Calling all 4020 powershift experts!

[Hay maker2]

Ok, my 1965 John Deere 4020 powershift started to slip last summer, most noticeable while in 7th & 8th gear going up hill with a load. I am for sure all the gears slipped a bit, but was not noticeable.

Now we have owned this tractor since 1970 and the power shift has never been worked on so I was and I am not afraid to go the extra mile and replace something extra (O-rings / seals) since it is 50 years old and been a reliable work horse.

I borrowed the test gauges (the unit with all 7 gauges on it) and checked the clutch and brake packs. C1 & C2 had 50 psi on them and the C3 and the brake unit all had 160 psi. The PTO also had 160psi.

I resealed the planetary pack even though the pressures were good and replaced a few O-rings and seals here and there because there was a drip and there was no better time to replace them then now.

I disassembled the C1 & C2 clutch pack and all of the separator plates and friction plates looked great and I took them to my local dealer and they agreed that there are nothing wrong with them. This was a well seasoned mechanic that has been at the dealer for almost 40 years. He has worked on and rebuilt everything under the sun and he is always spot on, he knows his stuff. I replaced all the seals in the C1/C2 clutch pack and replaced the seals in the supply pump. This includes the 4 sealing rings that transfers the input shaft to the C1 drum. I also replaced the "plug" and sealing ring on the output shaft that transfers power to the planetary pack.

For good measures I also opened and replaced the O-Rings, Seals, and springs in the shift valve (aluminum housing) and speed select housing. Like I said, its 50 years old and I have no problem going the extra step.

Since the tractor was split, I installed a new pressure plate, springs, and a rear engine oil seal (seal was not leaking) and new gaskets and O-rings between the rear end and clutch housing.

Now, I started the tractor up and I still have the same 50 PSI on C1/C2 and everything else still has the 160 PSI. Before everyone asks, yes I did swap the gauges around to confirm that there was 50 PSI on C1/C2 and that there was not two bad gauges.

At this point I studied my service manual and decided to replace the speed control spools and the shift valve (aluminum housing and valves) because I felt that there may of been blow by at this point.

To my surprise when I started it up to night, I still have 50 PSI on C1/C2 and everything else remains 160 PSI. I am at a loss and looking for any suggestions.

The only thing that I can think of at this time is that the C1 clutch drum may have some grooves worn into it from the sealing rings, but I inspected that when I took it apart and it appeared to be fine. It was shinny where the rings ride, but I could not feel any grooves in it. I also made sure that I used the correct sealing rings since there are three different ones based upon serial numbers. Other than the clutch drum, what's the chance that there is a crack in the clutch housing allowing oil pressure to blow by????

Thanks for any and all help!!!!

 

[Bob]

I'm at the house in town for the night, away from my manuals, but what is in common between Clutch 1 and Clutch 2 that would be causing the same pressure issue to both?

 

[Tx Jim]

Hay maker2
Sounds as if you covered your bases very well. I think as you stated that you must have enough wear in drum although not visible at sealing ring area for pressure lose.

 

[rick deere]

on a power shift you must only use only john deere hygard and every yr replace the filters on the trans even if you don't use the tractor, and you also at least once ck the screen in the bottom, ck for metal particals.This is so very important.

 

[Hay maker2]

Yup...
This is all done on a regular basis. When I opened everythign up the screen was clean and I used new filters and new Hy-guard oil. This is like religion to me, yes you can get cheaper oil, but in the long run it will cost you alot more!

(quoted from post at 14:48:04 11/05/15) on a power shift you must only use only john deere hygard and every yr replace the filters on the trans even if you don't use the tractor, and you also at least once ck the screen in the bottom, ck for metal particals.This is so very important.

 

[rick deere]

it must be what john deere sales no tractor supply, its not the same

 

[rick deere]

one more thing what most people think is a clutch, is not, only use at start up, after that don't use it again,your power shift will last much longer.

 

[Hay maker2]

Have owned the tractor since 1970 and never had an issue with the powershift. There is around 12,000 hours on it and been using the clutch (inching peddle) religiously since the day we bought it.

