JoeH

If I had the money I'd just buy a mid 90s Rd, drop a new frame in, rebuild engine trans and rears and call it a day. Would still be cheaper than new, and would spend a lot less time at the dealer. But if you're bent on new, I'd agree the dealer makes or breaks the brand.

Engine looks like an ENDT676, rated at about 283 hp. Engine tag should be on the valve cover or near the fuel pump... Likely has a 2 stick transmission: left stick is 1-5, right stuck is reverse, lo, direct.

We had a Jake on our '79 endt676 up until last year when we had to delete it. Weak valve spring on one cylinder wasn't closing fast enough so the disk sitting on top of the valve kept popping out, resulting in that exhaust valve suddenly having way too much valve lash. I ran the truck pretty much every day for 6 years here in southeast PA. The truck shifts gears twice as fast using the Jake. Which means climbing a hill you wind it up to 2100+ and when you shift you're still in your powerband with the perk of still having your turbo spooled up. I've driven the truck over blue mountain a couple times, that's a nice hill. Don't let anyone here dissuade you from a Jake on your Mack. Its completely worth it just for climbing hills alone. And a properly adjusted Jake brake works well on these motors, you just need to ride it around 2100 rpms. When I retire my '79 I'll likely restore it and replace the valve springs and put the Jake back on.

And to add, I have a retired 1980 DM686SX with a 20k steer axle, I would guess 12-16 leaves but I never counted that truck.

My 79 has 3 leaves on an 11k steer axle, just bought an '88 with 4? Leaves on a 20k steer axle, and I have a 95 with a 16 leaf 18k steer axle. The 79 is an R686st 88 is an RD690S 95 is an RD688S It's not really a year thing, it's more of a weight rating thing....

Up until the early 80s the VIN number would be something like my 79's: R686ST30072. This would tell you which engine and typically suspension. ST was a six wheel tractor typically with 38k Camelback, though sometimes 44k S would typically be 44k Camelback SX would indicate extreme cameback ratings of 55k+. Make made 80k rears too, which I think just used a Ridgid beam instead of springs on the Camelback. I wouldn't want to ride that truck....

The 2 valve ENDT676 went away in the early 80s I believe, as the 4 valve heads were phased in. Honestly not sure about the 87 "Econodyne 350hp 686" with 6 gears. To have a 6 speed it must have a hell of a powerband, much like the maxidyne. I know there were Econodyne versions of the 2 valves, I always assumed they had the same big powerband the maxidynes had, just with a few fuel saving tweaks. My numbers are correct on the 685 and 686 up until at least the early 80s; they may have modified their numbering system when they introduced 690 to indicate maxidyne. That would leave the R686 meaningless, perhaps they repurposed the number. This is also around the time when the R became RD I'd guess...

Perhaps; clean your wire connectors and put dielectric grease on the connector?

Your 87 is a maxidyne rated at 300 hp, whereas your 89 was a 350 hp econodyne. Same engine, different fuel pump. The Maxidyne makes 90%+ torque from 1020 rpms to the governor, whereas your Econodyne didn't. The Maxidyne's powerband can't be compared to any other brand's 300hp because no one else has one that has that big of a powerband. You don't need many gears because you're always making peak torque.

68"5" was the 237hp variant of the 672 cu inch 2 valve diesel, 68"6" was the 283 hp variant of the 672 cu inch 2 valve diesel, 68"8" is a non maxidyne engine, commonly rated at 350 hp, designation used both on E6 motors and E7 motors 6"90" was the maxidyne version of the E6 and E7 motors. The E6 uses the same 672 cu inch block as the old endt676 motors of the R685 and R686. Probably minor internal block changes typical over years of running the same engine. The E6 used 4 valves per cylinders, whereas the ENDT675&6 used 2 valves per cylinder. So they have different heads.

Is that ready to go as in you're selling? Or ready to go as in still runs and you use it on your property for fun?

Probably depends how well you can leverage your anger at them.

The power steering pump is really the only crossover point between engine oil and power steering. Rebuilt pump is probably only a couple hundred bucks. I'd go through dealer though, using your vin. My engines all have the PS pump on the back of the air compressor, on the front of the timing cover would turn opposite direction. Not sure if the pumps work right spinning backwards.

New fuel filters, pops was goosing it to clear any air in the system. And for fun. Managed to get a picture of the smoke.

My company is just my dad and I. No one but family has driven our trucks in over 20 years. Don't need some idiot breaking my old trucks because he wants a newer one. He would find himself out of a job real fast with a pretty salty employer reference. You can't beat multi speed reverse transmission for concrete truck work. A 2 stick in 3rd reverse will get me in places the 8LL will die in.

Lol my 2 stick is a `79 and works just about every day. Had 350k miles on it as a tractor when we bought it, we have about 250k miles on it since we got it in '86. We run a 15 mile radius delivering concrete. Lots of short runs in traffic, lights, stops, hills... very few highway miles. Lots of shift cycles. This one isn't a hobby truck, we drive it like a work truck. Shift, floor it. Shift, floor it. Shift, floor it. It has never complained. I'm assuming the Eaton was beat on but I have no idea if it was or not. But the 2 stick survived my brothers and I learning to drive on it right out of high school. Still shifts as good as ever. Up time in the 11 years since I started driving is close to 99%. And you have to factor that 1% downtime can be the mixer`s fault, not the truck. Compare that to anything new.

My Eaton shifts like junk. Someone beat on it before we bought the truck. No thanks, I'd rather a Mack. Though the 2 sticks are the only Mack transmissions I've driven.

I just went to see why my clutch brake wasn't working on my 8LL a couple weeks ago, I had adjusted it a few months before. Stuck my head in and it wasn't there! Somehow the clutch brake broke off and fell out! It gets sandwhiched between the transmission and the throw out bearing on the input shaft.

That's a nice looking truck. Love the paint.

Run the license plate.

Maybe have all 6 made up to ensure they're the same length.

Gears will have dots stamped into their faces where they need to be timed. Take pictures on your way in, print them out and circle timing marks for reassembly reference.

We got our truck used with 385's and put 315's on it because it steered like the Titanic. Tires didn't change anything, so we tweaked the axle stops. I do a lot of 6+ point turns to back into customers driveways. 385's would probably have too much resistance and wear out my steering kinda fast.

Used those in high school in our robotics program, they're not as good as the ferrel type synflex fittings but these are faster to change out the synflex. Push in on the tubing, hold the collar depressed and the synflex should pull out while you depress the collar. To install new synflex your cut has to be square and clean, no burr. Just shove the synflex in then give it a tug to make sure the fitting got a bite. No need to do anything with collar on install.

Why not run 315's?