PITTSBURGH, Penn. - It wasn't my first truck, but the flat nosed Diamond Reo I drove in the late '70s sure had the easiest shifting transmission I've had before or since. In those days 10 speeds were ...
PITTSBURGH, Penn. – It wasn’t my first truck, but the flat nosed Diamond Reo I drove in the late ’70s sure had the easiest shifting transmission I’ve had before or since. In those days 10 speeds were the norm and Road Ranger had a real corner on the fleet market. It was an old truck and the tranny was well broken in when I got the truck, hauling for a regional carrier in the northeast US. I had been hauling cars out of Detroit before that and those old parking lots were so underpowered a hand had to be quick on the draw to stay motivated on a one per center, which was fine in Ohio but got to be work when you hit the Keystone and the one per centers grew into six.
As I recall that Diamond Reo had a 290 Cummins in it and in those days that was pretty much a big horse. I didn’t know much different anyway, and just tried to learn my trade going up and down through the gears, keeping it wound up pretty tight where the torque and horsepower was back then. Point is, that transmission forgave a lot of sins. It was real loosey goosey, which was good for learning. But later on, when I earned other trucks and horsepower rose and split gear transmissions came out, the learning curve kind of stalled and I had to understand all over again.
Horsepower has always migrated up and lately it has gone to 600 and over with the new Cat, Cummins ISX and Volvo’s D16. Transmissions were always pretty much stuck with the 10 speeds until the late ’80s and early ’90s when manufacturers started adding splitters. You’ve got nearly every number of gears now up to 18 depending on your philosophy of what’s necessary to do the job right or maybe just to keep you happy playing with your buttons and knobs.
There are those who will tell you all a big truck needs is seven gears. But you can bog down in the low gears trying to get started with fewer gears and pulling grades can get awful boring when you’ve got seven big gears instead of smaller steps that can keep your speed up. Most guys who love to drive and own their equipment want plenty of flexibility in gear selection and don’t want to worry about getting started or pulling onto an exit ramp up hill and finding a tough turn at the top with a grossed out wagon. They want those splits to keep the truck moving and not torque their tires or their frame. You can keep your shifting smooth and save your expensive equipment with more gears.
That old Diamond Reo tried real hard most of the time but once in a while even the 10-speed wasn’t enough. I remember pulling 25 tonnes of lard for Mickey D’s out of Rhode Island over to Poughkeepsie and getting half way up a hill pretty close to the delivery and grabbing gears all the way down to first and then just sitting there and bouncing. Finally had to back down and find another road. But you’ve got to have an 18 to get those extra gears at the bottom. I could have used another 100 horses, too.
Of course at the other end when you’re running free and everything is whirring like it should on a nice flat super slab, those top splits can be a burden. Some guys think they can run in eighteenth all day on the flat and save fuel. But that last gear is awful big and heavy and it takes a lot of fuel to move it.
If you have spec’d your truck right you can keep it in direct and save fuel and keep those gears for the bottom where they’re useful. I have a friend with a W9 who spec’d his truck with a C-15 an 18-speed and 3:08 final ratio.
He wanted eight wheel lock-up and was told that was as tall as he could go and get all his drives in power. He’s got a power divider for front to back and a diff lock for side to side. Quite a setup. He tells me he’s getting 5.9 mpg with the 3:08 and it pulls well. He can also do well over 125 miles an hour. That’s a large car.
If you are getting almost six mpg pulling plenty of weight on varied terrain, you’re doing something right. You can get more and fleet trucks are set up to get more. But if you want a big horse and you want to get where you’re going the way you want to get there, you sacrifice a little fuel.
You don’t need to compete with fleet trucks. That’s not why you own your own. So your tranny and engine need to be spec’d right for you. Fleet specs are for fleets.
You can run your truck like a business but it’s your truck and there’s no sense being in business if you don’t get some pleasure out of your machine.
Besides power and more gears the big change in putting horsepower to the ground is a torque band that is very broad. You can lug modern engines down pretty close to 1,100 RPM without worrying you’re damaging the engine and there’s more grunt down there. Keeping modern engines wound up wastes fuel. Besides that, the torque is in the middle of the RPM range, not on the high end which means performance has moved down the RPM range into the high middle right down through the sweet spot to the low end.
Now that some engines developed in Europe are coming to North America, there may come a time when the European synchro mesh trannies will come along with them. I have driven European trucks and the transmissions perform exceptionally well especially when gear selection becomes the issue. North American truck drivers are hide bound stubborn about their crash boxes, I suppose because they can shift without the clutch, a much more difficult proposition with synchros. But they may just be the next big technological change in trannies unless somebody comes up with a green transmission with the capability of capturing its heat energy and turning it into power.