honda hrx mower slow, hydrostatic fluid/oil type ?

no service manual exists for mine, only a note that says not servicable and a honda part number with a $300 price next to it. i'd like to see pics of yours if possible.

mine has a couple of removable plugs, which you could easily call a drain plug, but can also serve as a port to measure fluid pressure which i believe is their main purpose. but where the plugs on mine are located, you can't use them as an air bleed point because they are located well below where the fluid level has to be in the trans. In mine the thing needs to be completely full and only way to do that is fill it from the top and spin the input shaft so the pump flows fluid throughout the unit and pushes air out the top.
 
Originally Posted By: 1 FMF
no service manual exists for mine, only a note that says not servicable and a honda part number with a $300 price next to it. i'd like to see pics of yours if possible.

mine has a couple of removable plugs, which you could easily call a drain plug, but can also serve as a port to measure fluid pressure which i believe is their main purpose. but where the plugs on mine are located, you can't use them as an air bleed point because they are located well below where the fluid level has to be in the trans. In mine the thing needs to be completely full and only way to do that is fill it from the top and spin the input shaft so the pump flows fluid throughout the unit and pushes air out the top.


Honda publishes an entire "supplement" on mine, it appears. Is there a particular diagram you'd be interested in seeing? There are many pages of info. On one hand I don't mind trying to scan a post a couple of quick things. On the other I don't want to get into copyright hot water by posting too much.

Mine isn't supposed to be "full", there's a proper level set with a dipstick and the bleed port is off to the rear. It's below the fluid level but only a little runs out before you start cranking the shafts as they describe in the instructions. When you start to turn the shafts, copious bubbles and fluid come from the port.
 
Last edited:
Thanks to some of the great information on this thread, I was able to remove and repair the hydrostatic drive on my 12-yo Honda HRB215HXA lawn mower. Over the years, the drive had gotten slower and slower and the racheting mechanism in the wheels was gummed up to the point that the mower was impossible to push at any speed other than the very slow speed of the drive. Cutting my lawn had grown from a 30-min job to a 90-min job and I was contemplating getting a new mower, but decided to see if I could get it back up to speed.

After removing the drive, I was able to drain and refill with Honda's fluid and it restored the mower to full speed, or at least something close to it. The fluid that came out didn't look that bad. I think mine it was either low on fluid or had air in the drive. While there are two drain ports on the drive, I'm skeptical you could get the drive properly refilled without removing it.

I thought I'd give a few tips in case others might attempt the repair. Sorry no pictures.

Here's the basic order of dis-assembly:

1. Remove rear wheels - there are two washers each wheel.

2. Dis-assembly the one-way ratcheting mechanism on axles. This involves taking off cir-clips, shims, and a small spring/key assembly which ratchets on one-way gears. Mine were completely gummed up and preventing the wheels from properly disengaging from the axle/drive.

3. Toughest part. Remove the part of bottom housing deck lying over the drive belt between the motor axle and the main pulley on the drive. The problem here is that the securing bolts are going to be hidden behind multiple layers of dried dirt/grass and it will be hard to even see what part is removable. There are four bolts that have to come off: 2 near the blade center, one in a recess in the housing accessed from the bottom of the mower, and one up on the side of the mower below the gas tank. You'll probably have to beat on the housing with a rubber mallet to free things up enough to get the piece off. There are several steel spacer sleeves that you need to keep track of. On re-assembly, I had a bear of a time getting the spacer on the bolt that goes in the side of the mower to line up well enough to seat teh housing properly.

4. Unhook the drive belt from the main drive pulley. This is done by rotating the drive assembly against the tensioning spring to get some belt slack and then looping the belt off the pulley. With the drive belt off, it is easy to rotate the drive far enough to unhook the tensioning spring. When you re-assemble it really helps to have another person around so that one person can rotate the drive against the spring and the other can get the belt looped around the pulley.

