Horsepower/tranny combination

[Midnight Flyer]

Was browsing Truck Paper.com and got to wondering: what is a good horsepower/tranny combination for just general purposes and optimum fuel mileage? Would 500 HP and a 13-speed with a 3:37 rear be okay for general hauling or maybe 475 HP with a 18-speed? If special ordering a truck what are some combos that would work considering maybe five or six loads a year in the mountains of the western states? 8)

[jegzus]

475hp with a 13spd and 3.37-3.55 gears would be a good general purpose combo, at least from what I have seen. My uncle owns a few car haulers and that is the setup he uses in his pete 379's.

[Jackrabbit379]

475hp with a 13spd and 3.37-3.55 gears would be a good general purpose combo, at least from what I have seen.

Yeah, either the 13 or 18. I've always liked 15 over, too.

At work, we have 350 come aparts, Straight 10(Meritor). Not sure about the rears, but they have the motors governed down to 68. Fuel milage averages around 4.5 - 6.0 mpg. Sometimes, when pulling a single, it gets more around 7 or so mpg. What's funny, my buddy has a 550 CAT in his 379, with an 18 speed. He gets around 5.5 - 6.0 mpg.

[Midnight Flyer]

[What's funny, my buddy has a 550 CAT in his 379, with an 18 speed. He gets around 5.5 - 6.0 mpg.

8) So maybe the folks at Cat are improving the fuel mileage in their engines? From what I've read that setup your buddy has is about ideal for the Cats as it seems the more horsepower engines with 18-speeds and lower rears (3:37-3:55) is about the peak for fuel economy. 8)

[Jackrabbit379]

Yeah.
As long as you can get the right transmission, rears, you can get as good or better fuel economy with bigger motors. Just because you have a motor that runs like a scalded ape, doesnt mean bad fuel milage. :P

[jegzus]

[What's funny, my buddy has a 550 CAT in his 379, with an 18 speed. He gets around 5.5 - 6.0 mpg.

8) So maybe the folks at Cat are improving the fuel mileage in their engines? From what I've read that setup your buddy has is about ideal for the Cats as it seems the more horsepower engines with 18-speeds and lower rears (3:37-3:55) is about the peak for fuel economy. 8)

Well it has more to do with how you drive them and not "as" much as how you set them up. When you put an 18spd tranny on anything it will get good fuel mileage as the rpms stay low while making the power.

Oh and just a heads up the lower the number for rear end ratio's the taller the gear. A 4.11 gear is much "lower" and will produce much more pulling power than a 3.55 but it's top speed will be reduced greatly compared to the 3.55.

[Roadhog]

You don't need an 18-speed. Much heavier Tranny.
10...or 13-speed is all you need.

Those 18's are for Heavy Hauler's, or Livestock, off road applications, etc.
They only help you in lower speeds, and stiff terrain, triple-drives...what-not.

I just delivered a load of Drive axle-housings to Arvin Meritor in Heath, Oh.

Ohhh Baby... :P That new gear smell....

[ssoutlaw]

475hp with a 13spd and 3.37-3.55 gears would be a good general purpose combo, at least from what I have seen.

Yeah, either the 13 or 18. I've always liked 15 over, too.

At work, we have 350 come aparts, Straight 10(Meritor). Not sure about the rears, but they have the motors governed down to 68. Fuel milage averages around 4.5 - 6.0 mpg. Sometimes, when pulling a single, it gets more around 7 or so mpg. What's funny, my buddy has a 550 CAT in his 379, with an 18 speed. He gets around 5.5 - 6.0 mpg.

I dont even think they make a 15 for hwy trucks anymore sense the 18 is doing so well!!

[PackRatTDI]

475hp with a 13spd and 3.37-3.55 gears would be a good general purpose combo, at least from what I have seen.

Yeah, either the 13 or 18. I've always liked 15 over, too.

At work, we have 350 come aparts, Straight 10(Meritor). Not sure about the rears, but they have the motors governed down to 68. Fuel milage averages around 4.5 - 6.0 mpg. Sometimes, when pulling a single, it gets more around 7 or so mpg. What's funny, my buddy has a 550 CAT in his 379, with an 18 speed. He gets around 5.5 - 6.0 mpg.

I dont even think they make a 15 for hwy trucks anymore sense the 18 is doing so well!!

