Switching John Deere 4020 to 38" rears

pmarkel

Member
I am looking into switching out the 34 cast centers on my 4020 for 38" centers. A gentleman contacted me in response to an ad I had in the Lancaster Farming and said he had a pair of 38" centers from a 3010 that would work but that I might need different wedges. He is going to contact me with the casting number but until then, I would like to hear if anyone on the forum has done this and what adaptations are necessary.

Thanks for the input,

Peter Markel
 
Not sure it would make a big difference, but the centers from a 3010 (38") vs those for a 4020 have a different number of clamps holding the rim to the center. And yes, the hubs will need to be changed. You
may be able to use the ones from your 34" centers.

As mentioned below, the drop center rims would be easier, and they work well. Plus you can go back to 34" easily.
 
On my 4020 I have 34 inch centers and some of my tool bars
would not clear a 38 inch tire. Might be something you want to
check before you make a switch.
 
Friend of mine picked up a set of lower arms for his 4020 and took the casting number from his old ones to match, same numbers but new set was longer.
 
You maybe able to used his castings with your wedges. What is your reason for wanting the 38 inch tires??? IF it is for ground clearance or road speed then you will be fine. Just remember that your changing the ground speed. When the JD 4020s where the "big" tractor on the farm and they did heavy tillage, making the jump to 18.4 38 tries just about eliminated 5 gear as a primary tillage gear. The increased ground speed would swamp the engine.
 

Yrs back I saw step up outside of rim clamps that allowed utilizing 34'' cast centers with 38'' rims. Ditto on needing longer draft arms with 38'' tires vs 34'' tires.
 
Step up rims are used a lot around here, and the percentage of speed increase is some but not much.. and most Original rims are usually rusted badly by now..
 
The 3 point hitch arms will work OK with 15.5-38 tires, check your tie heights before making a change. Many early 4020's had 15.5-38 tires for mounting corn pickers, there should still be some of those wheels in salvage yards. I think 4020's used 12 rim clamps and 3010's used 8, different castings and that may weight different too. Axle diameters were 3 3/8 inches on 4020's and 3 1/4 inches on 3010, 3020 and 4000's.
 
Just remember the 38 rear cast off a 3010 might be a bit light for a 4020. Years ago I picked up a set of 38" castings off a 4320 to put on my 4020 and they worked out real nice. Step ups are okay but i do like the look of correct size castings.
 
The 38" centers for the 3010, unless it has 20 series centers, will not be compatible with the wheel wedges of the 34" 4020 wheel. The angle of the taper on the wedges is different between the two centers. I was going to try to put heavy 38" 4010 centers on my early 4020 some years back. I found out the difference in the tapers firsthand. I used the step up rims on the early 4020 and they look and work just fine. Mike
 
(quoted from post at 06:38:46 08/01/17) The 3 point hitch arms will work OK with 15.5-38 tires, check your tie heights before making a change. Many early 4020's had 15.5-38 tires for mounting corn pickers, there should still be some of those wheels in salvage yards. I think 4020's used 12 rim clamps and 3010's used 8, different castings and that may weight different too. Axle diameters were 3 3/8 inches on 4020's and 3 1/4 inches on 3010, 3020 and 4000's.
he wheels are r31610. From what I can tell that particular center has 12 clamps?
 

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