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#1851040 - 04/09/10 03:00 PM honda hrx mower slow, hydrostatic fluid/oil type ?
1 FMF Offline

Registered: 08/12/02
Posts: 1680
Loc: CT
long story semi-long, hrx217hxa, few years old now. initially the mower started getting slower one summer and this was after 2-3 years of use. so i pulled the drive out, figuring it maybe got low on oil or just needed a change. drained out the old oil, came out kinda nasty looking and sort of smelled like gear oil from what i remember. did a search, everyone seemed to say 10w-30 motor oil would work so i tried that. It was noisy and did not go any faster, no where near as fast when brand new. i felt the drive casing and it seemed hot, although i never felt it previously. pulled it out again and that's when i noticed the drive cable was all freyed, replaced that and then got full throttle on the drive but still noisy and didn't sound right. I then picked up amsoil hydrostatic trans fluid and have had that in there for past 2 seasons. And it only takes a couple ounces and i've gone through nearly a quart flushing and rinsing it out so i know there's no motor oil left in it. It's not noisy and it does run cooler compared to when i ran it with 10w30 motor oil but i still don't get full speed like when it was brand new... i like to cut grass at 4.0 mph! so my question is, is it possible the amsoil hydrost. fluid is too thin or too syntheticy and seeping/leaking past the hydrostatic pump in the drive resulting in loss of output? What other fluid should i try?
There seems to be zero information on these, some people claim they are made by tufftorq or whoever but i've called them and they don't admit to having one of their drives in it and what literature i got from them doesn't match the drive in the mower. And honda parts and mower shops all say it's a non-servicable part, there was no fluid to buy for it replace the whole drive for $300.
so my question is what fluid should i try to get back to 4.0 mph? I can't imagine it being some exotic fluid. it wasn't red so i know it wasn't atf, but should i try atf?
i'm pretty sure it wasn't basic motor oil when i drained it, it almost seemed like gear oil. I thought the amsoil hydrostatic fluid would've been good but i know it's getting full throttle and i can tell the output speed is not what it should be.
And for tractor or hydraulic oil, where can i buy just a quart? all i ever see is 5-gal pails.

#1852012 - 04/10/10 10:54 AM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: 1 FMF]
Craig in Canada Offline

Registered: 04/06/06
Posts: 1995
Loc: Toronto-ish, Canada
You sound like you know what you're doing, but I didn't see you mention resetting the cable tension/slack to factory spec.

My Honda Masters (HR215KHXC IIRC) slowed down noticeably after a couple of seasons and that's all it was. There are instructions in my owner's manual for setting the cable slack properly for normal operation.

Did you check this when you replaced the frayed cable?

I put Honda Hydrostatic fluid in mine, but I understand it's just 10W30 or 15W40 motor oil, really.

#1859033 - 04/15/10 08:31 PM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: Craig in Canada]
1 FMF Offline

Registered: 08/12/02
Posts: 1680
Loc: CT
figured it out,
the hydrostatic drive needs to be completely full of oil and completely purged of air. The way they made the unit so small there is no head space above the motor block in the case, and the fill hole is right above that. I had noticed that it seemed to get better when i had run the drive for a few minutes which was probably due to the fluid heating up and expanding. This time i got the unit on the bench and pulled it apart, figured out how it worked and realized it was nothing more than air getting pumped which was making the groaning noise resulting in the lack of output power/speed to the axle. So this time on the bench i filled the unit completely, the prior time i had not filled it thinking it would be overfilled and leak oil out the top. You also have to tilt it side to side a little to help get any air bubble out the top. Once i did that and spun it up on my bench with the drill i could tell the difference. So, the key is to make sure the unit is completely full.
Unserviceable my @$$ !
Oh, and i used atf... redline d4 only because i've had the quart for 5 years and have had no other use for it. Mower goes like it was new and is fast.

#1859077 - 04/15/10 09:23 PM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: 1 FMF]
1 FMF Offline

Registered: 08/12/02
Posts: 1680
Loc: CT
the hydrostatic drive from a honda hrx lawn mower, hrx217hxa to be exact.

here it is with the fill cap off and completely full of atf, before i had not filled it completely like this which was my whole problem. If you have any problems with a hydrostatic drive, it's most likely low on fluid and pumping air.

once out of the mower, take the lower block off first. you need to take this off first before you can split the case in half.

with the lower pump body off, you're now looking at the pump block. this is on the small vertical axle shaft which is connected to the pulley on top of the drive, the belt connects this pulley to the pulley on the engine just above the cutting blades. whenever the engine spins, this spins and is pumping but not driving the wheels unless the drive lever is pulled on the side of the unit. notice the little pin on the lower left of the pump block, just inside and to the right of the bottom left hole where the green gasket is. This is the lever that when you activate the drive, which rotates the swash plate, this lever comes up into the pump body which opens a valve and lets oil pump down through the lower pump body then into the motor block to drive the main axle shaft.

with lower pump body off, you can split the drive case apart. you will need to wire brush and polish the axle so the large side of the case on the left can slide all the way off.

