936031 Hydro-Gear issue

First post here, glad I got invited by the sister site. Anyway, wife bought a new car so I'm stuck with old lawn tractors, our old JD LT180 lunched the TuffTorq hydro, so I went to refurbing this 2048 that had been sitting in the back for 5 years. Had to completely go through it changed most all the idlers and all the belts, drilled a hole in the Hydro-Gear and installed a plug so I could do a complete oil change with the correct synthetic. Started mowing for a few months limping along with it until I adjusted the valves in the intek 21HP before finally getting up to full power. Now I'm at the point where toward the end of mowing my 1 acre where it starts to struggle going up slight inclines. I have learned to do the one area with a larger incline first while it's still relatively cool, then the smaller incline next. But still would like to get more out of the transaxle.

New drive belt installed correctly seems pretty tight, cooling fan is missing 2 blades out of I think 8, debris is clear off the top of the hydro. I do notice the Transmission Disconnect Rod is kinda funky, it does work but doesn't really stay in the slot at all when I disconnect the trans. Where should I look next?

Mulligans have Hydros for very good prices if you want to stump up for one for either mower.
Hydros have to be bleed very carefully to get rid of all of the air.
If it looses power when hot then you either still have air in the system or need to go to a heavier grade oil.
Must use fully synthetic as std oils burn and the debris blocks up the oil passages.

Drilling the cases is a stupid thing to do unless you do it to an empty case from the inside out.
There are magnetic filters inside to catch tiny steel wear fragments but only a coarse mesh to pull out non magnetics like alloy.
Because the swash plate runs directly on the valve chest , you should always purge them on slow idle.

Yeah now that I think about it it's rather stupid to do it that way. I used 15W50 Mobil 1 in it. I might try and finish the season with it and drop it over the winter do it up right clean the filter etc. Thanks for the info.

One of my pensioner customers is running 20W 50 in his hydro which is shot because he "could not afford to get it looked at ".
He now has to mow his 3 acres over 3 days.
It is quite hilly so he starts off with the hills the as he looses drive he goes on to the flatter bits.

To quote the service manual from Hydro-Gear-

"Typically, an engine oil with a minimum rating of 9 cSt (55 SUS) at 230°F (110°C) and an API classification of SL/CD is recommended. A 20W-50 engine oil has been selected for use by the factory."

I live in Louisiana, operating temps are 90-95F for 4 months of the 8 month cutting season, and is never run at temps below 60F. What would you recommend?

I run full syntactic Valvoline 20w 50

BlazNT said:

I run full syntactic Valvoline 20w 50

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Yeah been looking around see who carries what, last time all I could find quickly was 15w-50. I see the auto parts stores carry motorcycle oil in the 20W-50 range, might get that.

paulbot said:

Yeah been looking around see who carries what, last time all I could find quickly was 15w-50. I see the auto parts stores carry motorcycle oil in the 20W-50 range, might get that.

Click to expand...

Ended up using some motorcyle 20/50 synth, drained the new oil out had shavings
floating in the oil. I have done the purge procedure 10 times , but it still starts slow and peters out after getting hot.Considering ordering a seal kit and pumgoing over the hydro hoping to get more life out of. Couple hundred in parts is worth it, but not the $7-800 range. What am I getting into?

In theory the hydo boxes are simplicity itself. a beautiful piece of engineering with few moving parts.

However if you look at the parts breakdown you will see the rotating valve chest runs against a stationary manifold plate with nothing between them to make a seal apart from some precision machining.
Similarly the pistons in the valve chest also have nothing to seal then except a close finish.
Thus any abrasive in the oil plays havock with the fine precision finish.
They are assembled in clean room conditions under positative air pressure to exclude dust.
Thus when you rebuild them you have to be anal about dust exclusion.
I do them in the bathroom after washing down the ceiling walls & floor.
Before I take the tranny inside it gets a degrease then a soad blast then a hot water wash to make shore there is no dirt on them before I pull them down.
Everything gets a bath in degreaser then the ultra-sound then goes in plastic sealing bags till they are needed for reassembly.
long rubber gloves and full painters paper coveralls complete with hood.
One set when I pull it down and a second new one when I reassemble.
I also set the video camera up on a tripod so I can review how it came apart before I put it together.
Big bits get covered with a damp fibre free shop towel.

To date only 1 I have rebuilt as failed.
Now I might be a touch anal but down here I have to warrant the job for 6 months.
Thus if I introduce grit with causes a tranny problem I am up for a new tranny.

Lots of videos which show blokes working on them on a grubby shop floor and then driving away with a perfectly working tranny.
They don't follow up in a year when the unit is totally stuffed.
Everything goes back in wet with oil and I purge the tranny with a piece of hose connecting the input shaft to a step drill in my 1/2" power drill.
If you are going to do it in your shed, wait till you are in for a week of solid rain before you reassemble it to clean the dust out of the air or if you are fog prone just after a heavy fog.

Thanks for your procedure, duly noted about the cleanliness aspect. So I'm guessing I have to tear it down see whats worn then order parts? Or is there a list of what's commonly changed out in a rebuild?