transmission

The high torque 10 speed weights 602 lbs so not much of a difference! We switched our lowboy tractor from a 9 speed to a 18,what a difference being able to split the gears!! Really nice on the mountains with the jake being able to be in the perfect gear to hold back!

 

Basically an 18 speed is geared almost exactly the same as a 9 speed except you have a half a gear lower in every gear giving you a lower low and a lower reverse.. Your top end or high gear will be the same unless u go back to the older series overdrives.

 

You can convert a 9 SPD to a 13. About 1200. For kits.

There is a thread on it.

. http://www.thetruckersreport.com/truckingindustryforum/showthread.php?t=71506

 

I personally prefer an 18 speed, don't have to split the gears all of the time but when you have too, you can.

 

I'm pulling a stepdeck, got a 10sp, and 435 hp ISX.

Here's the thing, I'll put a couple graphs for you at the bottom here too. Modern engines (at least CAT and Cummins) kind of want to operate between 1100 and 1500, and even better if you can be between 1150 and 1450 or thereabouts. you start going over 1500 you will be burning excess fuel and not getting a lot of pull (torque). And you go to low, well I'm sure you know what that's like, lugging and hard on the engine.

With a 10 sp it seems like you are always going a little beyond what you would like, either running it up to 1600 before shifting, or starting the next gear at 1100. With a 13 the gears are just enough closer together to keep you in the sweet spot.

Some guys like it for hill climbing, my goal has never been to race to the top, I just downshift til I find one that will pull me to the top with ease, but if you want to shift up while climbing a 13 would make that easier.

IMO, there is no need for more than 13 for hauling 80k or less, but as mentioned, if you get a 15 or 18 it will be there if and when you do.

I haul mostly on flat roads and over 1/2 of my loads are light, but I am still insisting on a 13 sp for my next truck if that tells you anything.

 

When an overdrive 10 speed is in 9th gear it's called direct meaning you aren't using the counter shaft gears like in 10th overdrive equating to 30% increase in efficiency in the transmission. You can spec a truck with a 10 speed direct meaning your 10th gear will be direct.