as you split the case, the swash plate comes out. the pump block which was shown above rides against this swash plate. and below you can also see the motor block which is the same as the pump block just larger

here's all the parts to the pump block and pump shaft, and on the far left bottom is that pin that rides on the swash plate

here's another shot of the same along with the swash plate, couple thrust washers and bearing set

the motor block

installed back in the mower, what was said to be not serviceable has been serviced.

tools needed:
3/8" socket 14mm
1/4" socket 8, 10, 12mm; might want 12mm in 3/8
good pair of snap ring pliers- the axle shaft is secured via snap rings so you got to remove all these before sliding the axle out. A very small flat blade is helpful in getting under and removing the snaprings.
hard part will be getting the plastic bag/mulch shroud out and finding the 2 bolts that hold that in, one is on either the left or right side of the frame just in front of the rear wheel, the other is up in the bagging area of the frame and will probably be covered and hidden by solidified grass. After that, you need a strong hand to pull on the hydrostatic drive pulley to rotate the whole unit forward so the drive belt will go slack and you can undo the belt from the hydrostatic drive pulley. and to get the drive out it helps to remove the far side wheel/height adjuster bushing from the frame, it's secured via large snap ring on the inside/underside of the frame.

getting the drive on a bench is the hardest part. once there, it's pretty simple. You could probably use any oil. I used redline d4 atf figuring the 30-40 cSt viscosity at 40C would be ideal seeing how optimum viscosity for hydraulics is 20-35 cSt... higher viscosity than that and you lose efficiency due to pumping loss. I looked up some tuff torq fluid recommendations for their hydrostatic drives and they've superseded nearly everything with 5w-50 motor oil. And I had called tuff torq and they didn't admit to making this drive, there's no serial or casting number on it so I honestly don't know who makes it but it does somewhat resemble their k61 which you can download a pdf of and see very similar internal parts.
mobil 5w-50 has kinematic viscosity around 100 at 40C (a 5w-30 oil is ~60 cSt at 40C) which i think is too high but what do i know. I suppose if you never touch the unit, and with the oil contaminated with dirt and dust which I saw mine was when i drained the original oil, you'll end up getting wear which I suppose the higher viscosity could make up for. i also chose atf figuring it would be a better hydraulic fluid than motor oil and not be as likely to aerate, after all it gets pumped under significant pressure in an automatic trans and the same thing is happening in the torque converter. I still have a bit of amsoil 5w-30 tractor hydraulic/transmission fluid and i might give that another shot when i feel like pulling the drive again. but for now the atf seems to work great, and just to be clear i didn't use redline d4 atf because it's a synthetic, i chose it because i wanted to get rid of it and figured it had the most optimal (more near 25 cSt) viscosity at 40C of all the oils i had on my shelf. The amsoil 5w-30 i have is rated 50 cSt at 40C, so that's just slightly higher in viscosity. But so far with the atf i put some load on the drive for a few minutes and it was still cold, and it went pretty frickin fast; will find out in the next few weeks cutting the grass.

#2138501 - 01/14/11 03:47 PM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: 1 FMF]
1 FMF Offline

Registered: 08/12/02
Posts: 1680
Loc: CT
mower has worked excellent all summer, no problems with running the redline d4 atf in the hydrostatic transmission. No leaks, no problems with seal compatibility or anything like that.

thought i would send an update, since i am now considering spending some serious coin on a honda hs1132ta snowblower, it has their hydrostatic trans.

#2138547 - 01/14/11 04:24 PM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: 1 FMF]
01rangerxl Offline

Registered: 04/08/06
Posts: 9036
Loc: Birmingham, AL
Great write up, and nice work. Most of these transmissions that have ANY kind of problem just get scrapped.

Most owners don't even want to fool with replacing a belt. They definitely won't be changing the fluid in the trans.

From a shop/dealer perspective, there's no sense in opening the trans up to service it. Because of the labor involved, it makes more sense (with money and time) to just throw a new trans in and be done with it.

I'm not sure who the actual manufacturer of these transmissions is. We order them from Honda and they come in Honda packaging.
2002 Ford Ranger XLT | 3.0 V6 / 5-Speed Automatic / 2WD | 200K miles
1994 Ford Ranger STX | 4.0 V6 / 5-Speed Manual / 4X4 | 190K miles

#2139117 - 01/15/11 09:27 AM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: 1 FMF]
Errtt Offline

Registered: 11/14/10
Posts: 2617
Loc: California
This is good stuff and glad to see you figured it all out.
I also have the HRX.
$300 for the drive unit! wow - I also would get into it myself.

Put it off yesterday, so hope today it's dry enough to get the lawn done. Or I might tell one of the kids to do it and I'll go motorcycle riding instead. But if I get stuck with it and feel like it, the HRX will get a steam cleaning, oil change, blade sharping, cables lube, etc. Lawn may still be to saturated from recent rains.

#2139271 - 01/15/11 12:29 PM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: 1 FMF]
JTK Offline

Registered: 08/14/03
Posts: 9593
Loc: Buffalo, NY
Great work! Nice pics! Yes, I've seen air in the system cause owners to think their drives were totally shot when they were fine. All of your rider mower and larger hydrostatic drives (that I've seen) have a bypass mechanism that you manually actuate to purge air from the system. I *believe* pulling the bypass rod allows only for the pump to pump, while nothing gets to the motor end. You work the forward/reverse a cpl times and they are purged. That is a cool little hydro. Honda is clever with this stuff.

