about it) at the time I did not know to look for the aftercooler and twin pipes to the intake or that DM685 stood for the 235hp motor and DM686 stood for the 285HP motor, I DO NOW THOUGH! I was just going off what the salesman's was telling me! This DM will be replacing our current 1994 RD690s which has 300 HP. The original plan for the DM with "285hp" thought I was getting was to add a bigger fuel pump and make it have 350HP so more then the current RD and then restore the old DM. The DM at least needs 285HP as it will be pulling a 200 series hoe from jobsite to jobsite until we get a lowboy setup. So my questions are now... 1. Can the ENDT 675 handle 350Hp? 2. Where do I find a stock or aftermarket aftercooler? 3. Where do I find a twin tubed cold air intake? 4. Is this motor a 2 valve or 4 valve? which is considered better? 5. Should I sell this truck and try to find a DM686 with ENDT 676 motor? 6. is this the Ecodyne or Maxidyne motor? Which is considered better? 7. How would a ENDT 675 Pair with a 18 speed tranny? over kill is fine 😜 ***Any other thoughts, ideas or concerns are welcomed and thank you for your time and knowledge!*** Other plans for the truck paint it black, covert the bud rims to Hub piloted with Alco or ATX 24" rims. put in 4.17 rears or maybe go 3.94 rears or whatever Mack excepts after 4.17. air to pintle hitch. Hush mats and a better AC system (Any ideas???) remove the pusher axle (better off-road capabilities). Remove all old lights and convert to all LED. get rid of the 20" steering wheel for 16" or 18". Someday a smooth sided box for bigger logo placement with multi functional gate. Also toying with the idea of putting an 18 speed tranny in. I want the low end for hauling equipment and offroad but at least a truck that can do 75mph/ 80mph and not be revved out the entire time. Ultimately this is just a project truck for me, something old and cool to fix up that will be fun to drive, and will be put to work here and there as needed.