10 Speed Diagram vs 15 Speed Diagram

Modern truck engines have 400 RPMs of useful powerband. Say 1250 to 1650.

A standard company 10 speed miser would just lumber along at one speed all day hopefully. Its a simple transmission, low 5 and high 5 ranges. Up and down. Nothing fancy.

Now if you had a low range, a direct range and a high range you come up with a 15 speed. Those are relatively rare. My Superliner 500 Mack Dump had one. 15 speeds forward and backwards (Not recommended.) Its not particularly fast but it likes to go uphill because of so many gear steps.

A simple 10 speed going up will drop fast and ur hrr hrr hrr lug down shift you go. And another and another. Until it finally settles somewhere half way down the tree.

A 15 speed can make small shifts down before it settles upgrade.

A 18 speed is for those who understand them. You can pick the perfect ratio in the right gear for any terrain, situation you can think of including the need to stop the planet's rotation in low low. When one of those is put on, think Michigan B train with a gross weight of 160,000 pounds. None of that basic 10 speed crap. You will just snap it off.

Makes sense?

 

When I worked construction we had a Mack CL series with a 15 speed, and a Mack RD series with an 8LL. The best way I can describe a 15 speed is think of it as a 10LL. You can either drive it just like a 10 speed, but in rough terrain or starting out on a steep grade loaded you can use the LL (deep reduction) gears until you have enough momentum to breeze through the normal ranges.
So, with the thumb splitter in low range you'll have 5 gears, and if it's the same concept as the one I drove, the finger splitter will be inoperable until the thumb splitter is moved back to the normal range setting. If that makes any sense

 

No problem, I wish the 15 was a more common trans, it really is good for heavy haul & construction. On that Maxitorque it was a little tough to go from the deep reduction to the normal low range due to the fact that they weren't spaced very far apart. I always ended up starting in 4th on the LL side, then shifting to 1st on the low range side. 5LL and 1L were essentially the same gear

 

If you’re off road a fair amount or do a lot of starting on grades when you’re loaded the 15 would be perfect. Use the deep reduction to get going and then drive it like a 10. I spent almost 10 years in a 15 speed and I liked it for what it was.

 

Yea we did alot of offroading.

One time my foreman in his single axle (The one with the 10 speed and rear axle shifter low high every gear) and my mack 15 we had our boss on top of about 150 foot grass hill above a bridge out situation.

Instead of grinding around the hill up the gravel path we went straight up the grass together stopping nicely at the boss. He did take a step back wondering what we were doing. Nothing much just to see king of the hill game. It was one of those nicer days where a little playtime with tonka trucks were a nice experience.

Now I can imagine any old trucking company in OTR work seeing that outrageous abuse of equiptment going off the road and do stupid stuff. That would call for a thousand firings. However don;t they have companies that already go off the pavement like Swift?

 

Most cases 10 and 15 use the exact same main box (the one you shift with the stick). Only difference is the shift knob and back box. 10 speed uses a 2 speed back box, 15 speed uses a 3 speed back box. Obviously the 15 speed rear box will be a little longer because it has longer countershafts to accomodate the additional gear set and a 2nd air piston for the deep reduction.

The way the ratios stack up, drive a 15 like a 10. The 5 extra gears in the basement are just for a little extra oomph out of the hole. If you started shifting progressively from lowest gear to highest gear, you'd hit 5 gears in deep reduction, shift the back box up into low range and simultaneously shift the main back to 4th. Then you'd hit 5th in low range, then shift the back box to high range and then run thru the 5 gears again. When progressively shifting like described above, you only use 12/15 gears.

 

Great info everyone, I always wondered how they worked. Steel haulers always preferred them,now I know why.

 

God had to invent reduction deep low low before he got the earth moving for the Day and Night in Genesis 1. =) //tease...

 

And an 8LL is the same concept as a 15 speed but on a 9 speed platform.