Help with hydrostatic trans

[TinkerJack]

Got a 1994 Yard-Man Model 998 with Peerless hydrostatic transmission - it's a project: the engine had a catastrophic failure, I removed it completely. I plan on repowering, but first I wanted to make sure the transmission is in working order. I drained the old fluid and replaced it with Premium Hydraulic Oil (J20C spec, just like the manual specified). After draining and installing new filter (FRAM PH16) I filled the trans with oil until it was coming out of the fill port on top. At that point, the dipstick was not showing the fluid... it almost looks like the dipstick has been broken or cut, it's pretty short, so that's the first problem/mystery - fluid level and short/broken dipstick.

The second problem has to do with priming the pump and purging the air out of the lines. Since I don't have an engine in this unit, I improvised an adapter to the pump shaft so I could power it with a drill. I lifted the back wheels off the ground with a jack and began to run the drill in CLOCKWISE direction - taking the clue from the fan cooling fan blades. My reasoning was that Clockwise rotation of the shaft would send air over the cooling fans of the trans, but I'm guessing.

Anyway, after powering the trans with a drill at different speeds: slow, medium and fast and trying to operate the hydraulic speed lever FWD and REV, plus the 3point hydraulic lever I couldn't get the wheels to run or get the hydraulic ram to operate. There is either air in the system, or the pump is dead.... (hope and pray not).

Need some help/advice, please.

 

[wore out]

Got a 1994 Yard-Man Model 998 with Peerless hydrostatic transmission - it's a project: the engine had a catastrophic failure, I removed it completely. I plan on repowering, but first I wanted to make sure the transmission is in working order. I drained the old fluid and replaced it with Premium Hydraulic Oil (J20C spec, just like the manual specified). After draining and installing new filter (FRAM PH16) I filled the trans with oil until it was coming out of the fill port on top. At that point, the dipstick was not showing the fluid... it almost looks like the dipstick has been broken or cut, it's pretty short, so that's the first problem/mystery - fluid level and short/broken dipstick.

The second problem has to do with priming the pump and purging the air out of the lines. Since I don't have an engine in this unit, I improvised an adapter to the pump shaft so I could power it with a drill. I lifted the back wheels off the ground with a jack and began to run the drill in CLOCKWISE direction - taking the clue from the fan cooling fan blades. My reasoning was that Clockwise rotation of the shaft would send air over the cooling fans of the trans, but I'm guessing.

Anyway, after powering the trans with a drill at different speeds: slow, medium and fast and trying to operate the hydraulic speed lever FWD and REV, plus the 3point hydraulic lever I couldn't get the wheels to run or get the hydraulic ram to operate. There is either air in the system, or the pump is dead.... (hope and pray not).

Need some help/advice, please.

Which side of the engine drives the hydro, the PTO side or the flywheel side?

 

[TinkerJack]

Which side of the engine drives the hydro, the PTO side or the flywheel side?

The PTO side drives the hydro. I've read that all B&S engines spin counter-clockwise when looking at the PTO side.
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Briggs and Stratton
Model: 350447
Type: 0119-01
Code: 93072211

 

[TinkerJack]

I'm seeing first signs of life from this trans. This morning I topped off the fluid level to the max, and cracked open the filter to make sure there is fluid making its way though it, also I moved the machine back and forth on the ground in different gears (hi and low) trying to get the fluid to make its way through the right places. At some point, I jacked up the back wheels again and ran the drill and when I pushed the lever FWD I noticed some movement in the wheels. I ran the drill some more, operating the FWD and REV positions and indeed I saw the wheels moving forward then back accordingly. There is no power in them yet, I'm guessing if I lower the tractor down and try to move it fwd and back it probably wouldn't go. I'm guessing it needs more power in that shaft than what my hand drill can provide. I also cannot yet operate the 3point ram - probably for the same reason. All in all, I call it progress and hope for more.

 

[wore out]

I'm seeing first signs of life from this trans. This morning I topped off the fluid level to the max, and cracked open the filter to make sure there is fluid making its way though it, also I moved the machine back and forth on the ground in different gears (hi and low) trying to get the fluid to make its way through the right places. At some point, I jacked up the back wheels again and ran the drill and when I pushed the lever FWD I noticed some movement in the wheels. I ran the drill some more, operating the FWD and REV positions and indeed I saw the wheels moving forward then back accordingly. There is no power in them yet, I'm guessing if I lower the tractor down and try to move it fwd and back it probably wouldn't go. I'm guessing it needs more power in that shaft than what my hand drill can provide. I also cannot yet operate the 3point ram - probably for the same reason. All in all, I call it progress and hope for more.

NOT sure about yours, but many hydro filters are on the suction side of the pump, if yours is like that loosening the filter would interrupt the priming process.

 

[TinkerJack]

While rolling the tractor around to a better location I started hearing some unhealthy clanging noises from inside the trans... like that missing piece of dipstick rolling around on the gears. Hard to describe it but it's intermittent and sounds metalic. I guess I'm faced with the reality of pulling that transmission out of the tractor and tearing it apart... how bad of a job is this?

 

[kencombs]

What is the RPM of the drill? Some 1/2" drills are too slow to operate the pump effectively. The closed to a gas engine idle speed you can get the better the test.

 

[kencombs]

NOT sure about yours, but many hydro filters are on the suction side of the pump, if yours is like that loosening the filter would interrupt the priming process.

True, and I think the is all hydro filters are on the suction as the filter can will not hold up on the pressure side, even just the charge pump output.
Like my little JD is set at 1200psi.

 

[TinkerJack]

What is the RPM of the drill? Some 1/2" drills are too slow to operate the pump effectively. The closed to a gas engine idle speed you can get the better the test.

I was in the process of mating an electric engine to the pump but I heard the metalic sounds in the trans... a little worried about turning it on full speed.

 

[TinkerJack]

Well, I got lucky - I hooked up a 2hp electric motor I have with a custom adapter sleeve that I made and fired it up. It works! Was able to run it FWD and BACK in High Gears and Low Gears. I was unable to operate the ram that lifts up the 3 point hitch... I have to get to the bottom of that (it's making noises like it's hitting the travel limit, but no movement). Still, it's much better results than I was foreseeing.

I'll post few pics of the sleeve adapter i made to connect to the drive shaft.

 

[TinkerJack]

Just finished testing the hydraulic ram that's responsible for lifting the carriage and implements. I completely disconnected it on both ends so that it's not doing any real work and started up the electric motor. When operating in the OUT mode, the ram moves extraordinarily slow... but when operating in the IN mode, it runs back very quickly. Wondering if that's a sign of a problem or if it's just due to the temporary setup.

The motor spins at 1720rpms, which is about 1/2 the speed that's required, so perhaps that's just the way it works at or near the idle speed of the regular engine?!

 

[wore out]

Just finished testing the hydraulic ram that's responsible for lifting the carriage and implements. I completely disconnected it on both ends so that it's not doing any real work and started up the electric motor. When operating in the OUT mode, the ram moves extraordinarily slow... but when operating in the IN mode, it runs back very quickly. Wondering if that's a sign of a problem or if it's just due to the temporary setup.

The motor spins at 1720rpms, which is about 1/2 the speed that's required, so perhaps that's just the way it works at or near the idle speed of the regular engine?!

When a hydraulic cylinder extends it requires enough oil to fill the entire area "under" the piston to complete it's stroke.

When the cylinder retracts it takes the same volume of oil minus the amount displaced by the piston rod.

So, yes, a common/typical hydraulic cylinder will retract faster than it extends because a smaller volume of oil needs to be pumped in to complete the stroke in that direction.