Explanation of Axle Ratios?

[underthegun]

Can anyone help me understand what the different axle ratios are best utilized for. I am looking to buy my first truck and want to be as well educated as possible. I will be running a super regional area out of Florida and any consideration given this request is appreciated.

[showtrucker]

Originally Posted by underthegun

Can anyone help me understand what the different axle ratios are best utilized for. I am looking to buy my first truck and want to be as well educated as possible. I will be running a super regional area out of Florida and any consideration given this request is appreciated.

Well either I will leave you more "dazed and confused" or maybe i'll make sensible the many mysteries of gear ratio...First consideration what kind of freight ? I mean as far as setting up a truck going super heavy or air freight there is quite a difference in setting one up...For example my 78 kenworth was custom built with a six speed main transmission and a four speed auxillary (two sticks) both overdrive with 3:90 rears...obviously you don't need something like that most folks don't even know how to drive one of those anymore....My 97 pete has a 10 speed direct with 3:70 ratio and runs on 11x24.5 "tall rubber" and is decent for most general freight hauling..if i had "ordered" this truck i would have went with a 18 speed or a 9 speed overdrive as with the direct transmission it doesn't get great fuel milage at cruising range...If only i could slow down and keep my size 15 out of the radiator......If now i am serious was just starting out with my "first truck" (i paid 2500.00 for my first one) i would go with a freightliner fld with a 12.7 detroit engine...9 speed trans..3:70 rears or maybe 3:55 rears air ride of course.... buy with records have the truck dyno tested at the detroit dealer (hey it's money well spent if you know nothing about the history of the truck) and make dang shure you have a "WARRANTY" not some scam repair contract.......ok fozzy boot me if you want my uncle is 77 and losing his sight to glaucoma he has a 2006 pete not the 379 but the aerodynamic model (somebody help me on the model) also my truck is for sale due to the fact that i need cash for hospital bills...e-mail me showtrucker@yahoo.com for further info..

[pepper45]

(Oh, I just cracked myself up!!! I thought he meant axle "weight" RATIO'S...lol lol) What a good laugh on me!!
Anyway, here's what I wrote since I don't know a whole lot about gears and rear ends (cept my own)...

"Best utilized" for?

To keep your butt from getting a ticket.( lol)

To answer your question, though, axle weight distribution and restriction serves a number of purposes. The main goal in mind is Safety. Every single axle truck, dual axle, ect. has a gross amout of weight that it can legally transport, and, its broken up into axle weight. Equal distribution of the load makes for safer operation of the truck, and even, a better ride.

In rating the vehicles weight, this sets a standard for say example, the tire manufacturers. They then have to produce a tire that can handle this weight. Our roads and bridges are also rated for "x" amount of weight. Not every road can handle the maximum amount of weight of whatever Commercial vehicle you may be driving, so, it's important to know the Gross weight your vehicle is rated for, the gross weight AND axle weight of EACH load you haul, and, also know the route that you'll be driving. You also need to know the "Bridge Laws", how it's formulated, and how they may vary from state to state.

If you really want to learn, study your FMCSR. Here's a link. Part 658 covers Weight.

http://www.fmcsa.dot.gov/rules-regul...fmcsrguide.htm


Also, you can go up to the search here in this forum and type in "axle weight" and get a ton of info from the archives.

There's also a TON of info in the front and back of a good Atlas.

These should be a few places to get you started.

Good Luck!

[toomegamisfedrvr]

Excellant posts by showtrucker and pepper.

I have never purchased a truck but if I did, I'd "go to school on specing" since this may be the most importatant consideration for the satisfaction of the truck for your use.

Here's one lead :

Calculations
When spec?ing, you need to know ahead of time how the truck will perform, how well it will start uphill, how well it will hold its speed on a long grade, and approximately what kind of fuel economy you can expect. There are formulas that will tell you how much horsepower you will need to maintain speed up a 0.5 percent grade, or how much torque is required to hold a gear going up a 1.5 percent (or 2.0 or 2.5, etc.) grade. Other formulas will tell you what percent grade you can start on. Here?s an example:

Startability = S = T(800) x Ra x Rt x M/10.7 x GWT(800) = Engine torque at 800 rpm (clutch engagement speed)
Ra = Rear axle ratio
Rt = Transmission ratio
M = Tire revolutions per mile
GW = Gross vehicle or gross combination weight
10.7 = The constant that makes the result work out to be a percent.

