doubleclutchinweasel

Clever approach!

The SMART tour (Southern Modified Auto Racing Teams) had a race at nearby Tri-County Speedway last weekend. I took one of the twin grandsons to Richard Childress Racing (RCR) museum earlier that day, and then spent the evening watching the locals and finally the Modifieds run. Here is a picture of the 13-year-old grandson posing with the eventual winner of the Modified race. Anybody recognize the driver? Hint: the driver is the little one!

I see a lot of folks who have been members for a long time, but who have never posted anything (or only a couple of posts). If you are one of those folks, even if you don't think you have anything to talk about, just tell us a good story! Or post a picture of something. You know we all love pictures! If nothing else, tell us who you are and what you are into. We don't care what it is. These guys can talk about almost any topic you can bring up. Tell us about your pets or your grandkids if you don't have anything else to talk about! LOL!

My '70 had the parking brake switch beside the parking brake valve and the service brake switch at the treadle valve.

You nailed it right there! As usual!

Incidentally (and WAY off topic!), isn't it interesting that the newer high-performance racing transmissions are dual-countershaft...ala RoadRanger? This one is a Liberty.

Good point, Geoff. The old "granny gear" boxes in pickups, buses, and medium-duty trucks often had an unsynchronized (sliding mesh) "LO" gear. Many were, as you mentioned, on the "reverse" fork. I drove quite a few of those. Our school buses all had "3-speed plus granny" boxes, but the reverse gear was on a different fork in those. Still probably driven off the 1st gear, though.

I was thinking along those lines. Water is supposed to weigh about 8.33 pounds per gallon (at room temperature of 70° F). If you have access to a scale, weigh it empty and full and see what the difference is. Even allowing for minor differences in the weight of the water (based on actual temperature) and errors in weighing it, it should be pretty easy to tell if it's 500 gallons or 1,000 gallons.

By the way, Gunny, sorry we kind of went off-track there! Didn't mean to hijack your thread! But, it happens sometimes on here! Squirrel! No offense meant to you either, Joe! I actually enjoy these discussions. Nobody around here (work) who can even join in on these kind of things!

https://www.mistertransmission.com/manual-transmission-constant-vs-sliding-mesh/#:~:text=The gears used in a,less wear on the gears More info... It adds the "synchro-mesh" box to the discussion.

E did have a 1-piece also, I think Brocky. Good catch!

"Constant Mesh" simply means that all the gears are constantly meshed. The alternative is a transmission in which gears actually slide in and out of mesh while shifting. Those are called "sliding mesh" boxes. Obviously, neither the Mack transmission in question nor the Muncie of which I posted a picture has gears which slide in and out of mesh while shifting. So, both are "constant mesh" gearboxes. Synchronization is irrelevant in whether or not a transmission has "constant mesh". The car transmission is a "synchronized constant mesh" and the Mack transmission is a "non-synchronized constant mesh". If you want to get super-technical, the "synchronized constant mesh" box can be called a "synchromesh" box, which is basically a contraction. But, make no mistake, these are ALL "constant mesh", by the very definition of the words. The gears ARE meshed...CONSTANTLY. If you choose to call it something else, that's fine with me! Hey, it's a free country! Go for it, my brother!

Interesting observation, FWD!

Kinda like this... This example shows the transmission in 1st gear. Input shaft on left turns counter gear ("cluster gear") on bottom. Cluster gear turns each driven gear on mainshaft. Gears spin free on mainshaft. Inner part of sliding clutches (the "hubs") are splined to mainshaft. When outer part of sliding clutch is moved, it locks into smaller teeth on gear extensions and that gear's rotational speed is transmitted to the mainshaft. The brass "blocking" rings can be seen between the sliding clutch and the gear. The sliding clutch ring, the blocking ring, and the tapered teeth on the gear extension make up a "synchronizer". Notice that the reverse gear is operated by a separate fork, and is not constant mesh. That's why they could grind when going into reverse. Incidentally, this one looks to me like a Muncie. And, from the look of the shallow helix angles, I'd say we're looking at an M22 "Rock Crusher". Strong, but kinda noisy! Yeah, I've had a few (dozen) of these apart!

Again, car transmissions ARE constant mesh. All the gears are meshed, and are turning any time the input shaft is turning. They are NOT tied to the output shaft until you engage a sliding clutch (which is splined to the output shaft) with a gear (which is powered). Then you transmit power. Only primary difference (from a functional standpoint) between a car transmission and a truck transmission is the car transmission uses blocking rings ("synchronizer rings") to match the speed of the gears to the sliding clutch. That's why they start grinding when the blocking rings wear out and no longer have the friction against the cones to synchronize the gear speeds. Lots of the school buses I drove in my youth had worn out synchronizers in them. There were only a couple of us guys who could drive a non-synchro transmission, so we always got those buses! One of them was our activity bus. So, I got to make lots of trips in that one. None of the coaches or teachers could shift it! Benefit of growing up in Macks, I suppose.

So are the car and truck transmissions, just for future reference.

Like Terry said, "685" means ENDT-675 237HP Maxidyne engine. "S" means "6-wheel" (tandem drive axles). "X" means "heavy-spec". Translation: "beast".

The type of clutch you have (Eaton, Mack, etc.) will determine the exact adjustment procedure. Most are fairly simple. That 5-speed has a HUGE step between gears. Upshifting at 1800 will probably drop down to 1200 or so before it meshes up. Downshifting will be about the opposite...pull down to 1200 and then get up to 1800 before slipping into the next gear. You'll get the hang of it. You'll also get the hang of "floating" the gears (shifting without the clutch). Pretty easy. Just feather the throttle to release the load on the gears, slip it into neutral (no effort required), let off or increase throttle to get the RPM right, and slip it into the next gear (again, no effort on the stick). And, like everybody said, only depress the clutch fully to apply the clutch brake while sitting still (otherwise, they can be a PITA to get into gear). No need to push it all the way to the floor if using it to shift.

Yeah, does that say "Hoover" on the nose?

1950-1953, with a few A20s being done in 1954. Here is a picture of one of the more well-known examples.

Could it be an A model?

Hey! I’ve got one of those cards too!

I do hear a lot of folks say they really like them. Tends to make them scarce and expensive.

...bump...

Or find you another Maxidyne to go with that 6-speed. I've seen your work, so there isn't much of a limitation on what you can shoe-horn in there! Comes down to cost and availability. Can't wait to see how it all works out.