Mark T

A 15 over is a highway transmission. Couple lower than a ten, and at the time a realistic overgear to make in a lever shift. If you were geared between 3.5 and 4.3 usually 1 2 3 and four in deep reduction, you could go to 4th in regular low range. A direct 15 was quite a bit lower than an RTO 13 and made sense if you had a faster geared truck back then.

Lots of overgear in that transmission

No doubt. I think it's cool seeing some of these upgrades and referbs guys are doing now. Lots of them have been done in the past, but now things that are available that didn't exist years back ??? new twist on things. I think it's interesting.

300 4.17s and a 15 over ??? they work. Lug'n mid 70 some thousand pounds.... they work. 15 has more overgear than an old RTO 13 and in direct with 4.10s still would go in the low 60s.

Still easy to get stuff now to get fresh air to the tip fan without the Mack air cleaner. Duct it from somewhere that was never thought about years ago without spending days making stuff.

There's so much more available now for filters. Geeze, if you have 4.10s ? an old 15 over (like an RTO12515) would be a great choice. a hair more overgear than the Triplex

3.55s with the Triplex ? that's pretty fast even with 20 inch rubber. If I'm not mistaken the Triplex has a little tiny overgear. So even of you didn't cruise in overdrive, 3.55s are still pretty fast in direct (I'd guess well into the 70s)

I would think in 2025 it wouldn't be very difficult to fit some form of K & N filter or something like that on the tip fan and duct it out from under the hood somehow. An air cleaner for the engine wouldn't need to be much bigger than an old oil bath or something as far as real estate in the aircleaner area. They make a lot more stuff now after the diesel pickup craze than back when this was a more popular swap.

Nice Superliner. Can't help but wonder if that'll spark some interest with Spencer ???? They seem to have a knack for locating hiden gems, and I like the idea of them getting into Macks. Not out of the question to see one of those bunks show up for sale some place or on here from time to time.

Ahhhh..... memories of ol uncle bosie. Those zany cannibals alway up to some kinda mischief.

One of the problems with the smaller Mack Triplex or Quadraplex with biger engine was keeping tho oil cool. Once they spent more time in overdrive, oil temp. got to being an issue. If you have a Triplex and a four way behind it ??? you're double overdrive. That bigger engine, likely you'll need a faster axle, and skip the four way. Unless I'm reading wrong

Creeps up on ya, but you realize it all at some point.

Wonder if everyone realizes you need to click on the picture to see them all. Took me a few seconds to remember Other Dog posting pictures like that.

When I was around 20, I used to get stuck doing all that. Got that I could cut motor mounts out and usually not burn anything. Lot's of wet rags.... then you'd get to crawl under and lay in all that (lol) At the time ??? I didn't know any better. I swapped a Fuller 9 speed in one of my CHs one night (no clutch) in 5 hours. It was a reman that had an issue with the synchro. Started when it got in @4 and was test driving @ 9. I ain't got it in me anymore. The CHs were a piece of cake after fight'n old Rs in the past.

Eh....he was happy (lol) My own, I had everything ( I was aware of) in stock. Flywheel, cluthch kit for the Fullers, OTC jack.

Here's a handy little thing I welded up from a grade 8 half inch bolt and an old push in typ adjuster. Bolt it on the cover in place of the push in adjuster and then you can use something 3/4" to get the ring moving sometimes when they're putting up a fight. Sometimes it works, sometimes it's time for a new clutch.

Did an R Model in 6 hours once. Guy was a cheapskate. Just replaced the clutch.

Lots of wet rags too 😂

No rear main. Flywheel in stock already resurfaced.

Think you could still do a dump truck in under 8 hours ? I don't believe I could pull it off anymore. Used to be the norm.

The valve doesn't have to open a lot, just bump it off the seat. It's the overcoming the cylinder pressure is the hard part. Open the lash on a 680 or 346 . Go about .100. be wowed about a week (lol) then watch stuff break like housings or solenoids turned to junk

They could do a lot of things to make stuff work better. Problem is most manufacturers have this thing called a board of directors. They don't really care about anything but how much they can make off of the product. Engineering can only produce what budget allows. Stuff did get better as time went on though. Not many guys can complain about performance of a Powerleash. Then there's the lack of maintainance. I rember the 690 had 6 bolts that held them on to the rocker pedestals. If you read the Jacobs literature, they recomended changing them every 300,000 miles. Not many did, then wonder why they had issues with alignment and oil leaks. Or guys would continue driving the truck with the soft plugs out of the rocker shafts until the shafts were actually gouged out and never be able to keep oil in them like was needed. We're spoiled now with these newer engine brakes that exceed 400 horse of retarding power with relatively little maintainance.

I never understood that. The 680s had lots of oil pressure issues on the top.....and some didn't. I don't remember 690 on the E Techs being like that.

The 690 poked the pin through the adjustment on one valve. 690s had power

The 690 has the pin through the bridge. 680s have the legs that hit the bridge