What's the difference between transmissions?

different gear ratios for different road/off road applications. As said above, probably the most common transmission for companies are 10 speeds, just for simplicity. I hear 13's are really nice...

 

I don't get why people are using the term "OTR transmission"????? Doesn't make sense.

 

The reason I use the term OTR Tranny is based on the application. Most loads we have on the road gross 80,000lbs or less (truck+load) and the 9 or 10 spd is fine for that. Some guys out there have more specialized situations: 8 axle truck and trailer running 105,500lbs (me); off road goat path stuff like timber hauling or oil fields; lots of mountain running like the Pac NW, etc. The 13 and 18 spds excel in these, so I consider them more a specialized tranny. I had a 10 spd running 105 loads and it stunk; the 13 was far easier. To me the 13 is king when running 70k+ on the highway (MHO).

Sreaming Eagle: I forgot about the 15! Only used it for 2 days in a dump truck almost 4 years ago.

 

Back when I ran in Eastern Canada (lots of short steep hills) we ran tridems and grossed 110,000. 15 sp was real common but got replaced by 13OD pretty much. The guys hauling trains (120 and 125,000 GVW) stuck with 15 and 15OD. They're pretty much gone now. BTW, I learned twin stick 5&4 on my first job.

 

I agree 18 are optimal for heavy haul tractors. But don't you also think they are the best overall choice(especially if you buy your own truck); considering you could use the 18 speed for heavy and shift it like a 10 for normal weight?

 

I was just poking around the Roadranger site, and noticed they never updated the 15 speeds for the higher torque ratings of today engines. 1650 lb-ft is the max rating. I was also surprised to see the 18 actually has a wider ratio spread than the 15. That should have dawned on me considering I knew that the splitter section of an newer 13/18 is underdrive/direct vs direct/overdrive of the older models. Even though they have 2 overdrive ratios, they also are not really a double-overdrive tranny.

To the OP: The 9 and 10 speeds are cheaper, more tolerant of abuse (fewer things to go wrong inside,) and get the job done on-highway with today's broad torque range engines. The 13/18 are available in higher torque ratings for the big motors and offer increased ratio spread, narrower gaps between ratios (~17% vs ~39%,) and increased flexibility in gear choices in the hills. You will have 2 choices of gear in a 9/10 at any given speed, where a 13/18 gives you 4 different gears to work with allowing you to choose power vs. economy going uphill and much greater control of Jake output going down.

 

well phrased, sir.

 

got hollered at for going up a ramp so slow by the driver behind me.18 gears take some time building up but once they are geared up no stoppin em