Wi | BurkFarms - 6/24/2014 15:26 Found a nice 98' KW T800 with pretty low original miles (565,000) that I'm interested in. It is priced right but what scares me off is the 3.08 gears. It does sit on 22.5 tires but gears still seem awful tall. I also have no experience with the M11 motor. Lots of cummins on the farm but no M11 I pull a 34' timpte and a 40 Kaufman drop deck with 3000 gallon tank and 2-4 cage shuttles of chemicals. I'm in no powerhouse now with a Frieghtshaker Columbia C12 (380 hp) and 3.73 rearend. Truck is an 04' in very good mechanical condition with 468,000 original miles but I'd like to get into something else. Don't need to but would like too. Am I going to be asking for driveshaft troubles or will I be ok?
Rear ratio means nothing without transmission ratios. Big spread is possible, not so much on top gears but there are a lot of low gear options. Some have 14.80 ish lows, others have 10.00 ish lows.
Here is some simple numbers to help you in your truck search without actually driving the truck. You will need the transmission model number then just google it for the ratios.
In this case the NAT approved ideal is apparently 5mph at full throttle in the lowest gear. We'll use 2000 as full throttle even though an M11 will go higher. You also need tire diameter. For simple math 22.5LP is 40", 11522.5/24.5LP is 42" and 11r24.5 is 44". We know the rear end ratio is 3.08.
(2000/5)(336.1355/42)*3.08*5=16.23 is the desired first/low ratio. For quicker math here are some helpful numbers.
336.1355*40= 7.64
336.1355*42= 8.00
336.1355*44= 8.40
When you're looking at a truck, first look at the tire size then pick the proper number from above. Then look at the rear axle ratio and multiply the two numbers together. Examples
8.00*3.70= 29.60
8.40*4.11= 34.52
7.64*3.36= 25.67
If you have a target ground speed multiply that with the number above. Examples.
29.60*65= 1924
34.52*5=172.60
25.67*15=385.05
The above number is the engine RPM's at that speed when in direct. If you know your transmissions ratio simply multiply it by the number above. Examples.
1924*0.73=1404
172.06*10.86=1874
385.05*4.12=1586
If you do not have the ratio but have a target RPM you can find the desired ratio by simply dividing the target RPM by the RPM when in direct. Examples.
1500/1924=0.78
1800/172.60=10.42
1600/385.05=4.16
I'm not going to spell out all of the rest, but its simple algebra. Take the data you know, use it to solve for "x". The data you wish to know. |
3.08 gears with 400 HP M11
