Final Drive questions - Not a gear/hydro thing

[jeffghs]

Can someone explain the differences in the different final drives in tractors? John Deere seems to be the only brand that lists this in the specs, so I have been looking a little more closely at JD, but would like to see some comparisons with other brands as well.

As I understand it, there are several types of final drives spur gear which is what most companies use in their compact utility and utility lines from the best I have been able to find. Planetary gear which is used on the JD 990, 4510 and up, and the 4000 - 20 series. It is touted by JD to be what is used in heavier ag equipment and has a little more substance to it. Last, there is the helical which is used in the new JD 3000 - 20 series. I haven't heard much about these and may even be another name for a spur gear.

Does anyone know of any exceptions to other brands using anything but a spur gear? Has anyone ever had a failure of a final drive assembly?

Really, just wanted to see if this was a factor to consider before purchasing? My needs are not anything out of the ordinary from most here. Thanks.

 

[frank_f15]

i sure can't help you! /forums/images/graemlins/grin.gif i don't know to many folks that take into account the type of final gear drive in a tractor, before their purchase. But will be interesting to see if some of the more informed members can help.

 

[RalphVa]

I just noticed the external stuff like my 4010 rear shafts come straight out of the diff; whereas, the 2210 shafts were offset. Think this is how they lowered it.

Ralph

 

[Ledgemere Farm]

Planetary distributes the load over several (normally, three) gears, whereas spur is only one. Spur is fine on smaller tractors where weight and torque are less. John Deere's larger tractors, such as the Five-thousand-twenties even have planetary final drives on the front axles.

 

[Soundguy]

Some other points toponder.. a spur cut gear is a straight cut gear.. cheaper to manufacture.. and a bit noisier in operation. Helical gears are just that.. helical cut. Harder to manufacturer.. and also quieter.

Ever see a tractor where the rear axle comes out of the diffy.. then to side gear boxes.. then tire/hub is mounted to the gearbox.. that is an example of a 'final' drive where there is a gear ratio change between the diffy and the wheel. Other tractors simply have the rear axle driving the rear wheel directly from the diffy, thru the axle trumpets...
Many front 4 wd axles would have an example of this as there is usually a final drive at the end of the axle for 'final' gear reduction, and power distribution ( depending on the type of 4wd scheme.. )

soundguy

 

[Kiohio]

I don't know why others don't list it in their specs. It is a more expensive but stronger final drive. I do know that Kioti uses it(Planetary gears) in the DK45,50,55,65 tractors. I have also noticed alot of size differences in the different brands. How thick the cases are where the final drives are located and such. Varies quite a bit from brand to brand.

KO

 

[keeney]

Planetary gear systems are used where torque requirements are very high. For example when using large diameter wheels in applications that require high drawbar pulling forces.

The advantage is not so much the additional gear surface area, since you could always design a wider single gear with the same contact area. The problem is that a single spur gear pushes against one side of the ring gear. The other end of the torque lever is the axle bearing. The axle bearing thus sees a side-load equal to the force at the spur gear face. With large wheel diameters and small ring gear diameter (for ground clearance), the force may be considerable.

Also, as the axle rotates, the side-load it sees is constantly twisting around to a new direciton. This constant flexing of all the various parts can lead to stress failures and other issues requiring a beefing up of the whole axle design fopr high torques.

A planetary gear system does not derive its torque by pushing against the axle bearing. It is torquing on the axle from three or more sides all at the same time, and the side forces cancel each other. There is little or no force exerted on the axle bearing other than the machine weight and loads. All the force from troque drive is transmitted through the planetary gear faces.

Planetary gear final drives are also good for high-torque applications like large-diamater (24-36") augers used for planting trees, for example.

 

[jimg]

I found this in my travels and though it applied to the discussion. Im not sure what a double reduction spur is or why its better or worse than any other final drive...Ill leave that for the final drive experts. This is a pretty interesting discussion though. Just to put things in perspective...whats the practical difference between a spur gear set up and planetary in practical in the field use? That is, would I ever notice or care in the working life of my machine given that I didnt abuse it?
http://www.ohiotractor.com/New_Equipment/MF/1445_comp.pdf#search='final%20drive%20tc45%20new%20holland'

 

[KiotiJohn]

</font><font color="blue" class="small">( I found this in my travels and though it applied to the discussion. Im not sure what a double reduction spur is or why its better or worse than any other final drive...Ill leave that for the final drive experts. This is a pretty interesting discussion though. Just to put things in perspective...whats the practical difference between a spur gear set up and planetary in practical in the field use? That is, would I ever notice or care in the working life of my machine given that I didnt abuse it? )</font>
A planetary is always better than a spur gear just by the nature of the makeup, but if not abused, most spur gears should hold up well enough. John

 

[Kiohio]

Planetary drives are quieter and have less backlash.

KO