John Deere 3720 Mower deck

[Forrest1357]

I just get one issue fixed and I run into another. I have a John Deere 3720 and just put my mid mount mower deck on. When I raise it up it immediately starts to lower on its own. It does not show this in troubleshooting in the manual so I am hoping someone can lend some advise as to what to look at.

 

[KB9UDE]

If you are using the 3rd SCV on rear of the tractor to raise the deck make sure the T bolt on top of the valve is screwed all the way down.

John

 

[Forrest1357]

That was the 1st thing I checked. It's closed tight. I've never had this happen unless that was open.

 

[mfreund]

??disconnect and reconnect the quick couplers.

 

[Oldtink]

Forrest1357, If your's is like my 3520 mid mount, the lift cylinder only has oil to one side and it will drift down by nature of the design. The recommended procedure is to use the mechanical height adjusting link on the left side of the tractor to hold the deck up for transport.

 

[BigMike50]

This is completely normal. Every 3x20 tractor with mid mount mower does this. Mine takes about 10 minutes to bleed out to the setting I have the adjustment at which is about 3 inches or so. There is no fix for it. If I keep the deck on while doing loader work, I lock mine in the highest position with deck adjustment. This topic has popped out a few times over the years. I have mine plumbed at the loader ports and disconnect the line when I need to but still lowers anyhow. Not a big deal imo. especially since its pretty easy to just lock it up when using loader. Has something to do with the way the cylinder works with one hydraulic line so I read. but I don't know for sure. However, if it is lowering to the point where you can watch it lower on its own and drops all the way down in a minute then yeah, you might want to take it in.

 

[CinderSchnauzer]

On both my previous O/S 3320 and now on CAB 3320 the mower deck raises and lowers using the rear 3rd SCV. As best as I can recall there is no leak down of the mower deck as long as the engine is running, certainly not immediately. When parked, engine off, for storage, if I forget to lower the deck - yes it will eventually leak down.

 

[sunnyside360]

On both my previous O/S 3320 and now on CAB 3320 the mower deck raises and lowers using the rear 3rd SCV. As best as I can recall there is no leak down of the mower deck as long as the engine is running, certainly not immediately. When parked, engine off, for storage, if I forget to lower the deck - yes it will eventually leak down.

My 2007 3720 cab tractor with 7-Iron 72" mmm works exactly like CinderSchnauzer's.

 

[CinderSchnauzer]

I was driving around / stopped over a period of about 4 hours yesterday with a bucket full of mulch I was spreading around. Short drive time to different spots and then stopped while working. The MMM stayed up all the time with no leak down. As before, if the tractor is parked for days and I forgot to lower the deck, yes there is leak down, but nothing immediate.

Sounds like something is wrong if you get immediate leak down.

 

[Forrest1357]

It definitely is immediate leak down and with the motor running. I have never had this in three years. I will try everything that was offered up by you guys and give er a go..