doubleclutchinweasel

Don't anybody shoot me if I am wrong, but I THINK there was a tag on one of the valve covers. Or, maybe on the RH side of the head? Also, I think the engine model was stamped on the gear case near the front of the fuel pump. Here is a link to a post I put up years ago. This is where mine was marked "T-673-C". Oh, and VMAC has a good point. By 1985, the 686 probably moved beyond the 283 HP Maxi. He is way more up on that "later" stuff than I am! Most of my knowledge peters out by the early '70s. LOL! And, NO...there was NOT a 17-digit VIN back then. R686ST3147 WAS the number back then. Not sure where VMAC got his number, but he is usually correct on such things. Probably a cross-reference of some sort tha the has access to???

Maybe just a little unnerving working under the cab when it's up...

That "R686ST" on the sticker (if that's the original number) tells you a lot. Like Jojo said, check on the RH frame rail and see if the number matches. I think the 686 uses a 283 HP Maxidyne engine. That information is on here somewhere (wiki?). Normally, there is a plate on the engine that lists HP and valve clearances. Maybe it's 2 plates. The "ST" means it is a Six wheel ("tandem axle") Tractor. Or, at least that is what it started life as.

I assume that one uses the oil feed tube in the end of the compressor crank like all of the ones I have seen. DON'T FORGET THE TUBE!!! It'll make you feel silly if you do!

Did you ever figure out anything on your air compressor???

Look in the driver's side door jamb for something that resembles this...

I am a design and manufacturing engineer, so I tend to look at mechanisms in a slightly different (warped?) way. The twin-countershaft design of the Eaton-Fuller is actually a super good design. The load balances very naturally between those 2 shafts. These were some of the first high-torque capacity transmissions to be developed. And, only having 1 stick was far easier to master than 2. I figure Mack HAD to come up with something to compete with the Fullers on torque capacity. And the original Maxitorque was the result. They had this new Maxi engine, and the old Mack boxes were simply not up to the task of handling the torque. Sure, they could have used Fuller boxes, but...you know! I mean, a RoadRanger behind a 237 Maxidyne was and still is a really nice setup. The Mack triple-countershaft design, if I had to speculate, was probably done just to avoid the patents on the Fullers, or to "one-up" them. If 2 are good, 3 must be better...right? Like I said, I figure Mack HAD to come up with something to compete with the Fullers. And the Maxitorque was the result. The later 13- and 18-speed Mack boxes are a natural evolution of those old original Maxi boxes. Once emission regulations effectively killed off the original "high torque rise" Maxidyne engines, those 5- and 6-speed boxes were kinda short on gears again! So, they took the triple-countershaft design, added the rear section (kinda like Fuller did), and voila! Mack versions of the Fullers! The only "real" advantage I can see for 1 over the other is that the Eaton-Fuller boxes are cheaper to maintain/repair, which, ultimately, might make them more cost-effective (profitable?) to operate. But, that's about it. Like some have said, the gear ratios in the Mack box might suit your operation better. Or, the Eaton might. Depends. I don't think I would arbitrarily remove brand A to put in brand B unless there was some compelling reason. If I had a busted box, and had the other one on-hand, maybe it makes sense. I knew one guy who swapped all his Mack boxes over to RRs just so ALL his trucks would have the same exact box in them. He did it with the clutches, too. Made sense for him. But, if I was driving a Mack box, and was happy with it...damned if I'd pull it out just for the heck of it. On the other hand, if it was causing me grief, out she'd come. Dang! I guess I'm not all that brand-loyal after all! Sorry for the length. Was having a crummy day, and this helped take my mind of of it! Weasel out...

You definitely DON'T need to use every gear every time! In fact, it is extremely rare to need all of them. Just use whatever you need to keep the RPMs where you need them and keep the truck under control. On the old Quadruplex boxes, MOST of the time I only used 7 gears. Sometimes 8. The most I ever used in sequence was 13...or 14 if pulling out of a deep hole. Using too many gears on those 2-stickboxes was a sure way to miss a gear, let your road speed drop, and have to start hunting for a gear that would work! Drove lots of 13-speed RoadRangers, using them like an 8- or 9-speed, and only using the splitter in high gear as an overdrive.

What he said... "M" means Maxi-dog!

