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4020 transmission pump

O

ostate67

New User
i have my '65 4020 transmission pump laying on the table. what do i look for to determine if it has excessive wear ? thanks !!
 
Pull the cover off and remove the gears, rub your finger down the sides where the gears wear into the housing and feel the lip..If it's worn much at all replace it, and look at the end play in the top shaft, if there is too much the shaft will work up and down whittling at the pump housing since the gear is on that shaft..
a92800.jpg
 
the only "evident" wear is where drive gear has worn a bit on the back face of the housing. with your comments and being this deep into it i believe i'll just replace it and move on. related question, i'm installing a new check valve in the elbow outside of the oil filter relief valve. it is ok to leave the old check valve and spring out of the flow line isn't it ?? thanks so much
 
again, thanks tim. probably be back to bend your ear when i start on the high pressure "chatter" side of the system. dean
 
It's possible the high pressure chatter will be eliminated or reduced with increased low pressure system flow.
Also look for any leaks or restrictions in the low pressure circuits. Who knows what bit of filter O'ring could be wedging a relief or divert valve open.
Is the 4020 PS or synchro?
 
If it's a SynchroRange and not Powershift - all that gear pump has to do is keep the front pump wet. No pressure needed for the front pump to work properly. If it's so worn it no longer pumps any oil - you'll see it easy from the obvious wear.
 
LJD the transmission on a synchro-range trans is lubricated by the trans pump. No trans pump and you will trash the top shaft and related parts!
 
(quoted from post at 17:58:55 12/16/12) If it's a SynchroRange and not Powershift - all that gear pump has to do is keep the front pump wet. No pressure needed for the front pump to work properly. If it's so worn it no longer pumps any oil - you'll see it easy from the obvious wear.
Click to expand...

I was thinking trans pump on a synro-range was suppose to supply 5 GPM & 150 psi.
 
Yes that is the specs for them but a sychro range will work fine with less than half that, the main thing that shows up is it looses prime or has more drain back and then it takes a bit longer to pick it back up, this shows up when your backing a wagon and the clutch is down a bit longer as you steer the wheel, they will tend to cavitate or run out of oil to the front pump, causing you to loose steering.
 
Yes, but the front pump requires NO pressure to work properly. It just has to be kept wet. Many other tractors with similar if not the same pump gears need higher PSI to run other functions besides the front main hydraulic pump. Same goes with a 4020 with Powershift.

When you plug a gauge into the hydraulic pump (if it has a charge test port) any pressure over zero is excess. When you provide more oil then can be used - pressure builds up. Thus the 5 GPM @ 150 PSI test specs.

My point is - if someone is trying to diagnose a hydraulic problem - when it comes to the main pump and main system hydraulics - it makes no difference to the front pump if it's getting 1 PSI or 100 PSI. As long as there is any pressure on the feed side - it will work the same.

Many early 2.4 and 3 cubic inch main pumps do not have the extra test port for charge pressure. When they do - it is easy to just screw in a 200 PSI gauge and run the hydraulics. If it stays anywhere above 0 PSI, you know the main pump is getting all it needs.
 
I never said anything to the contrary. I said the main pump in front needs NO feed pressure to operate correctly. just flow. That was true when I stated it, and is still true now.

There can be many other reasons why a trans pump is needed in various Deere tractors and option packages - but it is not what my comment was referring to. Some tractors need the trans pump to power hydraulic trans clutches, PTO clutches, lube for bearings, etc. The main pump only needed to be fed oil and if it can be kept "wet" with 1/2 PSI it will work fine. If charge pressure drops to 0 PSI, then you can assume the pump will start to starve once it uses up what is in the overhead reserve tank (some have it and some have no reserve).
 
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