Transmission Fluid Level

I bought a used JD 2640. Right now it's running OK, but the last couple of times out, it ran fine for a while, then the hydraulics quit. Last time it ran great for about 5 hours, the hydraulics starting failing, so I parked it.....by the next morning it worked fine. Today it ran fine for an hour, then the hydraulics quit again. I let it sit for two hours and they started almost working.....a lot of chatter.

When it's cold, the trans level is a tad over the upper level on the dipstick, and when idling in neutral, a tad under the low. So I go home and admit ignorance and looked up the official way to check the fluid......it says put it in park and have the clutch engaged to check it. I'm not with the tractor now, so I'll check that next time I go to my property.

Would a low level cause my symptoms? or might it be the hydraulic pump?

Well I hate to tell you that you more than likely have more serious issues than low fluid or the main pump.

The working when cold and quitting when hot are more of an indicator of clutch pack leaking after it is warm. You will need to tell us how your JD 2640 is equipped. Hydraulic PTO is standard. Hi-LO shift is an option or a hydraulic reverser. All three of these have hydraulic clutch packs.

Even knowing this your going to need gauges and knowledge/manual to figure out the issue. How mechanically inclined are you??? These tractors have a hydraulic system that works great when everything is working correctly. When it fails it can be time /money consuming to repair it.

Where yours works fine when cold and then stops is usually not a plugged sump screen. Thinking about it more it could be too. Drain the hydraulic oil out of the transmission/rear end. There are caps on each side right in front of where the three point arms pivot.# 29 is the cap and #27 is the screen. remove this cap and pull the screen out. HOPE IT IS CLEAN!!!! Check this out before you use the tractor much more. If it is plugged by brake material you do NOT want to spread this through the entire hydraulic system. Doing that can make this into a very expensive/lengthy repair.

I hate it when guys buy JD Mannheim utility tractors and have hydraulic troubles right away. Usually the tractor had hydraulic issues before they bought it. The prior owner just cleaned the sump screen and installed a new filter then shipped it down the road. Passing the problems along.

I am not joking about how this could be costly. If it is just the rear brakes it can easily be $1000-1500 with labor. Hope like heck it is just that. Bad brakes can easily ruin the transmission pump too. Add in another $100-1500 parts and labor. If the material is though out the hydraulic system is just gets worse.

I did a JD 2020 three years ago. They had ran it until it totally quit. Family Heirloom type of tractor. So they wanted it fixed regardless of cost. Just under $10K total in parts and labor just on the hydraulic related systems with brakes too.

Ditto what JD Seller stated.

Is tractor equipped with a frt end loader? If so what type valve controls FEL(scv or ind)?

With 3 pt raised,engine running look in hyd filler hole behind seat for moving oil. If you see moving oil that indicates leaking 3 pt control valve seals that if leak bad enough can cause hyd's to fail.

I changed that transmission screen not long ago......just a few hours of operation ago, actually. It was very clean.....it didn't really even need changing, but since I had a new one, I installed it anyway.

What I didn't change was the small screen on the hydraulic pump in the front. Could it be that?

I think.....I think mine is the standard PTO. It does have a front end loader. I don't know what type of valve it has. A few months ago I did look in the access hole behind the seat and didn't see any spray.

The front hydraulic pump is likely original.....any chance it's just that pump going out?

The chattering your hearing is the main pump starving for oil. So it is trouble behind that, low pressure/charge circuit. You can replace the main pump and still have the same problem. The main pump on these tractors rarely causes any trouble. It is just about always in the low pressure circuit. You either have an internal HIGH pressure leak that is leaking more oil than the charge/transmission pump can pump or a leak in the low pressure circuit. The low pressure charge circuit feeds the main hydraulic pump. That same circuit supplies the oil for the PTO clutch, brakes, and the Hi-LO or Reverser if equipped. Regular PTO would be hydraulic operated on a JD 2640. You should have a lever between the gear shift levers that turns the PTO on and off.

These tractors are also known to break/crack the steel lines that come up the PTO control valve. This would cause a leak in the low pressure circuit. You can check these out by removing/lifting the gear shift cover off. Not the entire top cover just the smaller one for the gear shifts and PTO control valve.

An over view of how your system works. The charge/transmission pump sucks oil in through the sump screen and filter. It pumps about 6-8 gallons a minute at 175 PSI. This is the charge or low pressure circuit. This oil provides the pressure for the PTO, Hi-LO,Brakes and Power reverser. It also fills a reservoir above the main hydraulic pump and oil to the main pump. The main hydraulic pump provides 2250-2300 PSI at 14-15 gallons per minute flow. (Numbers are off the top of my head. They are close enough for theory of Operation) So you can see the problem. The main pump can pump twice as much oil as the transmission pump. The system was designed to operate short stroke hydraulic cylinders, rockshaft cylinder and 3x8 remote cylinder. You pull the lever and a 3x8 cylinder strokes and your done. The oil in the reservoir and the transmission pump can easily keep up for this type of operation. The trouble comes in when your using longer cylinders( loader lift cylinder as example) and hydraulic motors. So you have to have the return oil routed back to the main pump so it can pump at its maximum volume. If you dump it to the sump then the transmission pump can not keep up and your main pump cavitates and chatters. The same thing happens if the low pressure/charge circuit has internal leaks. So there is not enough oil pressure and flow for the main pump to operate. These leaks are most commonly caused by cracked internal pressure lines( PTO and Hi-Lo circuits), or leaks in the clutch packs in the PTO, Hi-Lo, etc. Some times you can have high pressure internal leaks in the three point valves/piston, SCV valves, and external loader valves. The SCV and loader valves can be checked by checking them for heating up after the tractor runs for a while. You can look through the hydraulic oil filler cap and see the rockshaft cylinder/valves if they are leaking. More rare things are steering valves. which makes the steering column get hot. Stroke control or pressure regulating valves in the main pump.

Long and short these tractors are hard to diagnose with gauges, manuals and knowledge. Near impossible over the internet.

Only way to determine if frt hyd pump is failing is proper diagnostics. Many closed center hyd pumps have been replaced to determine that pump wasn't the problem.

Does frt end loader have an independent control valve mounted on loader or is it controlled by selective control valves on the tractor?

Cheap hyd test is to cap hyd line that supplies power steering,then operate tractor to see if hyd's operate better.

(quoted from post at 20:06:29 06/25/18) These tractors are also known to break/crack the steel lines that come up the PTO control valve. This would cause a leak in the low pressure circuit. You can check these out by removing/lifting the gear shift cover off. Not the entire top cover just the smaller one for the gear shifts and PTO control valve.

Click to expand...

The large steel lines underneath are indeed old and have had issues in the past.....someone brazed a few spots. I was going to replace them but the JD dealer told me they were not available.

If one of these was leaking, would it suck air into the system? Or would I see a spray when the tractor is running? Or a drip when it's off?

Thanks for all your help.....this is most helpful.

Also, for what it's worth......this tractor was recently split and has a new clutch. My mechanic and I replaced the clutch and seal. My ignorance will show again.....what is a clutch pack? We didn't do anything to the transmission. It's possible there is a leak in the low pressure system somewhere, I suppose. It's just weird that the hydraulics would run when cold, then stop after an hour or two.

Bump