15 speed direct drive with 2.85 rears slow up hills and poor mileage

I see all this guys going to super high rear ratio in search of 9 and 10 mpg, but it's not for every operation, all those guys claiming high miles per gallon are running very very and I mean very light and bobtail a lot on the same fill up, it is not for every body, I know a guy getting 14 mpg with a FLD 120 with hi rears and a L 10 but he is only moving a travel trailer, yes you can drive slower and not use the A/C to save money but you can only save so much with an 80K# load.

I don't know if that's the case here, but for sure that truck was set for light loads, I had a truck like that but it wouldn't get out of it's own way with a half decent load.

 

Well, that is not quite true. I haul a lot of bulk popcorn, Sioux Bee honey, rolled oats and granola from Richardson milling, Purina and Blue Buffalo pet food, etc that easily tops 45K lb for the load. Many 46K. Sure, I get some lighter loads also. The average weight of all loads is around 37K lb. Add on the 32.5K lb of the tractor full of fuel and trailer, and you can figure the gross.

And my truck with 2.64, being driven by a Series 60 and a Eaton 18 speed, and the lifetime average mpg of the truck at 400,000 miles was 7.93 mpg. And that mpg include staying up north year round. I am quite sure the lifetime average would be higher if I was running I-10 all winter long instead of dealing with winds and sub zero temps all winter, day after day. And I am older, so I love my A/C in the summer months.

And I have no problem walking any hills right along with everyone else. Sometimes even better compared to the fleet spec'd stuff. Sure, it is a slower on the start because of the tall ratio, but running down the road, no problem. I am not concerned that it is slower on the take off. After all, I am driving a truck, not trying to impress babes by "smoking a tire" on a Saturday night out cruising. Several of my loads, I have to work a lot of hilly two lane highways. I am able to do so with no more problem than anyone else.

But I am sure many will fail to be convinced that any of this is true. I really could care less. It works for me, my spreadsheets and my bank account agree, and that is all that matters. Sure, it is not the "ideal' setup for every aspect of trucking that goes on, but for just about every form of general freight, and even refer work, it works just fine. I am not pulling rocks out of a quarry or hauling 300K loads over the rockies, so it is rather disingenuous for some to use extreme circumstances to argue the point.

And, granted, I don't run 70, 75, 80, etc. No need to. My loads are planned and set up so I don't have to. I generally operate in the 62-65 mph range. Nice easy driving. I have no clue how fast the truck will actually run, as it has never been in top gear since I bought it brand new.

 

Oh god are we having this conversation AGAIN!?

10 speed overdrive with 3.55 gears
10 speed direct with 2.64 gears

Both setups start, accelerate, goes up hills, go through the gears, hill start EXACTLY THE SAME!

I'd love to know the ratios of this 15 speed. Can you get the model #?

 

Its not going to make a lot of difference anyways allan. Hes just going to have to get used to climbing hills a little slower because of the bigger gaps in the transmission. I would like to see that emgine run around 1400 minimum at cruising speed myself. Those old trucks without 13/18 speed trans used to spin 1800 rpm for a reason. It was so when they hit a hill the engine kept pulling as the road speed/rpm dropped. Those steep gears kept it in the meat of the power. If he doesn't change anything and the engine is sound he'll just have get used to letting it drop down enough to drop a gear and pull the hill there. Probably be spinning around 1700 one gear down. If hes in hilly terrain he'll wear out his shifting arm

 

16915 no overdrive

 

always in hilly terrain,,I-5 oregon,no cal,,

 

numerically yes,,torque wise-no

 

does great with light loads

 

1994 5EK 14.6L 3406E model Cat

 

You are right! last week I had more lighter loads than normal for the week. So, instead of the average 7.93 the truck has gotten over it's lifetime, It averaged about 9.7 for the entire week, pump to pump hand calculated. Yeah, while the 18 and 2.64 does well overall, it is great when loaded light. No complaints whatsoever.