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4WD frontaxle for JD 7920 (R/C 1:16)

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While I wait for some parts for the Kverneland plow, I thought I would start building a new frontaxle for the JD 7920.

The plow features a mechanical system that puts pressure to the frontaxle via the topshaft. Up to 1 pound of pressure just by pulling the plow….. !!!

All that would not be used at all with a normal 2WD tractor. So that triggered me to start building the new axle.

Some details.

The axle will have it’s own gearmotor. It have the exact same gearratio as the rearaxle but the front diff. is 1,5:1 and rearaxle is 2:1.

The differential works by 2 ‘one-way’ needlebearings. When it runs forward the axle is actually locked (diff. lock). But in turns the outer wheel spins faster than the innerwheel. (power to innerwheel only = 3WD). ‘One-way’ means that I will only have 4WD when it runs forward and 2WD in reverse.

The complete axle will feature 14 bearings in different sizes.

The basic diff is almost done, much more to come…..






Take care!

Anders Kolpen

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Here is a little update to the frontaxle I am building.

It's a little rough and square, but it is going in the right direction.

The ‘differential’ is done and ready to mount in when the housing is completely done. Still a few things to do on this part. I can’t wait to test this new axle on the tractor…. :)



More to come…..

Anders Kolpen

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I'm glad you know what you are doing because I have no idea! What I do know though is; as far as active members go there is nobody in the same league as you.

Anyone (of which there are only three or so on FTF) using brass gets my full attention but the workings and maths you must have to do to source the right parts or to make the right parts is where you are right at the top 8)

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  • 1 month later...

Hello everybody

Here is an update to my 4WD John Deere 7x20 frontaxle.

Almost ready to paint, but there is still some touch ups to do. The little ball in front, fender brackets, wires + prepare the old wheels to the driveaxles.

Here is some photos.

Comments are welcome as usual.








Anders Kolpen


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