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Simplicity Hydrostatic Transmission fluid problem 16LTH

Posted by armstrr (My Page) on
Tue, May 19, 09 at 19:56

hi guys. i bought a 1990's 16lth a few years back. it served me well and i decided to treat it to a real good tune up. Amsoil 0-30, new filters, greased her all up etc. the manual said very little about the hydrostic transmission. basically, if it is low, fill it when cold to the full line. it also recommended changing it at 400hrs. well the mower is almost 20 years old, so i figured i would change it. the manual says to use "premium 10w30 motor oil".

i pulled the plug and to my suprise, almost 1 gallon emptied!

so here's my dilemma. i started to fill it and can only get few ounces in. the manual did say to fill slow because there is a filter screen, but i am finding that it takes 12hrs for the fluid to go through the filter. so basically i have been trying to fill the transmission for FOUR days!! well i need to cut the grass...so i figured i had about 1/2 gallon in her, so i fired it up, but the transmission won't engage. my guess is becuase there still isn't enough fluid in it. does this sound right? i really don't know how the transmission functions, but i do know hydro means water or fluid, so i'm guessing the amount of fluid is important.

any idea if there might be a problem that it is taking so long to "filter"? i am almost about to push the sceen out, but my better judgment tells me it might get lodged in a bad spot and bite me in the arse. can i assume that once there is enough 10w30 added it will work again?

thanks for your comments.


Follow-Up Postings:

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RE: Simplicity Hydrostatic Transmission fluid problem 16LTH

I don't know what transmission (specific make and model) is in your tractor. Do not destroy that screen. Is there another "plug" in the top of the trans housing, or maybe a "vent" hose connected somewhere on the top of the trans case? If there is another plug, or a vent hose, it might help to remove that plug or hose to allow air to escape from the case as the new oil tries to enter through the screen. We need to find out which transmission assembly was used in your tractor. Yes, the amount of fluid is very important............but, one gallon seems a bit much. Most hold somewhere around three quarts, but yours might require more oil. Another detail about dumping and refilling a hydrostat trans is that you might need to "purge the air" from the transmission before the trans will "drive" again. Purging is a procedure done by moving the "free wheeling" control valve. I'm just not sure of all the details involved in that procedure. See if you can clean off the transmission case and find a decal with the OEM and model/number on it. Knowing the brand might help in finding more specs and service data.


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RE: Simplicity Hydrostatic Transmission fluid problem 16LTH

thanks for the reply mownie. the mower is a 1692106. i have attached a user manual. page 35 shows what the back end of my mower looks like...they even show the tranny drain plug.

Here is a link that might be useful: owner's manual


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RE: Simplicity Hydrostatic Transmission fluid problem 16LTH

what about trying to spin the rear tires or axles (one way or the other) to try and promote the draining activity ?


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RE: Simplicity Hydrostatic Transmission fluid problem 16LTH

Sheesh! The only useful thing I gleaned from the manual was the trans oil capacity of 3.5 quarts. Do you have a Simplicity dealer near enough to you that you might visit and request info about filling and purging air? Most OEMs will provide an online "operator's" manual, some will provide an online parts list, very few will provide a free service manual.


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RE: Simplicity Hydrostatic Transmission fluid problem 16LTH

thanks guys. i did just what mownie suggested. they wanted me to locate a label on the transmission where the rear wheel drives are...no luck.

he did tell me after guessing which tranny was there that there is a vent. he told me it was to the right of the filler tube and took a 3/8" socket. it turns out i had to loosen a 17mm nut, back it off and then i could back out a plug with an 8mm socket...it wouldnt come out though, so i left it loose.

the dealer said to jack the rear end and just put it in forward then reverse to work out the air. after a couple of minutes, the wheels began to spin slowly in forward...a few minutes later in reverse as well. i kept going for a few more minutes, added more fluid (it did enter much quicker!!). i tightened up the plug and nut and cut grass for about 20 minutes. the tranny did not engage like it normally does. it would continue to move forward when in neutral. also, the top speed was about 1/2 of what it should be. i parked the mower to let it cool and just a few minutes ago found that the hydro fluid is still low. i hope adding the right amount of fluid and a little grass gutting will bring it back to how it was.

man, i'm really regretting being nice to my mower and changing the hydrostatic transmission fluid!! no wonder everyone i asked with a mower said they have never touched their hydros. my reallllllly fussy neighbour doesn't even think he can check the fluid level in his JD L145!!!

thanks. i'll report back so hopefully me experience will help others


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parts manual

as far as a parts manual...i tried to link it last night, but i must not have hit the button

Here is a link that might be useful: parts manual


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RE: Simplicity Hydrostatic Transmission fluid problem 16LTH

I've got the same problem with my Simplicity Regent. It is about 10 years old and has the Hydrostatic Tuff Torq K56A transmission SMPL P/N 1717194. I changed the transmission fluid 5 years ago with no problems. I changed it last week and had the same problem as armstrr. The steps in my manual basically say to drain the oil and fill it back up with 10W30. It is interesting that the on-line version of my manual has an extra step that says "If the transmission is excessively noisy or unresponsive, perform the purging procedure found in the Service section." Unfortunately I'm not finding the purging procedure in the Service section of either manual, so I'm going with the steps armstrr reported at this point.

