Found My Ratios I Think

[Arcticmack]

Hey guys got my info from Mack and was wondering how to decifer the gvw rating of the rear axles,

I know the front is 12000 lbs, its a FA522 but Im not sure on the rears.. they are,, SWD57's...?? whats the rating on them also there ratios are 5.77 and according to my booklet information on my build sheet, the lo-lo 1st gear ratio is get this!! 18.96!!??

theres some stump pullin gears in this thing LOL

my 5th hi-split is .85 guess that would be the overdrive..?it has the Quadraplex.. just wondering how to tell what the final drive gearing would be and about what speed it should have at engine gov, 2100...or cruising ,,round here thats 60mph. with 1100x20 tires. thankx guys I know someone will be able to help me out or where to look.

thanks

Robert.

Edited November 28, 2008 by Arcticmack

[steve s.]

Robert,

SWD57 is a 38,000 lb bogie. It sounds like you have a transmission that is direct in 5th. The build sheet should tell you what model you have. There are some good road speed calculators on the web that will answer all your gear/ rpm/ tire size questions, do a search and find one you like. Steve

[ThaddeusW]

I came up with a formula where you plug in the engine RPM, trans gear ratio and rear ratio along with the tire diameter and it will give you the vehicle speed. I even wrote a simple program to compute it for you but never got around to polishing it up. I cant look now as I am going out but when I find the formula I will post it.

[David]

Final dtive ratio is 4.90 (5.77 X .85). Check out this road speed caculator.

http://www.roadranger.com/ecm/groups/publi...t/ct_062746.swf

[Arcticmack]

Robert,

SWD57 is a 38,000 lb bogie. It sounds like you have a transmission that is direct in 5th. The build sheet should tell you what model you have. There are some good road speed calculators on the web that will answer all your gear/ rpm/ tire size questions, do a search and find one you like. Steve

Well there not as strong as I was Hoping. but that'll do. there 5.77 ratios, and far as the tranny, it says Its DIRECT in 5th Direct, but in 5th Hi-split its .85 final. so guessing its an overdrive tranny.

[sdthoren]

.. just wondering how to tell what the final drive gearing would be and about what speed it should have at engine gov, 2100...or cruising ,,round here thats 60mph. with 1100x20 tires. thankx guys I know someone will be able to help me out or where to look.

thanks

Robert.

Robert,

I'll see if I can put my excel spreadsheet into words...

If you want to get speed in miles per hour, MPH;

1. start with this: rpm (revs per minute) * 60 (minutes per hour) gives engine revolutions per hour

2. then this: tire diameter (inches) *3.14159 => this gives the tire circumference

3. divide the tire circumference by: 12 (inches per foot) * 5280 (feet per mile) => gives the tire circumference in miles instead of inches!

4. now multiply the transmission ratio by the differential ratio (engine rev / driveline rev * driveline rev / wheel rev)

multiply items 1 and 2 together, then divide by items 3 & 4;

For your truck, this becomes: MPH=(2100rpm*60)*(43.1*3.14159) / (12*5280*5.77*0.85) = 55mph.

Not your 60mph quite cruising speed, but pretty respectable. I know I don't want to hit 70mph in my old dumptruck!

Just for grins, I looked at gearing and torque. Assuming an ENDT673 puts out 600 ft-lbs, your low end gearing of 18.96, your tire size (I assumed 43.1"), and good traction, you can put 6334 pounds of force to the ground! That's almost 800 pounds of force per tire from 1422ft-lbs of torque applied to each tire! OK, enough is enough, the geek engineer in me is starting to come out!

Hope you have fun with your truck!

Scott

[Arcticmack]

Robert,

I'll see if I can put my excel spreadsheet into words...

If you want to get speed in miles per hour, MPH;

1. start with this: rpm (revs per minute) * 60 (minutes per hour) gives engine revolutions per hour

2. then this: tire diameter (inches) *3.14159 => this gives the tire circumference

3. divide the tire circumference by: 12 (inches per foot) * 5280 (feet per mile) => gives the tire circumference in miles instead of inches!

4. now multiply the transmission ratio by the differential ratio (engine rev / driveline rev * driveline rev / wheel rev)

multiply items 1 and 2 together, then divide by items 3 & 4;

For your truck, this becomes: MPH=(2100rpm*60)*(43.1*3.14159) / (12*5280*5.77*0.85) = 55mph.

Not your 60mph quite cruising speed, but pretty respectable. I know I don't want to hit 70mph in my old dumptruck!

Just for grins, I looked at gearing and torque. Assuming an ENDT673 puts out 600 ft-lbs, your low end gearing of 18.96, your tire size (I assumed 43.1"), and good traction, you can put 6334 pounds of force to the ground! That's almost 800 pounds of force per tire from 1422ft-lbs of torque applied to each tire! OK, enough is enough, the geek engineer in me is starting to come out!

Hope you have fun with your truck!

Scott

your a genius.. keep the geekyness coming,

thank you for the help. Im sure that the 55 is good enough at least I know it will do that much all day long and never miss a beat,

[dak49]

Anything less than 1 is over drive, therefore a .85 is an over drive gear. Just take your gear ratio times the top gear ratio will give you your fineal gear ratio. 5:77 X .85 =4.90

I used another formula to figure your speed but it came out the same, 55@2100RPM.

Good luck

Dak49

[steve s.]

Well there not as strong as I was Hoping. but that'll do. there 5.77 ratios, and far as the tranny, it says Its DIRECT in 5th Direct, but in 5th Hi-split its .85 final. so guessing its an overdrive tranny.

. Robert,

All of the compound boxes have an overdrive gear, but the main box could also have an overdrive in fifth, which yours does not. So technically you have a direct transmission. Steve

[HK Trucking]

it says Its DIRECT in 5th Direct, but in 5th Hi-split its .85 final. so guessing its an overdrive tranny.

It's a TRQ72. Single overdrive quad box.

The TRQ 720, 7210, and 7220 would be the double overdrive versions of the quad box, with main direct in 4th.

[Arcticmack]

It's a TRQ72. Single overdrive quad box.

The TRQ 720, 7210, and 7220 would be the double overdrive versions of the quad box, with main direct in 4th.

Thats right it is a TRQ72 as it says in my build sheet.

so 55 is it Ive done some other figuring but thats what I come out with to9Thanx to those that pointes me in the right direction, and thats with 1100x24.5 tires.

cause the 1100x20 is the same height right? 43.3 or so inches in dia. thats what it says it came with 1100x20s. when I bought it has 1000x20s so there going bye bye anyways, in favor of new Budd disk steels with new tubless highway traction radials.

anyways thank you for all your guys input well taken and appreciated..

Robert