How to bleed a hydrostatic transmission on John Deere F1445 front deck mower?

[Shaun]

I have just swopped out a complete transmission from another working mower but since then I can not get the mower to drive in either direction. The PTO works, the deck lifts and lowers and the power steering works so the pump is working? I’m hoping it’s just an airlock somewhere but unable to work out how to bleed the system??? Maybe it’s something I’ve missed and open to suggestions.

Thanks.

 

[hay&hydraulics]

Hydrostatic trans require purging after you replace them. Start by lifting the rear wheels, then fire up the engine. Gradually push the drive levers all the way forward and then all the way in reverse several times while keeping the engine at half throttle. Do this around 10 to 15 times to help get rid of any air trapped in the system. Finally, make sure to check the fluid level, as it might be low after the swap

 

[Greenwrench]

Be sure to check the bypass valves again, if they’re still open from the swap, your mower won’t budge. Also, make sure that the linkages connecting to the drive control arms are properly hooked up and adjusted.

 

[Shaun]

Hydrostatic trans require purging after you replace them. Start by lifting the rear wheels, then fire up the engine. Gradually push the drive levers all the way forward and then all the way in reverse several times while keeping the engine at half throttle. Do this around 10 to 15 times to help get rid of any air trapped in the system. Finally, make sure to check the fluid level, as it might be low after the swap

I had tried that and to double check ran through the procedure agin but with no luck.

 

[Shaun]

Be sure to check the bypass valves again, if they’re still open from the swap, your mower won’t budge. Also, make sure that the linkages connecting to the drive control arms are properly hooked up and adjusted.

Where are the bypass valves and what is involved in checking these.
The linkage for the drive looks ok.
When I first started the mower the front hubs did rotate for 2-3 seconds then slow down and stop. No rotation since then?

 

[Greenwrench]

Where are the bypass valves and what is involved in checking these.
The linkage for the drive looks ok.
When I first started the mower the front hubs did rotate for 2-3 seconds then slow down and stop. No rotation since then?

Bypass valves are located on the transmission, usually marked with a lever or knob that can be turned or pushed. They're used to disengage the transmission for towing, if open, no drive power transfers.

To close them, rotate or push the bypass levers/knobs fully in or to the "closed" position. They should click or seat firmly. Check both sides if it's a dual hydro setup.

The fact your hubs rotated briefly then stopped suggests air in the system or bypass valves partially open. Close the valves completely, then jack up the front wheels and run the purging procedure: engine at half throttle, slowly cycle drive levers forward/reverse 10-15 times to work out air.

I couldn’t track down a video for the F1445 bypass valves, but this one covers a similar setup and might be useful:

 

[Shaun]

Bypass valves are located on the transmission, usually marked with a lever or knob that can be turned or pushed. They're used to disengage the transmission for towing, if open, no drive power transfers.

To close them, rotate or push the bypass levers/knobs fully in or to the "closed" position. They should click or seat firmly. Check both sides if it's a dual hydro setup.

The fact your hubs rotated briefly then stopped suggests air in the system or bypass valves partially open. Close the valves completely, then jack up the front wheels and run the purging procedure: engine at half throttle, slowly cycle drive levers forward/reverse 10-15 times to work out air.

I couldn’t track down a video for the F1445 bypass valves, but this one covers a similar setup and might be useful:

Thanks for the advice and the link. will check and see what I can find.

 

[Shaun]

Thanks for the advice and the link. will check and see what I can find.

I think I’ve worked out what is happening but need to carry out a repair to confirm.
I ran the machine and tried to bleed the system one last time with no luck. I then identified the bypass valve, removed it and the oil that came out was very aerated. I had a look over the machine to see if there any loose pipes allowing air into the system. I noticed that the sump oil pick up pipe was damp at the top and on further investigation I have found a split in a rubber tee connection. I think air is being sucked in rather than the oil being drawn up from the sump. I will swap it out with the one from the other transmission which looks in good condition.
Fingers crossed I’ll have it cracked over the weekend?