L4850 mechanical ratio

[Ironbrew]

I'm dealing with tires... I'm trying to find the mechanical ratio for the L4850 so I can look through tire sizes.

Thanks

 

[rbargeron]

I've posted about this in some posts here (see link below).

The term "mechanical ratio" is sometimes used to describe 4wd tractor traction differences front-to rear. There's another formal term called TRANSFERENCE RATIO which compares front and rear gearing, showing the differences in axle turns vs engine crank turns.

Then, using the dimensions of the tires being used, the distance covered in each revolution is computed. The INTER-AXLE RATIO is computed by dividing the two theoretical distances.

Most 4wd tractors are set up to "scuff" 3-5% when going straight ahead (fronts pulling). One reason for this is to still get some net assist at the front when turning right or left.

I believe the L4850 has the same gearing as my L5450. If so, your TRANSFERENCE RATIO is the same as mine, which I calculated using available L5450 parts data at 1.508

My rig has R4 industrial tires, 12x16.5 front, and 17.5x24 rear. Using the calculated TRANSFERENCE RATIO of 1.508the INTER-AXLE RATIO calculates with R4 tires at 1.037 (fronts pulling around 3.7%). If your L4850 has R1 Ag rubber, its TRANSFERENCE RATIO is the same, but with 11.2x20 front and 16.9x28 rear the INTER-AXLE RATIO is a bit less at 1.028 (fronts pulling around 2.8%)

More related posts here - scroll up and down. Take care, Dick B.

 

[Ironbrew]

Thank you

 

[Ironbrew]

I've looked it up in the service manual, and yes those tire sizes cross over for your R4's. The R1's don't cross over to the 4850 according to the chart.

I found a set of R3's at a price I couldn't pass up on (basically very discounted rims and free turfs). The Front turf is a slightly different size (I'm trying to find out if it will matter) and that's part of what dragged me into all this digging. The front turf is 29x12.00-15 instead of 29x12.50-15. The circumference difference is 86" vs 91.1" (edited - depending on model and make, the variances can be basically nothing to 5" circumference difference - meaning I'm probably stressing over nothing.). It might reduce or eliminate or increase the front tire scrubbing from the factory desired numbers but is it within tolerance? Still digging...

 

[rbargeron]

Turfs can be more tolerant. Other factors that affect the scrubbing one way or the other also include inflation pressure and whether you're driving it on paved surfaces or not. Maybe just get in the habit of using 4wd only when needed ?

 

[Ironbrew]

Turfs can be more tolerant. Other factors that affect the scrubbing one way or the other also include inflation pressure and whether you're driving it on paved surfaces or not. Maybe just get in the habit of using 4wd only when needed ?

I try to anyway...

 

[rbargeron]

My friend has 45k bushel orchards that need spraying often this time of year to control fungus and bugs. When pulling a 2-ton sprayer, you don't get a second chance to put it in 4wd. You're stuck and there's a lot of money in the tank - the materials degrade in water, so waiting for a tow costs every minute as the insecticide breaks down. All their tractors stay in 4wd all the time rather than chance it, especially years like this when the ground is getting soaked a lot. There are several sides to everything....

 

[Ironbrew]

I'm fairly fortunate in that I mostly don't need it except for plowing. Come snow, it'll be 4wd full time till spring.

 

[North Idaho Wolfman]

Yea I never take mine out of 4wd, I have too many hills and situations to not have all the traction and braking that I can have, all the time.