Mf 3080 Hilo no go

[madscientist]

On 16sp 3080 hi box fine. Trying to move from hi to lo is not successful. Tortoise light ok and tractor nudges forward slightly but not in and when select a gear no movement.
I'd expect tractor to default to low range if no power to Hilo solenoid. Any ideas before I remove gear linkage cover?

 

[Wellytrack]

It has a lock, it won’t default to low, remove power and move the stick to low and try again.

 

[madscientist]

It has a lock, it won’t default to low, remove power and move the stick to low and try again.

Just tried that. Lights change near gearstick but no drive hi or low now and stick doesn't go stiff either

 

[Wellytrack]

Just tried that. Lights change near gearstick but no drive hi or low now and stick doesn't go stiff either

Ahh right, hydraulic pressure? Is the forward\reverse shuttle correct? Still sounds electrical or hydraulic tbh. When you reapply power after switching does the stick snap out itself?

 

[madscientist]

Will try that. Fork loose on rail was my main line of thought.

 

[Nearly]

@masseybreaker

 

[masseybreaker]

have you had the side plate off where the hyd pump is ? from what you have said sounds like electric side is ok

 

[madscientist]

have you had the side plate off where the hyd pump is ? from what you have said sounds like electric side is ok

Haven't taken plates off yet. Just puzzled. Electric is doing its job I think ok when tractor is nudging in attemp to go into low. What actually keeps it in low? Spring loaded like 4wd pack so when no electric it normally is in low range?

 

[john432]

The eletric side of the high low engage one of the solenoid valves of the bank on the right side of the gearbox. That in turn puts oil pressure into a little ram that moves a selector in the gearbox to select high or low range. The oil seals do give up and it's a splitting job to replace.

 

[madscientist]

The eletric side of the high low engage one of the solenoid valves of the bank on the right side of the gearbox. That in turn puts oil pressure into a little ram that moves a selector in the gearbox to select high or low range. The oil seals do give up and it's a splitting job to replace.

Yes that all makes sense. But my question now is what normally keeps the ram pushed in low. Beville springs like say mf 6150 clutch, an accumulator like the vicon sower or does the low pressure circuit hold the ram in low till the solenoid tells it to move into high? Either the ram or fork is in no man's land when asked for low. The workshop manual doesn't remark this detail

 

[masseybreaker]

its the bottom solanoid just swop that for another they do bend somehow and jam. all that works the hi low is a ram on the selector rail that move the fork on the syncro ring some have a full syncro some have a slip ring. worst case is the back shaft has a bearing on the end that runs inside the front shaft they collapse and let the back shaft run at a angle stopping the hi low changing !!!! major surgery both shafts bol-ocks etc

 

[madscientist]

its the bottom solanoid just swop that for another they do bend somehow and jam. all that works the hi low is a ram on the selector rail that move the fork on the syncro ring some have a full syncro some have a slip ring. worst case is the back shaft has a bearing on the end that runs inside the front shaft they collapse and let the back shaft run at a angle stopping the hi low changing !!!! major surgery both shafts bol-ocks etc

Oh dear. Could swap over a complete valve. But if tractor is nudging back or forward when I change to lo range it's looking like something is preventing proper travel. Thanks