 

[rick deere]

has issue now

 

[Hay maker2]

your right that I have issue with it now....

But after 50 years of use don't we all have issues? Do you really think that this is not a normal use issue or do you honsetly think that this is becuase the inching preddle was used for the last 50 years?

How many times will you have to replace a dry clutch in a syncro 4020 over a 50 year span????

 

[rick deere]

All I really know is the best mechanic Id ever met whom is now pasted on told me to keep my foot off of it and I never questioned him now im in my mid60z and I always listen to those whom have been there and done that . Sounds like you've had a very good tractor and Id get it fixed if you wanted to keep it.

 

[tim s]

Here is the shift chart for it..

 

[Hay maker2]

thanks, but already have that in my service manual.

(quoted from post at 19:34:12 11/05/15) Here is the shift chart for it..

 

[Tx Jim]

(quoted from post at 13:21:45 11/05/15) All I really know is the best mechanic Id ever met whom is now pasted on told me to keep my foot off of it and I never questioned him now im in my mid60z and I always listen to those whom have been there and done that . Sounds like you've had a very good tractor and Id get it fixed if you wanted to keep it.

All the inching clutch pedal controls is a hyd valve and the valve is either closed or open. IMHO operating clutch pedal has nothing to do with the durability of the PS trans.

 

[D-]

Don't worry about the pedal. I to will disagree with Rick on that.
How does your manifold look. Many times the ring grooves are worn
along the sides (where the four rings are).
I would bet the reason your drum is not worn in the ring sealing
area is those old tractors had a stainless steel sleeve there.
Later the rings rode on the cast.

 

[Hay maker2]

I have a new drum on order, should be here tomorrow. It will be my Saturday project and I will post back, hopefully with good news!

IMHO, the inching peddle is no different then the remote outlet, your just opening and closing a valve. The tractor is 50 years old, and if you think using the inching peddle is going to damage the powershift your crazy. Isn't 50 years of use enough to prove that the inching peddle does not damage the powershift????

 

[grwrench]

hello,the powershift in your 4020 is pretty much bullet proof, as you have seen, and using the pedal is NOT
detrimental to trans. life, as long as the operator does not ride the pedal. how about checking to be sure the
pedal or linkage is coming ALL way to the home stop, because if you watch your gauge for clutch port on the
traction valve, you will see the gauge read full pressure ALL WAY UP AND START TO DECREASE as you push the pedal
down to bottom where it should read "0" i had a tractor awhile back that started slipping in the trans. and found
the pedal was not coming ALL WAY UP. so i freed up the linkage and i may have adjusted the linkage to move the
valve deeper into engagement. be sure the spring on the clutch valve inside is ok.

 

[Hay maker2]

Yup...
That was the first step that I took. The pressure will increases / decreases smoothly as I press or depress the peddle. I was crossing my fingers that was the issue as that would of been a simple fix. I can also see how it is easy to overlook that aspect of the issues.
Thanks

 

[rhtx55]

Are the pressure readings the same after driving it around a bit, shifting though the gears ? Reverse ?

 

[Hay maker2]

Making progress. I opened the old girl up and replaced the C1 drum. This time I paid closer Attention the bore that the sealing rings ride on and you could notice (feel some wear). I replaced the drum and closed it up. I checked the pressure once again...

C1 and C2 were 50 PSI and everything else was 160 PSI. Now C1 & C2 are running 110 PSI, better but still not perfect. I'm starting to think that D is on to something as he stated the grooves in the manifold were the sealing rings ride are worn and causing blow by. I will be ordering a new manifold come Monday.

I double checked everything else, still 160 PSI on the port for the clutch pressure and still 160 PSI on the PTO. I even swapped gauges around to double check that I don't have a defective gauge...

 

[Tx Jim]

Thanks for update. It's good to hear you're making progress.

 

[fdt860]

Just curious:
If there is a leak in the system, why some clutches are still operating at normal pressure and not C1-C2? I would think that if there is so much leaks that pressure drop, it has to drop everywhere??
Problem is in the pressure control of C1-C2 or in the dump valves?

(Not an expert at all in PS, just asking questions)