4020 Transmission Question

Bill VA

Well-known Member
Spending a little reading and getting schooled on the JD4020 tractors, history, early vs late, etc. Very common to see a 4020 on Craigslist around here.

I see the 4020 came with a synchro range tranny (to me that reads sync'd like a truck, changing gears via a clutch) and a power shift tranny that really uses no clutch? Nearest thing is an inching pedal to ease hooking up to implements?

I gather the synchro range is simple and reliable, easy to repair/service? Wet clutch? Going down hill with an implement or hay wagon being pulled, notorious for jumping out of gear?

I assume the power shift tranny is more complex and with it a more expensive fix/service vs the synchro range? Wet vs dry clutch is a non issue as the PS can start/stop without depressing a clutch? Are these tranny's bullet proof? Is the design of the PS tranny such that it is impossible to jump out of gear going down hill with loaded hay wagon or heavy towed implement in tow? With either tranny, are the brakes reliable, easy to service, effective at stopping the tractor? Are breaks necessary to slow to a stop with a PS tranny, do you get engine braking when downshifting?

Which version sold more, PS or Synchro Range tranny.

Just curious.

Thanks!
Bill
 
4020 synchro has a dry clutch and the tranny is not particularly notorious for jumping out of fear under ANY conditions unless badly worn.

Powershift still has a dry clutch at the flywheel, a "torque limiter", and in the earlier serial numbers it can be disengaged with a separate little lever to make cold weather starting easier. Inching pedal disconnects one of the wet clutches in the tranny.
 
I worked for a JD dealer back when 4020s were still fairly new but the 30 seies were prevelent. We did a number of clutches on the synchros but I don't remember ever touching a PS. If used right and oil levels maintained they seemed to be pretty bullit proof. I am sure they may be more expensive to ovehaul if needed but they just seemed to "keep on running" like the energizer bunny.
 
I worked for a JD dealer when 4020s were starting to age and the 30 series was still new. We put a number of clutches in the synchro tractors but don't remember ever touching a PS. I am sure they can be damaged by low maintance but just seemed to keep going and going.
 
I have owned several of both transmissions, and have had less trouble with powershifts. They are good dependable tractors with good brakes and hydraulics. And you can downshift a powershift to slow down.
 
We have four 4020's and five 3020's right now and all are syncro-range. A clutch is a wear item and usually last 4000+ hours under normal use. Half the clutch jobs are done because the rear engine seal starts leaking and soaks the clutches with oil causing it to slip. I did twist a center out of a clutch but that was my big tractor and the fuel was really turned up and it was way overworked. I like the syncro because I know how to work on them. Nothing wrong with a powershift but you can spend alot of money to rebuild one.If you look at a powershift make sure that the pto stops, many do not and the pto brake is in the rear of the trans case so you must remove everything to service it. Tom
 
The PTO brake is in the second split section and is exposed as soon as that split is made nothing inside the trans needs to be removed to replace the brake. It is NOT at the back of the transmission.
 
Pto brake is right at the rear split on both PS and synchro tractors. It takes more labor on power shift models as you have to split at the flywheel first, remove the front clutch packs, and then remove 2 bolts for the rear split from inside the clutch housing. Synchro models just remove the trans cover and you have access to all of the bolts for the rear split.
 
Both transmissions were pretty darned tough, but today the newest are 44 years old. I have 2 syncros and 1 power shift (4020s), plus a 2510, 3020, 4320.

As far as sales data goes, it is sort of a guess. It would be a fair guess to say in the earlier years, (64-68) the 4020 sales were probably 35-40% power shift. In the later years, that probably drops a little- to say 25-35%. Probably not due to anything wrong with the power shift, but instead a tightening of the farm economy during the very late 60s and early 70s. And also, when the PS came out in 64, the "early adopter" crowd wanted all the new features. By the fall of 1970, the 4020 was living in the shadow of the 4320, 45-4620, and 5020 row crops- all bigger horses with row crop features introduced after the 4020. The "early adopter" probably moved on to bigger horses to a degree. This also probably had influences in sales.
 
OK I just learned something. A Deere mechanic told me years ago that to fix the pto you had to remove the clutch packs. I have never had a powershift apart but have done a dozen or more syncro tractors. How much time would you figure to put a pto brake in a powershift? I see them at sales with a pto that will not stop and it really hurts the sale price. Maybe I should take a chance and buy one as there would be plenty of people on here that could give me some advice as far as fixing it. Thanks Tom
 
The labor in those is only half the issue. At least with the early ones, it is possible (maybe more like common) for the housing the brake fits into to be damaged... meaning replacement of the housing, or some fancy machine work. There was more than one update on those systems early on- I think one in '65 and one in '66 to try to "heavy" things up a little. There are several serial number breaks when looking at the PTO brake assembly.

The main thing with a powershift 4020 is to idle down implements with big momentum (batwing mowers, forage blowers, etc) before disengaging the PTO.
 
The first thing to do is confirm that it is a pto brake problem and not a linkage problem. There is a short arm on the control valve that has a habit of coming loose on them. Remove the lower dash panel and follow the pto linkage to the lower left side where it fastens to the back side of the valve. Make sure the nut holding the arm is tight and if not, be sure it engages the flats on the valve shaft before tightening. Labor for the split, probably 3-4 hours to get it apart (double split, front clutch packs on bench) depending on lines coming loose and assuming no cab or loader. Now is where it gets costly sometimes. I always re-seal the trans pump and front packs while they are out. You may find damaged clutch disks in any of the 3 packs (c1, c2, and pto)as these are the packs controlled by the inching pedal and pto lever and subject to slipping and operator abuse. It can be the proverbial can of worms or it can be all in good shape but hard to tell from the outside.
 
I rebuilt the powershift in my 1965 John Deere 4020 last fall. There was about 9000 hours on it and it has never been touched. We have owned the tractor since 1969 and highly doubt that is has ever been opened prior to last fall.
I personally like the powershift over the syncos, its just my opinion.

One thing that no one has stated prior in this post is that the powershift has a constant running transmission pump which feeds your main hydraulic pump. On a synco if you press the clutch in and hold it in, you will eventually loose hydraulic pressure as no oil is being supplied to the main pump. Also the powershift works better with a loader as it is easier to shift and as stated a constant running transmission pump.

You should be able to have the PTO brake pulled out in about 3 hours on a powershift, at least that is what it took me last fall.
 

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