Gear ratio!!!!

Severe duty C500 Kenworth motivated by a Shiny 290. 50mph was dead at the end of what the truck could do, and by that point, the gears were turning so fast that you could smell the transmission getting hot in a hurry. Right around 40mph the truck was comfortable.

 

I don't understand the 18 speeds in trucks that haul 80k or less and are "highway" trucks...

Where I work every truck has an 18 speed, we haul normal flatbed freight, sticks,bricks and steel and we haul bulk, liquid and dry, as well as chemicals in van trailers...

with that said, we go "off-road" very seldom and have no use for an 18 speed, instead we run peterbilts with bottom of the barrel interiors (other than mine, luckily) and im sure most drivers wish they wouldve specd 13 speeds and spent the extra cash on the interiors of the trucks...

 

I hauled dirt with an old cornbinder dump truck that had a 300 cummapart and a spicer straight 7 speed that would barely push 55mph at 2200rpm :X that was kinda crappy for a truck that saw the road...

 

You wanna know how many drivers out there don't know how to drive a 13??

 

Oh, gawd, it won't go back into the low-side!

 

I only took that old C500 up to 50mph once, on a hill, wanted to see what it would do, and, hell, I couldn't get a ticket for speeding unless I kicked it out of gear!

She was screaming before I backed out of it. I'm sure the bearings were getting angry in that box.

 

I would expect that if we had quadboxes or old mack lo hole trannys, but a simple 13 speed? sheesh.

Guess I give some guys too much credit!

 

Did you do any research or just told the Pete guy you wanted to run 75 @ 1300 rpm? I think I would have gotten a Cummins person involved. The Pete guy just wants to sell you a truck. And before you spec out a truck...wheelbase, etc. you might want to get the headrack/trailer builder in the loop. You are spending a lot of dough to not have all parties involved in this. And if that is Cottrell, you need to know that they will tend to use lighter steel in spots on the rails that you can't see. In 1996 we bought 20 new Cottrell quickloaders...11 car flattops. All of them cracked at the stinger on top. The main beam. When the fabricator started cutting out the old beam, lighter steel was inside in spots where it should have been stronger steel.

All I am saying is you just don't go down and buy a tractor and then figure out all the details...you do all your homework before.

 

More "modern" sticks actually didn't need the same sort of gear reduction of decades long gone. As I mentioned, the buddy of mine who runs the 379 with the 3.90/ 5.27 two-speed rears, well, his boss' personal ride is a 1990 W900B Kenworth with a 6x4 set of boxes and 4.56 rears and can start just about as heavy on the side of the mountain (the truck picked up 200,000lbs. gross coming up to Eisenhower). This is with a turned up 444 Cummins. In fact, with a newer set of sticks, 4.11s would have a 100+ mph truck.

I'd have that old C500 in the high side of the transmission halfway through an intersection starting in the low hole. But, it was a fun truck to drive.

Some of the other trucks that have amazingly low gearing you'll find running in the coal fields down in Kentucky and Tennessee, as well as rig-up trucks out in the oilfield. They're 8:1 and higher rear-ratios (although, calculating your "rear-end" ratio is a little more complicated with planetary rear-ends). The guy with the 3.90/ 5.27 379 was telling me about a tandem-tridem bed-truck he delivered at one point, with an 18x4, and 10.29 rear-ends. In the highest gear the truck would top out at 42mph. Of course, the main reason for running an auxilliary in trucks like that is running a power-tower on the auxilliary, allowing you to put the main-box in gear, and control how fast the PTO is operating. You'll start burning up the bearings in the auxilliary if you tried running it in overdrive in both boxes with a set-up like that because of how fast you'll be turning the auxilliary transmission. With those, if you're not running the power-tower, leave the auxilliary in direct and just run the 18-speed. Drop into under or deep-under if you need an amazingly low gear (like skidding a rig).