One thing I believe I did different on this fluid change was I greased the rest of the tractor at the same time. This probably would have been fine, if I had not moved the foot pedal while the fluid was draining. I suspect this is how I introduced additional air into the system.

I found the vent with the 17mm nut with the 8mm plug just as armstrr described. It was behind the right rear wheel (as I sit on the tractor) on this model. This vent also had two rubber O rings. Once I removed the O rings, the plug moved in and out a little more, but still did not come all of the way out. I had forward working to some extent prior to removing the O rings, but not consistently. I finally got reverse to work a little, once the O rings were removed. I just continued to go back and forth from forward to reverse on the foot pedals. I haven't determined if it is better to hold it in one position for any particular length of time, so I change it up from a couple of seconds to 30 seconds or more in each position.

I can tell I still have more air to purge, but this method seems to be helping. I haven't put the wheel back on, so I cant speak to the speed issue that was mentioned. armstrr, did you ever get your tractor back to the way it was before the transmission fluid change? Is there anything else I should be doing?


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RE: Simplicity Hydrostatic Transmission fluid problem 16LTH

Hey guys. I do not have the particular model of Tuff Torq transmission as you. Mine is a Tuff Torq 71E. To purge mine, you have to pull out on the lever at the rear of the tractor that is used to push the tractor with it "out of gear". You then start the tractor, and alternate pushing on the forward and reverse pedals. This helps remove the air pockets.

Maybe you could try this. Seems like I found a one line description in my owner's manual on this procedure.

Good luck!


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RE: Simplicity Hydrostatic Transmission fluid problem 16LTH

hi Ootz. It has got a little better, but still not 100%. the tractor will continue to move backwards in neutral...i have to move the hydro lever up slightly into forward to "find" where it stops. my reverse speed seems to have come back to normal, but my forward is still only about 70%...makes grass cutting quite a bit longer...but not as bouncy!! i can't move the lever as far forward...even with quite a bit of force. i must be pushing it into an airpocket. I'll try what w-catcher says and put it into "manual push mode and play with the levers a bit.

please let me know if you have any luck improving things


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RE: Simplicity Hydrostatic Transmission fluid problem 16LTH

I did finally get my tractor running the way it should again. It took a lot of patience and persistence. Once I was consistently shifting between forward and reverse, I put it back together and gave it a try. I wasnt sure how fast the axle should be spinning, but while it was on the jack and the wheel was off I did note it was up to about 1 revolution per second. When I tested it with the wheels on the ground, the tractor barely moved.

I popped the wheel off and opened the vent again. This time I had more trouble getting the "O" rings out, so I left them in place. The vent still had some play and this seemed to work fine. I let the tractor run on the jack in forward for 10 minutes. The axle revolutions gradually increased to about 60 revolutions in 20 - 25 seconds. This rate didnt change after another 5 minutes, so I put it back together.

I would HIGHLY RECOMMEND checking the fluid level again at this point (especially if your test route is down hill from your work area). Since my filler cap is under the battery, and a pain to get at, I went for a "quick" test drive first. Initially, my speed was actually faster than it had been for the last five years (since the last time I changed the fluid) and the shifting was also tighter. It had been so long, I had forgotten the tractor had lost a step the last time I changed the transmission fluid.

As it turned out my fluid was now low, and I didnt make it back to the garage. Topping off the transmission fluid where the tractor now sat, wasnt quite enough to get it to move under its own power again. Thankfully I had made it up the steepest part of the lawn before it stopped completely, and I was able to push it the rest of the way back to the pavement where I could jack it up, pull the wheel, loosen the vent, and let it run for another 15 minutes.

This time I made sure to check the fluid before going any further. I would also recommend that you avoid over filling your unit. I had a bit of a mess when I popped the cap off this time.

Once I replaced most of the fluid that was now on the outside of my transmission, I tested it one more time, reassembled, and it was good. I would say the speed of the tractor is close to what it was when it left the factory and my mowing time was reduced by 25%.

Thanks for everyones help! Armstrr, I hope this gets you back to full speed!


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RE: Simplicity Hydrostatic Transmission fluid problem 16LTH

Can you say "success"? There, I knew you could. :^)


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