What he said. IIRC, the 400 and 500 are the same in mounting dimensions. http://www.bendixvrc.com/itemdisplay.asp?documentid=4384

That is an interesting perspective. I am a Mack guy. But, for my money, it's hard to beat an Eaton-Fuller RoadRanger transmission.

This topic comes up on here all the time. The opinions vary from individual to individual. About the only thing that is generally agreed on is that the Eaton-Fullers are cheaper to repair. There are a LOT more Fullers out there than Macks. Both work. Like anything else, some people have better luck with one than the other. Here's one of many discussions...

Go here and learn all about the 6.0. Not as bad as people claim. But, these guys have a lot of expertise, and can hook you up with some good parts that will remedy most of the issues a 6.0 can have. https://bulletproofdiesel.com/pages/bullet-proof-your-ford-6-liter They can do anything from a full delete, to an upgrade of the factory smog parts to keep it smog legal. I know of several people who have fixed troublesome 6.0s with these guys' pieces, and they run like a champ now. Know of a couple of guys who did the upgrades before they had any issues.

Could that be an actual Mack compressor???

Here's one Mack image...

1. Replace Heli-Coil in existing hole if hole is good. Easiest to try. 2. Instead of Heli-Coil, look into a "Threaded Insert". Takes a larger hole than a Heli-Coil, but can be considerably stronger. There are several different styles. Plain. Loctited. And, staked. I have seen these use a "standard" tap of a larger size for the hole. But, most I have used require a special tap, similar to the way a Heli-Coil tap works. Incidentally, I have seen aluminum (and even steel) parts come from the factory with Heli-Coils already in them.

Should serve you well for many miles!

I sat down in one of those a few years back. The steering shaft angle appears to be different (steeper) than a B61 (flat-back cab). Yes, the wheel hit the stomach sooner, but seemed to miss the knees a little more! I guess you have to decide what body part you want the truck to hurt!

Wow! You even got one in my color! Congratulations, and enjoy!

I like black frames.

I think every B- and R-model any of the local crews had when I was a young'un had black frames. I saw others out on the road that had colored frames. But, to the best of my recollection, all the ones I was around had black frames. Not sure if any of the B's were older than 1960. But, I would suspect at least a couple of them were. Most of the B-model cabs we saw at home were red, yellow, or yellow with black fenders. I don't remember a single one of those having a chrome grille surround. First time I saw one of those I was blown away. Really set the front off. I guess they would sell you whatever you were willing to pay for! Nice thing is, what ever you decide will be great. If you want it body color, do it! If you want it black, do it! The little dog on the hood is what makes the truck anyway!

I have it in my big toes. Don't envy you having it in the knee. Switch to liquor. It isn't quite as bad as beer! Oh, and try to avoid deli meats! Colchicine is for reducing the flare-up. Allopurinol is for ongoing treatment & prevention of flare-ups. It has worked pretty well for me. Take care of yourself, and get better soon.

Agree with everybody. If they are in good shape, and the date code isn't something stupid, they will be fine. It's like I told somebody on here once before; after you leave the tire shop, your "new" tires are now officially "used" tires, too!

Asking about an engine swap will get you as many different answers as there are people who respond! The old mechanical Mack engines should be pretty straightforward. Like the man said, the water pump might have to change to make the length work out. The turbo version of your engine (ENDT-673 variants) would be pretty simple. The 237 Maxidyne (ENDT-675) is awesome. But, as discussed many, many times on here, the Quadruplex (or any of the single-countershaft transmissions) might not be the best bet behind a "high torque rise" Maxi. There are transmissions out there (Mack and others) better suited to the torque curve of a Maxi. And, as they said, there are bigger Maxi's to choose from, too. My '70 had the 250 HP ENDT-673C Thermodyne and an RTF-915 15-speed Fuller RoadRanger. From the build sheet, it appeared there were quite a few parts unique to putting the fuller in a Mack...primarily in the clutch housing and its mounts. That one also had a top-hinged clutch pedal with a cable-operated Spicer 2-disc clutch. So, there were several pages of stuff on the build sheet that were related to putting that trans and clutch in that truck. The '67 R611 I drove when the world was young (and so was I) had that same 250 Thermodyne in it backed by the 18-speed Quadruplex, and used the old "down through the floor" clutch pedal that looked just like the B-models we had back then. As with any project, if you can get all the peripheral parts, or even a donor truck, it will save some hunting for the bits and pieces. Lots of guys on here have done these swaps, and will have far more in-depth knowledge than I do! Good luck on the project!