John Deere STX38 Drive Problem

JeffL · Jul 30, 2013

after two hours mowing in texas heat with some slope it had trouble moving forward or reverse, just creep. seemed like drive problem, engine sounded pretty normal. let it sit a couple hours and cool down, back to normal.

It"s hydro, black deck, 13 HP Kohler. Haven"t had it real long got it used. Second time i mowed with it. My first hydro mower.

rrobert · Jul 30, 2013

Ick. Check fluid level. Find the vent for the transmission, dipstick or plug on top. Use a straw or wire like a dipstick. Add fluid if necessary.

If it is the same transmission as in the link below, they are easily rebuilt by DIY. I posted an informative site in the link below.

Another option is to install used. Ebay, Craigslist.

Hydros are great when they work but expensive to replace when they break.

I replaced a mid 80s hydro pump from ebay. Shipping was the expensive part! It worked for about a week. I let it sit for over a year. I decided to fire it up but trans was bone dry. Instead of using hydro fluid in it, I put 30 wt oil in it. Why not? It was already broken. Has been working great since. Even replaced the output seal.
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rrobert · Jul 30, 2013

Also check the belt. Make sure it isn't slipping or off track.

There should be a relief lever somewhere so you can roll it around freely. Make sure that is where it should be.

JeffL · Jul 30, 2013

what fluid does JD say should go in the transmission? I have "Traveller® All Season Hydraulic Oil ISO 46" or I have "Traveller® RENEW Tractor Fluid" that i keep on hand.

i did see a tube under the seat near the battery that goes nowhere, maybe that was supposed to be the transmission filler and possibly some fluid even leaked out if the tube is not connected and i have been on some slopes. i will check for belt tension too and i know the relief lever location so will check that too.

rrobert · Jul 31, 2013

I would ask a JD dealer what fluid. I know it will probably be $10 a quart. Use a turkey baster to fill fluid. I would not risk using just any fluid in it yet.

The hose by the battery? If it is clear and 1/4" hose, it is probably the battery vent hose. The hydro vent hose will be a black 3/8" hose. Yours might have the vent directly on trans under fan covered in dry grass.

If they stop working when warm, it usually means the hydro seals/pistons are worn. You might get lucky and be low on fluid. I just checked a diagram of the stx38 black deck hydro. It does have pistons but is not the same as the link above. There is a filler plug(#2) right rear of transaxle body on top.

http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.HomePageServlet_Alt

interior of trans

rrobert · Jul 31, 2013

Correction. I think the pic above is your transmission. The main JD link I posted is hard to find what you are looking for but has great info once you figure out how to use it.

The vent appears to be assembly 9 in the diagram.

The link for DIY rebuilding the hydro does not look like your transmission.

rrobert · Jul 31, 2013

Also, make sure the fan blades are not broken. Important to keep hydro pumps cool.

middleton669 · Jul 31, 2013

I have one of these, bought new in 1996. It uses 30wt. motor oil in tans. Had to change out the shaft and pulley due to splines being striped out.

JeffL · Jul 31, 2013

that is the right drawing, i found the filler cap, really dirty and hard to get to so going to need washing before i can open it. wondering if i should try to drain it and refill. the original owner never greased the front steering so i bet he never changed or checked the hydro.

rrobert · Jul 31, 2013

Honestly, I would top it off first to see if it improves performance. Get more miles out of it and then change it next year.

If you use the fluid JD sells you, it will be very expensive to change the fluid and then find out the hrydro pistons were worn.

Don't tell my mechanic friends. I have never changed the transmission fluid on my 2003 F150, 140k miles. Have had it since new. Shifts fine. I had to top fluid off once because the dipstick tube rusted and broke off the bracket. Would leak when I turned corners. I welded it back together and has been fine since.

JeffL · Aug 4, 2013

same problem after mowing about 30 minutes looses ability to go uphill.
cleaned the entire trans-axle outside and topped off with SAE30. Checked belt tension and relief lever and cooling fan.
looks like the trans-axle is dying and I don"t see rebuilt ones available online. not sure it is worth buying a new trans-axle. maybe what i need is to give up and buy a bigger tractor for mowing.

John Deere STX38 Drive Problem

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