5. Remove the right side axle bushing. To get enough play in the drive/axle assembly to get it out of the mower, you need to remove the bushing where the axle goes through the deck housing. This bushing it held in by another external circlip.

6. Remove the drive control cable. This is straightforward. First, release the jam nuts securing the cable sheath at the control cluster. With slack in the cable, you can remove the clevis pin and main pin that hooks the loop in the top of the cable with the speed lever. At the mower end, pry off the press fitting that secures the cable sheath to the bracket and release the cable barrel from the lever assembly on the drive. (Note: My cable was in poor shape so I attempted to replace the drive cable. Despite special ordering the $18 part from a mower dealer who spent a great deal of time looking up the right cable using my mower serial number from all the possible models, the part that Honda sent didn't work. It looked more/less correct, but the internal cable was about 1" longer than the one I took off and there wasn't enough adjustment latitude to get the cable to tension even with the adjustment at the limits It was also missing the two washers on the jam nuts which properly allow the jam nuts to be tightened and secure. I returned it and re-used the old cable.)

7. Remove the drive from the mower. With one axle bushing out, you can push the drive to one side far enough that the other axle end will swing free of the mower deck.

Once the drive is out of the mower, you can disassemble it completely (see earlier in this thread), but I just did a partial dis-assembly to verify how it works and look for anything obvious wrong. (The mechanism that controls the speed of the drive is fascinating.) I drained the fluid, refilled it on the bench, and exercised the drive enough to bleed it of air. No special bleeding procedure. I did get the unit as full as I could by filling it through the large opening secured with a two-bolt circular cover. You can test the unit by spinning the pulley with your hand while you advance the speed control lever. The axle should slowly turn.

When you do the re-assembly, you should tension the control cable so that you remove all the slack from the cable with the speed lever at slow and the speed control bar not pulled. If you do this, the lever on the drive should be at full-on and exercising the spring when you have the speed control full forward the the speed control bar pulled.

You absolutely need external cir-clip pliers as there are a lot of them to remove and replace. I've had bad luck with replaceable tip pliers, so I bought a set of non-replaceable tip pliers in different sizes that HF sells. The quality is pretty poor, but they did the job.

Keep track of the order of all the shims, washers, etc. and watch out for small parts falling out of assemblies. A couple sites have exploded parts diagrams and printing them out helps.

BTW, if you can't get the drive to work properly, one option would be to convert the mower to a non-self-propelled push mower. The quick/dirty way to do this is simply to pull off the ratcheting gears on the drive axle and cut the drive belt, but if you do this, you'll be dragging the weight of the useless drive around with you. It would be better to go ahead and remove the entire drive unit with the axles which would knock an easy 10-lbs off the mower and make it a lot easier to push.

You can see why nobody repairs this stuff commercially - there is no way to justify the several hours of labor involved for a mower worth a couple hundred bucks. But if you can get it working again, it is a satisfying weekend project.

- Mark
 
Mark,

Excellent write-up, but IMO you missed one very important thing that effects these mowers; Did you check for binding in the axle bushings?

Those are generally the cause of drive system issues on these mowers. The bushings bind-up to the point it puts so much drag on the system, it overheats and destroys the hydrostat.

You can try to clean them up and lube them, but the real fix is to replace them.

Joel
 
I wanted to say thanks to all the previous posters for all the info they provided. It gave me the courage to tear into a transmission on a machine I recently picked up.

It's an 11 year old HRH536-HXE (Euro/Asian equivalent of the HRC; shaft-driven hydrostatic transmission). The transmission fluid was thoroughly black when I checked via the dipstick, and I figured I didn't have much to lose by having a go at a thorough tear-down and internal clean.

I got very, very lucky. No major internal wear (save for a little polishing on the gear teeth). Bearings were in great shape; hydraulic motors/pumps had no discernable slop in the pistons (but I don't have the specs to measure against). There was a fair coating of black gunk everywhere, especially in the gearbox section.