For on-highway use, S should be at least 16.

A good article from Landline Magazine, concerning specing can be found here....hope it's helpful and good luck.

http://www.landlinemag.com/Archives/...techniques.htm

[pepper45]

Now, THAt was funny. I laughed so hard at myself , I almost cried. I bet I even wind up with some "cow dung" on me from "somewhere"....LMAO

I kept thinking "Dang, he don't know how to scale a dang truck, and he's gonna BUY the durn thang?" Stranger things have happened.

[toomegamisfedrvr]

Hey pepper !....a good laugh is a treasure, no matter where it came from....hope you are continuing to improve.

[underthegun]

Thanks Folks I appreciate all the replies I have been around the business for many years but never paid attention when it mattered. When I was coming up my father had about 150 trucks on the road but he sold out about 15 years ago. Of course he would not hear of one of his kids driving trucks so at the ripe old age of 18 I went to work at the State Prison. It has been a colorful career including a 3 year suspension starting in December of 99 for an excessive use of force issue, he stabbed me and I still carry his steel in my hip. I am now about to start my 24th year and do not plan on being there anymore. July 15th will be my last day and I will retire at that time I will cash in my Retirement and buy a truck for cash.

While I was suspended I drove over the road and loved it but it was for some one else who was controlling my destiny. I spent a year with Core Carriers out of Jacksonville Fl which is now owned by National Freight and 2 years with a Company lots of people seem to dislike Super Service out of Somerset Ky. Super was really good to me but some people will whine if you were to hang em with a brand new rope. Fast forward to the present I want to just jump in head first and sink or swim. I am looking at a 2005 Century Class 500 HP 13 Speed 3:58 Rears 304,900 Miles on it. With a full warranty package through Freightliner and I plan to pull Containers out of Jacksonville Fl on a Super Regional Route. The reason for the question is they have 3 trucks with 3 different Rears 3:55, 3:58 and 3:70 and I just wanted the best option for both pulling and fuel mileage. Thanks again for the assistance.

[toomegamisfedrvr]

Not a bad starter truck at all....Many of us would prefer the Columbia over the Century, if it were an option....hope you've done a lot of preplanning....some of the big boys say you may be looking at $4.00/gal fuel this year....thats with the present refinery outlook and not allowing for whatever affect Iran may have.

The experts are laying odds you're going to lose your tail....but....????

[showtrucker]

Originally Posted by underthegun

Thanks Folks I appreciate all the replies I have been around the business for many years but never paid attention when it mattered. When I was coming up my father had about 150 trucks on the road but he sold out about 15 years ago. Of course he would not hear of one of his kids driving trucks so at the ripe old age of 18 I went to work at the State Prison. It has been a colorful career including a 3 year suspension starting in December of 99 for an excessive use of force issue, he stabbed me and I still carry his steel in my hip. I am now about to start my 24th year and do not plan on being there anymore. July 15th will be my last day and I will retire at that time I will cash in my Retirement and buy a truck for cash.

While I was suspended I drove over the road and loved it but it was for some one else who was controlling my destiny. I spent a year with Core Carriers out of Jacksonville Fl which is now owned by National Freight and 2 years with a Company lots of people seem to dislike Super Service out of Somerset Ky. Super was really good to me but some people will whine if you were to hang em with a brand new rope. Fast forward to the present I want to just jump in head first and sink or swim. I am looking at a 2005 Century Class 500 HP 13 Speed 3:58 Rears 304,900 Miles on it. With a full warranty package through Freightliner and I plan to pull Containers out of Jacksonville Fl on a Super Regional Route. The reason for the question is they have 3 trucks with 3 different Rears 3:55, 3:58 and 3:70 and I just wanted the best option for both pulling and fuel mileage. Thanks again for the assistance.

Really not a whole lot of difference there as far as ratios go ...from a mechanics standpoint (then again i am 6'4'') i find the century hard to work on as far as engine also look at what if any resale value it will have...they've basically been referred to as "throwaway trucks" as far as residual value....even with the best fuel milage available it'll still be rough....guess you must have worked at raiford if i were to venture a guess anyways good luck with it and stay safe ...