Eaton still lists the 15 speed transmissions in it's sales literature section so I would assume you can still order one. The problem is that it's only rated to 1650 lb/ft of torque so if you're in the market for a big HP engine with 1750lb/ft or torque or better, the 15 speed isn't an option.

[Mack2]

275HP Mack and a 7spd.

[Midnight Flyer]

[Eaton still lists the 15 speed transmissions in it's sales literature section so I would assume you can still order one. The problem is that it's only rated to 1650 lb/ft of torque so if you're in the market for a big HP engine with 1750lb/ft or torque or better, the 15 speed isn't an option.

So does that mean if someone wanted to order a Pete 389 with a 625 HP Cat and a straight ten-speed it wouldn't be available and instead would have to go to an 18-speed? 8)

[Roadhog]

I like that new 389 too!
The bunk is sweet, in the 70" Ultracab. They got smart by putting four latching bins above the bunk...one on each side, and two on the rear bulkhead....and the fridge is placed high over the closet! They also put two swiveling reading lamps...instead of the usual one...so you can lay on either side to read...and not have a head shadow.

...:? I still don't know why you want an 18 speed? (whatta u haulin')
I'm using a 10 now with that ISX Cummins 600. (Pete 387)
Your differential gearing and tire size will also count on how she pulls.
I do like the 13 speed best....but this 10 is doing the job. I drop 1-2 gears is all, on most mountains I've climbed. The jake is very quiet too, but strong. I stay in top gear and just let the jake do the work on downhill. 6% I will nudge the brake pedal a couple times. Just came down that 7% on Hwy 64 cross the Allegheny the same way...n-o-o-o problemo.

[Jackrabbit379]

I havent seen the 389 in person yet. I want to though. I bet it's pretty. I want to drive one. Ooh la la.

[Roadhog]

Jack...she is sweet. Looks very much like the 379...but the closer you look...the more you see rounded edges.
They are slight...and not as radical as I was braced for.
:evil: I hate change. :evil:

But...this change is nice. Still have flat glass windshield seamed in the middle.
I hate rounded windshields! Same narrow cab...(so no lardbutts allowed..:P)
Cowl mounted stainless air cleaners as before. Sweet looking 7" stacks.
Headlights are more streamlined, but still mounted off the radiator cowl as before.
They are using mirrors now...like whats on my 387. The hood is 4" longer....
'cuz of the bigger radiator...and air flow needed for underhood heat.
(a problem on the 379's)
Front Disc Brakes!!!! I saw them while I was at Meritor in Heath-OH.

[Roadhog]

Hey...thanks to Malaki...I just learned you can view the RoadKing rag online. Here is an article on the 389, with a few photos.

http://www.roadking.com/story.php?id=879

[allan5oh]

You can't just go by the HP peak or the HP curve and say "that's gonna get good fuel mileage".

A 475 HP ISX will get better fuel mileage then a 475 HP c15

A 465 HP volvo will get better fuel mileage then a 475 HP ISX.

etc...

[PackRatTDI]

[Eaton still lists the 15 speed transmissions in it's sales literature section so I would assume you can still order one. The problem is that it's only rated to 1650 lb/ft of torque so if you're in the market for a big HP engine with 1750lb/ft or torque or better, the 15 speed isn't an option.

So does that mean if someone wanted to order a Pete 389 with a 625 HP Cat and a straight ten-speed it wouldn't be available and instead would have to go to an 18-speed? 8)

If they wanted to keep any kind of warranty they would have.

[Jackrabbit379]

Jack...she is sweet. Looks very much like the 379...but the closer you look...the more you see rounded edges.
They are slight...and not as radical as I was braced for.
:evil: I hate change. :evil:

But...this change is nice. Still have flat glass windshield seamed in the middle.
I hate rounded windshields! Same narrow cab...(so no lardbutts allowed..:P)
Cowl mounted stainless air cleaners as before. Sweet looking 7" stacks.
Headlights are more streamlined, but still mounted off the radiator cowl as before.
They are using mirrors now...like whats on my 387. The hood is 4" longer....
'cuz of the bigger radiator...and air flow needed for underhood heat.
(a problem on the 379's)
Front Disc Brakes!!!! I saw them while I was at Meritor in Heath-OH.

Uuummmmmm. Oooh ahhhhh. Oh man, I want to see one. 8) :P

[Birken Vogt]

Not really completely on topic but the article mentions making an 80 psi brake set...who makes an 80 psi brake set??? I consider it hard if I go to 40 and if I am really standing on them I might see 60

Birken