Tri Axle loads and gear ratio

Really nice equipment, too.

These are standard spec, like all the other tractors in their fleet.

 

They'd be Direct drive Transmission..!!

If they had .79OD Transmissions 3.9 Final Drives would give EXACTLY same Revs per Mile..

 

They have the 12 speed Paccar, same as what I have. 12th gear is a .77

 

So you were around one shop and based everything you Speculated on off hear say in that one shop
No after reading your post I quoted .. I fully belive your a driver ..
Your mechanical comprehension I question

 

I’ve had a double-digit number of driving jobs, in nearly 30yrs of driving. Only the tank outfit I drove for had driveline breakage. Their answer was to cut ALL the power out of the trucks. Stuff just doesn’t happen like you claim. If that makes me just a driver to you, so be it.

 

Gotdamnit say it again man. The OP is talking about pulling containers, I pull containers and they're some heavy ##########. Most of the cats pulling containers are local with some regional, no way in hell I'd pull containers with a 2.64 rear and I sure as #### wouldn't buy a used truck with that spec that's pulled containers. You're gonna be paying out the ### for drive line components.

 

I don't run new trucks, but I think a lot of the differences that these newer trucks are very high torque motors. When you have a motor that has an incredible amount of torque it will start you off, I would think,
in a higher gear ratio.

If you look at something like a 671 detroit, it has very low torque so they had like 538 rears or some super low setup and it would pull the weight... slowly, but it would pull the weight without any problems because the lack of torque was made up by a very low gearing.

You can see that as more horsepower and torque came, the rear end ratios were generally higher. May not be exactly accurate, but in the old days 390 rears were probably the choice, now with the newer Motors I'm guessing 355 and 323 is probably the more common types of gear ratios with the higher torque.

The part of this equation that really hasn't changed all that much, is if you look at dump trucks most of them have something like a 464 rear or something that's geared usually in the fours.

That shows you if you're going to be going off road you need to be geared lower.

I think a lot of this stuff when you see those really high rears like that was something that fleets began experimenting with because they were so desperate for fuel mileage. Remember, if a fleet can get an extra half a mile to a gallon that's a really huge deal. As an owner operator, you may be ecstatic to give up half a mile to the gallon if your clutch and Driveline will last you another 10 years. Driveline work is crazy expensive.

Whether or not starting out it is geared too high they could care less because it would give them mileage and they're just going to trade the truck anyway so who cares. It's one reason why they went to automatic so they would stop putting clutches in every other day.

 

336 I could understand but, there's no way I'd pull containers with 264 gears. I've done it and it's a dreadful experience I wouldn't wish on anyone. Those containers coupled with the chassis do not handle the same way as a regular dry van or reefer. I remember pulling a reefer after having spent afew years pulling containers and I had to adjust to how easy they handled in comparison.

 

you need the direct drive trans to go with them, they have different gear sets

any gain from running in direct is off set by useless rears, auto industries have been messing around with this stuff for decades and if they could get their cafe numbers up even a tenth they would have this more common

tire size makes a difference too, no one really runs big rubber any more, 3.90 on 1124.5 or 3.36 on low 22s will be about the same

should be starting off in low gear at all times any way …

Edit: noticed old thread…

 

TALL RUBBAH FTW