Best thing, easily 50% more top-end speed post-overhaul. I'd hazard a guess that a fluid change would have gotten most of the way there, but I couldn't resist having a look inside
smile.gif


Some notes (mainly reiterating what others said)

- be meticulous when tearing down; there's lots of parts involved. Bagging/photos will help a lot, and doing it in a clean environment (ideally over a tray, so that you catch anything that decides to spring out)
- get new gaskets before you begin. I got lucky, but they're easy to damage when opening the cases
- you'll need to brush/polish the driveshaft, to allow sliding the oil seals in the gearbox case along it (thus allowing the gearbox case to separate). I didn't remove the roll pins from the shaft, but polishing it up to where they're located gave ample access to get everything clean
- have as many parts removed from the main body before you start cleaning in there. Parts cleaner (including aerosol parts cleaner, to blast out internal passages) worked a treat
- don't forget to remove/clean the magnet in the gearbox case (it'll be covered in gunk)
- watch out for ordering of washers etc. as you remove parts
- coat any parts that move against one another with hydraulic oil as you reassemble (e.g. pumps/pistons, bearings, gears)
- proper bleeding procedure helps vastly. Fill gradually, then remove the bleed screw, and get the speed control locked in the max position (zip-tie or whatever). 5-10 turns on the input shaft (in direction that engine drives the shaft or belt pulley), followed by 2-3 turns on the driveshaft (in direction of wheel motion), repeated until air-free oil comes out the bleed hole. I managed to achieve forcing fluid past the closed filler cap via carefully ignoring that procedure initially
smile.gif
 
update, i had to pull the hydro drive out again.
The spring on the pump lever on the outside of the drive was starting to rust and was sticking preventing me from backing up the mower with the drive lever released. Been putting up with that for last two seasons so i decided to fix it finally. Fix for this was wire brushing the rust off and replacing the pin that holds the spring on with a bent nail. Now the pump lever gets very good spring pressure to push it all the way back.
Since i had the drive out again i decided to get some honda hydrostatic fluid from a local lawn mower shop. They had it on the shelf and was only $7 which was cool.

I drained the redline d4atf i had been using for the past two seasons and it came out a darkish red, probably from being dirty. The entire time on the atf the hydro drive ran great, no problems other than the spring on the outside of the unit.
the unit only take a few onuces of oil so instead of breaking it apart i just drained it via the two plugs and through top fill port, then filled it and spun it up on the bench, drained it, and repeated.

... actually i filled the unit with delvac 15w40 oil first. I figured i'd give 15w40 a try again since everyone had claimed that was in the correct viscosity range. And i figured my failure the first time with it was because of not completely filling the unit. So on first go i spun it up on the bench many times and made sure it was full of 15w40. I also noticed a lot of air bubbles seemed to surface at the top of the unit. I installed the drive in the mower and it groaned when using it. I pulled the drive and it was still full, i topped it off again as much as i could and reinstalled. Still groaned and failed to produce consistent power to the wheels. so from this i conclude that motor oil is not a compatible fluid for this drive.

I pulled the drive and drained and refilled with hydrostatic fluid. once the 15w40 didn't work i decided to go get honda hydrostatic fluid and found it for $7 at a mower shop on the shelf.

And by the way honda hydrostatic fluid is completely clear, like mineral oil from a pharmacy or like clean water just thick.

Filled the unit up and purged, i ended getting some leaking when it was reinstalled in the mower i'm guessing i goofed the seal on the top of the drive and when i had the mower tipped on its side i lost some fluid. The drive groaned when i first tried it. So again i pulled it out and topped the thing off with about an ounce of honda hydro oil. Reinstalled and thing works fine. I may have to adjust the cable on it because i think it's a tad slower than it was, but the drive runs quiet and cool. Think i've cut the grass 3 or 4 times since and everything works fine on the honda hydrostatic fluid.

