[firebird_1252]

so while i get closer and closer to getting my work i'm coming across a lot of trucks. i'm making a lot of calls and asking a lot of questions.

so i was wondering what do you guys think is the best combo?

i know cat likes 3.36 gears

what about cummins and detroit?

i called about a t600 with a isx 10 speed and 3.70 rears the guy said the avg on the ecm was 6.3

i'm also looking at a 379 with a 500 detroit the guy that owns it now swares he's always in it and getting close to 6mpg.

could be a intresting topic.

[allan5oh]

There is simply no such thing. It really depends on the application. There is no "best gear" or anything like that.

What is the application? Max cruise speed? Average cruise speed? Area of travel? Max weight? Average weight?

[firebird_1252]

Originally Posted by allan5oh

There is simply no such thing. It really depends on the application. There is no "best gear" or anything like that.

What is the application? Max cruise speed? Average cruise speed? Area of travel? Max weight? Average weight?

i'd say max speed average cruise speed 65-70 area of travel could be anywhere. weight.. 80k?

basicly what motors have sweet spots? cat says 1400rpm for fuel economy and pulling.

mack i believe is 1700 but what about cummins and detroit?

[tracer]

Originally Posted by firebird_1252

i'd say max speed average cruise speed 65-70 area of travel could be anywhere. weight.. 80k?

basicly what motors have sweet spots? cat says 1400rpm for fuel economy and pulling.

mack i believe is 1700 but what about cummins and detroit?

you're mistaken about the cat. I got cat c15 with 2050 lb-ft torque. the ideal rpm for me is between 1300 and 1350. i changed the gear ratio so that now i do 62 mph at 1325 rpm. if the torque is less than 1,700 lb-ft, than cat says the most fuel efficient rpm would be around 1,400. the more torque the better.

[allan5oh]

Sweet spot is usually a misnomer, it's almost always a compromise between efficiency and driver satisfaction(pulling power). Talking about gears without talking about final drive ratios (transmissions) and tire size is pointless. Pick your engine first, then narrow it down to a gear ratio with tire size. Punch these specs into truckpaper. Gears can always be changed. Tire size can be easily changed.

I would suggest:

-Anything pre-egr, 02 and older detroits are very good motors. As well as the older cats(non-acert).
-If you can keep your cruise speed at or below 65, and can tolerate a 10 speed, go with 2.64 gears with a direct 10 speed. 11R22.5's or low profile 22.5's. This is probably the most efficient gear/tire combo out there.

[firebird_1252]

Originally Posted by allan5oh

Sweet spot is usually a misnomer, it's almost always a compromise between efficiency and driver satisfaction(pulling power). Talking about gears without talking about final drive ratios (transmissions) and tire size is pointless. Pick your engine first, then narrow it down to a gear ratio with tire size. Punch these specs into truckpaper. Gears can always be changed. Tire size can be easily changed.

I would suggest:

-Anything pre-egr, 02 and older detroits are very good motors. As well as the older cats(non-acert).
-If you can keep your cruise speed at or below 65, and can tolerate a 10 speed, go with 2.64 gears with a direct 10 speed. 11R22.5's or low profile 22.5's. This is probably the most efficient gear/tire combo out there.

a 10 speed i dont mind at all. i really prefer pre-egr.. but i do have a question on that. i found a 03 century midroof xt. anyway, it has a s60 in it 3.70 ratio. now it says new parts include a egr cooler. i thought for detroit the egr's started in 04?

also found a 2000 660 volvo 10 speed 3.55 gears and a 400hp ISM.

as of now it looks like ill be running fl to ny. or fl to tx. so no real hills.

thanks for the help guys.