5435 Massey not speedshifting

[chade1968]

My tractor will not shift when using the speedshift button. The dash light changes from C to D but the transmission does not change. The solenoid (located under the panel on the left side) is activating. It is the top solenoid so I swaped it with another but it still did not shift. It did shift once but not again.
My dad changed the 3 transmission filters he said and the fluid level is correct. Any advice on what to check will be greatly appreciated.

 

[MFRED]

How many hours on your machine? Does the high/low range shift fine? Does it not shift all the time or when hot?

 

[chade1968]

The tractor has 800 hours and it never shifts, hot or cold. It did one time the other day but that was it.