John Deere 4020 Powershift

[Pennerosa]

Hi just bought my first ever 4020. Ran terrible when I picked it up but with adjusting the injector pump timing and installing new pencil injectors it runs like a dream now! But have an issue with the power shift. It often does not want to go forward - have to shift from reverse to forward a few times before it will go. However, once it is moving forward, it has all eight gears and I can shift up and down all I want and does not miss a single shift. But if I shift to neutral or reverse, same problem again. Also, when cold the trans pressure gauge reads good pressure, but as it warms up it drops off some. I am sure I need to split the tractor, but I am not sure what the likely cause is. Any advice? The previous owner had just changed the trans fluid and filters to see if that would help before he sold it, but he said it made no difference.

 

[Dieseltech]

DO NOT get in a hurry to split it. Sounds like the forward/reverse spool valve or other valves are sticking. My 4020 did the same thing in times past but has not done it for over a year now.

 

[wore out]

Hi just bought my first ever 4020. Ran terrible when I picked it up but with adjusting the injector pump timing and installing new pencil injectors it runs like a dream now! But have an issue with the power shift. It often does not want to go forward - have to shift from reverse to forward a few times before it will go. However, once it is moving forward, it has all eight gears and I can shift up and down all I want and does not miss a single shift. But if I shift to neutral or reverse, same problem again. Also, when cold the trans pressure gauge reads good pressure, but as it warms up it drops off some. I am sure I need to split the tractor, but I am not sure what the likely cause is. Any advice? The previous owner had just changed the trans fluid and filters to see if that would help before he sold it, but he said it made no difference.

Was the transmission sump screen removed and cleaned?

The "trans pressure gauge" actually reads transmission lube pressure which can be affected by lots of things, even including a "high pressure leak to sump" in the main hydraulic system, you need a factory tech manual and follow it's diagnostic "trees" to narrow down any possible issue(s) before blindly splitting/tearing into it.

As the the forward/reverse issue. very likely that is caused by the parts circled in red.

The "reverse bellcrank" (13) can wear as can the "finger" on the shift lever that operates it. The linkage rod and clevis, etc. can get out of adjustment (14, 15, 18). You can try adjusting the rod and clevis to add a little movement to the "forward" position of the shift valve and take a little from the reverse side.

But first, grab a spray can of your favorite LUBE and oil the shift mechanism in the quadrant in the area of the bellcrank.

If it's rusty/sticky/gummy in that area some lube can make a big difference in how the forward/reverse works.

 

[Pennerosa]

Wow thanks this is all really helpful! Will check into these things.

 

[Tx Jim]

Pressures in each gear selection need to be taken/recorded before considering splitting tractor. IIRC each gear selection have 4 pressure ports in each gear selection. My guess is problem you're experiencing is is in shift valve or linkage not trans.

 

[JIM MN]

Did you check the transmission oil operating pressure?

 

[Richard G.]

Hi just bought my first ever 4020. Ran terrible when I picked it up but with adjusting the injector pump timing and installing new pencil injectors it runs like a dream now! But have an issue with the power shift. It often does not want to go forward - have to shift from reverse to forward a few times before it will go. However, once it is moving forward, it has all eight gears and I can shift up and down all I want and does not miss a single shift. But if I shift to neutral or reverse, same problem again. Also, when cold the trans pressure gauge reads good pressure, but as it warms up it drops off some. I am sure I need to split the tractor, but I am not sure what the likely cause is. Any advice? The previous owner had just changed the trans fluid and filters to see if that would help before he sold it, but he said it made no difference.

Try changing the filters.
Worked on son's tractor.

 

[Fixingfarmer]

sometimes it’s best to start with what someone else already tried. Second the suggestion above asking did he clean or replace the pickup screen?

The good thing is it is working intermittently and a powershift has a couple external things to try first. Are you starting in 1st or like 3rd or 4th? I know the backhoe doesn’t find 1st most days

 

[Pirlbeck]

I would bet your problem is worn or misadjusted linkage, as I have seen this a lot in my almost 50 years of working on these tractors. .When it acts up take your hand and hit sideways on the shift lever knob. For reverse smack it (lightly) to the left and for forward smack it to the right, if doing this makes the tractor take off it confirms it is only a linkage problem. When doing this be prepared as the tractor will take off rather abruptly.

 

[Pennerosa]

Ok got it working now! Lubed the linkage and looked into where that suction filter that was mentioned is located. Would never have guessed there was a filter there! Drained the oil and pulled it out, and yikes! It was so bad I could not even clean it so just bought another one from John Deere (also replaced the other two filters while I was there - and it was obvious that they had just been changed when I pulled them out). Trans pressure gauge now reads great, and it works like a dream! Cut 15 acres of alfalfa with it yesterday with no issues. Thanks everybody!

Now another issue - the loader is very "jerky" when operated - that has not changed still. Where should I start with that for common problems? It has the style with the loader controls on the side of the loader, with the dash levers used for the rear outputs. When I am using an implement, the dash hydraulics work very quick and smooth for raising / lowering implements, but jerky with the loader.