‘64 4020D Syncro Hydraulics

[CTW71]

I’ve had this tractor split (new rear end,tranny top shaft, clutch plates, flywheel and associated clutch adjustments). Put rock shaft housing back on and finally got 3pt moving then it suddenly stopped working and steering is rough. Coupler on hydraulic pump appears ok upon inspection. Notice a ltl chatter under dash and one of lines running from dash to rear svc vibrates a bit. Any ideas on where/how to solve this one?? Thanks!!

 

[Tx Jim]

Sounds typical for an internal hyd leak. One will need to perform some hyd diagnostics. After hyd's operate then stop check each hyd control valve using a laser thermometer for valve with highest temp probably being the problem

 

[CTW71]

Thanks Jim…..any ideas likely potential internal leak points?

 

[rabrac]

Did you check out the transmission pump located in the differential housing and the sump screen located below. The other thing that could be causing loss of hydraulic pressure is that the main front pump needs to be de-stroked there maybe a piece of debris caught in one of the valves on that rotor pump. The transmission pump is the one to supply oil to the front main pump. You could also take the top center link attachment bracket off. Located behind that bracket is a threaded plug remove it and then carefully remove the hex drive shaft for the transmission pump and see if the shoulders of the shaft are rounded off where it mates to the transmission pump. The shaft is long, going all the way to the main clutch. The shaft is only engaged when the clutch is release. John Deere finally made it drive directly off of the flywheel on the 40 series tractors, so then disengaging the clutch didn't stop the transmission pump from turning. The rockshaft housing would have to be removed to repair or replace the transmission pump.

 

[grwrench]

hello,, if it is a 4020 it does NOT have the hex driveshaft,, that came out in 1973 with the 4030---4630

 

[rabrac]

Okay sorry I could remember if the 20 series were set up with the hex shaft or if that was the 30 series. Been a few years since I worked on a 4020. Thanks for the update.

 

[CTW71]

I put the transmission pump back in (had to remove to replace top synchro shaft which drives pump). Everything appeared to go in correctly. Also, I have run the tractor several times with zero problems steering, brakes etc. problems did not manifest until I aligned cam roller w the ltl arm inside rock shaft housing. 3 pt lifted flawlessly a cpl times then stopped. In addition, there was a knocking sound coming from what seemed to be front (main pump) coupler. The knocking stopped and problem started. However coupler turns shaft in pump w motor running. Maybe pump is just shot???

 

[Tx Jim]

Good hydraulic diagnostic procedures need to be performed before entertaining the idea of replacing any hyd component more especially a hyd pump! It's possible a piece of foreign material is keeping stroke control valve from seating properly. Does your tractors frt hyd pump have a destroking screw? DS screw is item in photo in green circle. If so with engine operating at idle speed turn DS screw clock wise to stop then CCW to stop. Hopefully if foreign material is in SC seating are it will be dislodged & pump will commence pumping.

 

[CTW71]

Thx Jim! I will check.

 

[Tx Jim]

You're welcome

 

[CTW71]

Btw, it appears to require an Allen wrench

 

[Tx Jim]

What are you referring to that needs an Allen wrench?? JD didn't offer a destroking screw that accepts an Allen wrench!! Sounds as if you're referring to "stroke control valve adjusting bolt" which adjustment should not be changed without monitoring hyd pressure with a hyd gauge.

 

[CTW71]

Sorry, I tried DS and that didn’t work. I was referring to what appears to be the round access point just behind transmission filter. I assumed that was the long screen. It appears to have a larger than 3/8” Allen hole in center. Am I looking at wrong access point for screen?

 

[Tx Jim]

You're correct round plug between hyd filter cover & rear axle housing is where hyd oil screen is located. Hit plug with a hammer several times before attempting to remove the plug.

 

[CTW71]

Thank you!!

 

[grwrench]

hello,, it is a 1/2 '' allen wrench

 

[CTW71]

Thanks GR! I knew it was larger than my 3/8”)……I actually hit it a cpl of times w mallet and used vice grips to turn. Screen looked fine. I strained the fluid thru filter to refill and turned the DS valve on main pump a cpl times…….steering seems a bit better. Starting to wonder if maybe the little cam got out of its slot inside rockshaft housing even though it worked (lifted 3pt) a cpl times??

 

[Tx Jim]

If 3 pt hitch raises/lowers when moving control handle then I'll bet cam follower is in correct location in 3pt control linkage.

 

[CTW71]

Thx Jim,

In light of my diagnostics thus far….any suggestions re: where you’d go next if it’s in your shop? Thx!

 

[wore out]

Thanks GR! I knew it was larger than my 3/8”)……I actually hit it a cpl of times w mallet and used vice grips to turn. Screen looked fine. I strained the fluid thru filter to refill and turned the DS valve on main pump a cpl times…….steering seems a bit better. Starting to wonder if maybe the little cam got out of its slot inside rockshaft housing even though it worked (lifted 3pt) a cpl times??

Does the hitch valve warm up quicker than the rear end casting?