2016 Subaru Forester 2.5, CVT. 2016 Nissan Quest SV (Babe magnet IV)

#2170582 - 02/14/11 06:30 AM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: JTK]
YZ250 Offline

Registered: 02/13/11
Posts: 4
Loc: Germany
Hey FMF,

Great job!!

I'm from Germany and I've the same thinking as you. I bought a 10 years old honda-mower with the same tranny as you. Mine still works. But my experience with engines and trannys says: A service must be done after 10 years. But when asking at the dealers. Everybody said: life-long-filling, no changing. Don't open it.

So I searched the NET and found your job. I think I start the next days with my tranny. In Germany they want me to pay 45Euros for 1000ccm Honda-Hydrostatic-Fluid......Crazy!! So I take ATF-fluid. I compared yours with other brands. And I found out, that a ATF-fluid(DEXRON III) will work. Cost is only 8Euros in comparison to 45Euros... I contacted the ZF-company(trannys for example BMW-cars) and they said that ATF(Dexron III) is identical to your Redline D4 ATF.

Thanks again for your super-job

Tom from Germany

Edited by YZ250 (02/14/11 06:37 AM)

#2170709 - 02/14/11 09:30 AM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: 1 FMF]
occity79 Offline

Registered: 12/13/06
Posts: 83
Loc: maryland
Great job FMF,
Look hear>>
My HRB216 3 sp gear trans was made in France "France Reducteurs".

After 8 years I opened my gear trans up and cleaned everthing and refilled with #2 pennzoil marine grease. The factory used a gear oil. I also added a grease zerk and a grease vent to allow future greasing without the arduous teardown.

Guess we are outside the normal on our mower maintenance smile

#2172288 - 02/15/11 07:23 PM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: 1 FMF]
Superbuick96 Offline

Registered: 05/31/09
Posts: 566
Loc: Cleveland, OH
How would you rate this mower as far as the cutting features, engine power, and nexite deck? IM considerng the HRX217K2VKA which doesnt have the hydrostatic drive, but is similar otherwise.
03 Chevy Blazer 4.3 4x4 Vavoline Maxx Life FSyn 5w30
04 Ford Ranger 4.0 4x4 M1 5w30
07 Saturn Vue 3.5 AWD M1 5w20

#2174453 - 02/18/11 06:28 AM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: 1 FMF]
YZ250 Offline

Registered: 02/13/11
Posts: 4
Loc: Germany
...My Honda Hydrostatic-Fluid.....AWFUL!!!!!!!!

#2175550 - 02/19/11 12:00 PM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: YZ250]
JTK Offline

Registered: 08/14/03
Posts: 9593
Loc: Buffalo, NY
WOW! Good work.

That's what kills these small hydrostatic drives. 1) Old dirty oil. 2) Too much debris build-up on the casing causing the unit to overheat. 3) Moisture/water build-up in the oil due to getting the unit too wet.

Really your only way to know what's going on in them is to change the oil periodically.

2016 Subaru Forester 2.5, CVT. 2016 Nissan Quest SV (Babe magnet IV)

#2175579 - 02/19/11 12:34 PM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: JTK]
YZ250 Offline

Registered: 02/13/11
Posts: 4
Loc: Germany

My old hydro-oil is from a mower that was used carefully by an old man, only a few times within the last years!!! The mower is nearly new.

The only way is, to change the oil regularly. In my opinion. Every two years. O.K. it could be a little too much. But looking to the price of a new tranny......... I'll do so.

I payed 7 Dollars for 1000ccm (1Liter). This is for 4-times changing the oil.

#2176370 - 02/20/11 10:35 AM Re: honda hrx mower slow, hydrostatic fluid/oil type ? [Re: 1 FMF]
Craig in Canada Offline

Registered: 04/06/06
Posts: 1995
Loc: Toronto-ish, Canada
I've changed mine once - pretty awkward to do in my Honda Masters HR215KHXC. I also remember reading a post in another OPE forum talking about how some bolts that look like fill/drain are actually holding balls for check valves in place and if you remove them the ball might wander off to somewhere it doesn't belong inside the unit. I think the patient in that case was a Honda snowthrower with hydrostatic. Kind of scary.

I have a full service manual on the way for my unit and before mowing season hits I think I'm going to look at removing the entire hydro drive unit so that I can drain and refill on the bench instead of inverting the entire mower, making a mess, and having to deal with completely draining oil and gas.

The Masters series has a shaft input drive and not the belt configuration on the Harmony. There's a driveshaft with two universals/CVs in it which runs on top of the deck from the base of the engine into the drive with a little cover on it. It should still be pretty easy to bleed/test on the bench with a drill.

I have a liter of the Honda hydrostatic fluid from the first change before I started looking for alternates. If I was buying a fluid now I would probably look at Amsoil ATH tractor/hydraulic fluid.

Edited by Craig in Canada (02/20/11 10:35 AM)

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