I sent a fresh sample of hydrostatic fluid to blackstone for analysis. it came back with viscosity at 100C of 15.17 cSt and was categorized as a thick hydraulic oil in the ISO-150 range, so 40C viscosity should be around 150 cSt. I didn't get it on the report and hope to get it resampled in the near future at 40C. So it would seem the honda hydrostatic drive in the hrx mower is forgiving on viscosity since the redline d4atf is 7.5cSt at 100C and only 34 cSt at 40C. My mower did fine for a few years with it. I think the problem is with motor oil and air entrapment, but i suppose it's possible i did not completely fill and purge the drive when trying the 15w40.

on a side note i have a honda hs928ta snowblower with the tracks and a hydrostatic drive. It is a different drive than in my hrx mower and i did have it apart and it's the same basic components inside only different size, and it goes forward and backward. I decided to use ATF+4 in that and when moving the unit around in the summer afterward it moved fine. So again it seems these type of hydrostatic drives are very tolerant to viscosity since the snowblower calls for honda hydrostatic fluid only which is a very high viscosity and the thing is used in winter in temperatures down to 0F and possibly lower. I never had a problem with the snow blower hydrostatic drive, but the oil in the reservoir cup was quite dark so i decided to change it along with greasing the rest of the drive train gearing.
 
Last edited:
i just got the report amended for 40C viscosity.
It came back as 86.211 cSt (399.7 SUS) for 40C.
And the 100C viscosity was 15.17 cSt (78.6 SUS 210F).
so online calculators say VI is 186.
it would seem honda hydrostatic fluid is comparable to a 10w-40 oil.
 
Last edited:
Hello 1 FMF. I know this a really old post but it is meaningful to me because I am having trouble w my hrb216hxa hydro transmission. I am trying to view your photos and can't. Any help you could provide would be greatly appreciated.
 
Super old thread here, but for those who are suspecting hydro issues, you are missing the boat if you don't first address the axle bushings like I suggested above. They corrode, bind-up heavily and put too much of a load on the drive. I've freed up a gear drive Honda mower and a hydro driven unit by disassembling and cleaning/scotchbriting the axle bushings. It's pretty straight forward once you give it a look over. Remove the rear wheels and you'll see the rest. Some sockets and snap-ring pliers are all that's needed IIRC.
 
Originally Posted By: 388llv
Thanks JFK. I will mic' them up but they feel good to me


Good call. One of the problems with this issue is, you usually don't know it's happening, because you can't really free-wheel the rear axle to see if the bushings are binding. Sometimes they'll give off a squeaking noise as a warning. The best fix is just to order a new set of bushings, and do this every 3-5yrs, depending on usage.
 
388llv - post a new thread in this forum asking for help with keywords honda hydrostatic trans and your mower type.
if it's the same type as mine, there's only 2 ways they don't work.
1) low on fluid
2) the cable that moves the lever on the trans is shot and the lever is not moving. this is what initially happened to mine, the cable frayed and stretched, had to buy a new $20 cable.
 
Wow, Bought a used HRX217 and the hydrostatic drive barely worked. Then I found this thread! Great stuff. Step by step article on how it get the hydrostatic drive out was awesome! I didn't break the gear box apart, just drained the sludge out of it and refilled it. I took the pulley off, put the pulley shaft in my drill and ran it for a bit, then drained and refilled again. I filled it through the cap on the top that is held down with the two screws. Now my HRX217 flys! Before it just barely lurched.
Thanks! DC
 
Originally Posted By: 1 FMF
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.


Why is it that these (the most important pics) are X on my screen yet I can see the other posters pics?
 
Old thread - would be great for me to have access to the pictures now, but there are no pictures in this thread. Did they get somehow removed?
 
old but good info as my bought new HRX about 15 yrs ago is still great but interested in a drive fluid change. adjusted the cable a while ago + it goes faster than i want to go @74 YO especially uphill!! i would love to see the pics that are gone due to age!!
 
Back
Top