I have 2 Massey Fergusons, a 1995 231, and a 208 2615.
I also have a small John Deer don't remember the number it is a 2004
Having a problem with the 2615, in that it doesn't lift my bush hog as high as it use to.
Just replaced the Hyd oil, but that did not help.
My MF2660HD has some things in common with your 2615 -- the age old famous Ferguson system in the main chassis and 3pt area. Of course I can't be sure why you have less lift from your 3pt but here a couple of comments that might help:
First question: how heavy is your hog ? What size?
-- I assume you have 2 levers -- one for Draft control and one for Position control. Make sure the Draft lever is all the way up (which in theory puts the Draft system out of the picture.) If Draft is partly involved the lift is adversely affected. Note: Massey sells a mechanical kit that freezes the top link attach point from having any effect on the internal housing Draft control feature. If your hog is
very heavy it MAY be triggering a little bit of unwanted "Draft control."
-- In truth the Draft control lever being all the way up
does not 100% remove the Draft control feature (which selectively defeats the 3 pt lifting. That is only useful if you are plowing essentially.) The Draft lever being all the way UP
only desensitizes the Draft feature, not totally locking it out. Thus a very heavy 3pt load inadvertently drags you into partial Draft control, thus defeating lift. Many if not most Massey users are not plowing fields, at least not often. That is why Massey sells the Draft bypass kit. Around $130 from your dealer or you could make one.
-- I use a 7ft 1460lb Bush hog on my larger 2660 and brand new out of the box the tractor was sometimes lifting it easily and sometimes not. After literally 2 or 3 years (and another much longer story) I discovered what the problem was and bought the Draft bypass kit. You will find maybe 10% of the dealers know this and almost none explain it to the customers.
-- I will not insult your tractor savvy by saying much about the top link length adjustment and which hole you have it in ... you might want to re-look at that and wonder if that has changed during ownership. Maybe try one of the other top link attachment holes on the beam at the back of the tractor.
-- I believe you have a separate (internal to the chassis) hyd pump for your 3pt lift. Unless you have some huge number of hours on the machine I doubt seriously that any of that is the problem.
I'm very interested to hear "the rest of the story" so let us know the eventual outcome, please. And of course WELCOME to this TBN outfit !