doubleclutchinweasel

Old belts can definitely cause "flutter". So can off-center, bent or unevenly-worn pulleys (sheaves).

Looks like the 15-speed "Direct in 5th" Triplex. Love your truck, man.

"V", correct me if I am wrong, but aren't the primary and secondary needles connected to 2 different tanks? If so, that might make it easier to isolate the system with the leak.

I completely understand! Maybe nobody else would have known it was there, but it would have driven me crazy too!

I think they are super cool. Used to be a guy on here with one. Like the man said, "PICTURES"! We like pictures.

It amazes me the information guys like Jojo and vmac3 have stashed away in their heads. I always learn something new when I get on here. Freakin' encyclopedias!

You know, the front of that thing still reminds me of an Econoline van on steroids.

Not sure if the later models shared any of these part numbers. Cab Breakdown.pdf

I see one around here every now and then. Never can seem to get a picture. May have to chase it down next time I see it!

You know, I don't think I ever saw one of those in person before. Says here they only made 215 W71's from 1953-1958. I'd say that makes it pretty rare.

The Watts guys might be a good place to start. https://www.wattstruckcenter.com/store/

You said a mouthful! Double-clutching a gasser takes a little more practice than a diesel. I suspect it has to do with the rate at which the revs rise and fall. Passes by the sweet spot a little quicker.

Anybody got a picture of an "exhaust turbocharger conveyor" system in-use? That's a new one on me.

Just remembered something while reading all the Detroit comments... Once operated a small tug boat. Had a 6-71 Detroit in it. Was labeled as "Gray Marine". I can't remember if Gray actually built those engines based on Detroit's design, or if they started with the Jimmy and converted it to marine use. Whatever. It was definitely a 6-71 design. The guys I worked with bought me a cap with gold braids on the bill, and for a while I acquired the nickname "Cap'n". The superintendent told me they would provide a life jacket in case i fell off the boat, but would not supply a parachute if i jumped off. Luckily, never had to do either.

My '70 had the inverted camelback springs. Fairly light spec...34K I think. It always amazes me how the guys on here can spot so many details looking at a picture! Serious knowledge housed in the members of this forum!

I think you could safely say that!

Fractured rod joints are awesome. Perfect fit and incredible stability.

Sorry. Had to step out for a while. I was thinking it was sometime in the 80s when the 17 digit numbers came out, but wasn’t sure exactly when. On my ‘70, the title had the vin listed as R611ST5525. It had no 17 digit number. Maybe vmac can confirm this, but it looks like, on the truck in this discussion, they HAD the 17 digit number, but just listed the last 4 digits on the door plate.

Looks like the right info...

By the way, I don't know if the Mack museum is back to normal yet, but they are the best source for how the truck was originally built. Here is the front page off the build sheet they sent me for my old truck.

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???