Problems shimming JD 445 hydraulics

[Turbo Goat]

Hey tractor people,

I'm taking my first stab at modifying my 445 hydraulics. Aaaaaaannndd something's weird.

The first issue that I discovered was that the stock hydraulic pressure was 750 PSI. Not a good sign, but not necessarily a show-stopper. Second, the stock IRV seemed to be missing some packing and a washer, and it was also very worn. The brass shim was deformed into an oval in the ID, and the plunger cone was visibly worn. I received a new IRV today and began shimming. I pretty consistently get less than 50 PSI for each 0.3 mm shim. So at 1.2 mm of shims, I get 900 PSI. Now this seems WAY low. I can't reasonably put any more shims on and I think it would be asking for trouble anyway. I'm about to conclude that the charge pump needs an overhaul. However, I could be missing something. So I want to ask the community for a sanity check.

The hydraulic fluid is full. The fluid and filter were very recently changed. The fluid is HyGard, Low Vis. Pressure is measured at W.O.T.

My assumptions are:

1) The stock hydraulic pressure in a properly functioning system should be about 950-1050 PSI.
2) Most people that have made this mod get around 1250 PSI with 0.5-0.6 mm of added shims.
3) It is OK to measure charge pump pressure at the bucket wrist, raise port (top left looking forward).
4) It is OK to use a cheap 2000 PSI gauge, cobbled together with some fittings from ebay to measure the pressure.
5) Visible wear on the IRV sealing surface is indicative of a problem. This problem could have been caused by the missing packing, allowing the plunger to wobble.
6) The machine has about 2000 hours on the meter, and I suspect that it was not so well maintained. It's a '97. So, some wear is to be expected.
7) A charge pump rebuild is improbable, and replacement of the transaxle is likely the only solution.

When I ordered the IRV, I thought about ordering the valve seat as well, but the JD parts diagram doesn't give a number for it. I'm not sure if valve seat wear would have an impact on pressure when mated with a new plunger. I'm not sure if I could get it out of the transaxle case anyway.

Just for giggles, I have to more gauges on the way. I don't completely trust a $10 gauge from Ebay.

If anyone has any ideas, questions that might lead to a solution, or useful info, I would really appreciate the help.

 

[zzvyb6]

JD or WIX filter ?

 

[Spanner]

Without answering any of your questions (yet) what prompted you to commence this 'mod'? Did you have 'low' hydraulic pressure?

Charge pump replacement, alone, is possible. The viability of repair is dependent on your budget, means, condition of the rest of the machine and what you are using it for.

You can try lapping the relief valve into the seat. You would dismantle the transaxle to do this anyway so you're half way to a rebuild.

 

[Turbo Goat]

JD or WIX filter ?

Not sure. The dealer changed it. What are the implications of one vs. the other?

 

[Turbo Goat]

Without answering any of your questions (yet) what prompted you to commence this 'mod'? Did you have 'low' hydraulic pressure?

Charge pump replacement, alone, is possible. The viability of repair is dependent on your budget, means, condition of the rest of the machine and what you are using it for.

You can try lapping the relief valve into the seat. You would dismantle the transaxle to do this anyway so you're half way to a rebuild.

Spanner,

Thanks for the info.

My reason for wanting to increase the hydraulic pressure is that the loader can only lift around 200 lbs. A loader that can't lift at least a level bucket of gravel isn't that useful to me. I discovered the issue when trying to lift my newly acquired 3-point tiller out of my pickup. That was a total no-go. Of course I understand that this is a garden tractor. It is limited in what it can do without damage.

I believe that I have low hydraulic pressure. I measured 750 PSI. However I plan to verify with a second gauge. I have the second gauge and might be able to do the test this evening.

I have the budget, and probably the means, but it's a bigger project than what I really want to get into. The over-all condition of the machine is 7 of 10. It's worn, and rough around the edges, but runs great.

Goat

 

[Spanner]

Understood Goat.

FWIW I think you will be wanting to operate the old 445 at 10/10ths capacity often. Maybe you should sell it and buy a bigger machine which can handle your workload at 60-70% with room to spare?

You start stripping the 445 rear-end and the wallet may open wider than you want. :2cents:

 

[Turbo Goat]

Understood Goat.

FWIW I think you will be wanting to operate the old 445 at 10/10ths capacity often. Maybe you should sell it and buy a bigger machine which can handle your workload at 60-70% with room to spare?

You start stripping the 445 rear-end and the wallet may open wider than you want. :2cents:

Thanks. I do appreciate the advice. I was hoping, perhaps naively, that I wouldn't be operating so close to the limit.

And my wife won't let me get a bigger machine. :laughing:

 

[Spanner]

Maybe need to trade her in with the tractor? :stirthepot:

 

[zzvyb6]

Not sure. The dealer changed it. What are the implications of one vs. the other?

I saw on another help site where a 445 had the same issue and a change from WIX to a JD filter 'solved' the problem. Of course, just changing to a new filter might have done it, too though.

 

[Turbo Goat]

I saw on another help site where a 445 had the same issue and a change from WIX to a JD filter 'solved' the problem. Of course, just changing to a new filter might have done it, too though.

zzvyb6,

Thanks. I'll check the filter make when I can get back to the tractor.

Goat