if it's very difficult you can do in-situ soil refresh:
cut along the sides of the pot about 1.5 -2" all around, lift the soil out from the sides (that's the hardest part if you cannot move the pot/lift the tree out) by digging all around the sides bit by bit. cutting will trim the roots willy-nilly. i am assuming you can't lift the tree out - in very large heavy cement/clay pots sometimes it's not possible. - so then you just fill the sides with fresh mix. and also try to scratch some old soil off the top and add 1-2" new mix on top.
i am sure somebody will come in and say it's a sacrilege to do so. yet it's a common practice in many parts of europe, where they grow citrus/fruit in giant pots for many-many years without traditional repot.

Thank you for your reply. I will try to do some of your instructions .It is so rootbound that I cannot even scratch the soil off the top but I can add fresh and I guess I can get it out of the pot to scratch soil off the sides and add fresh We'll see..thanks!

it's easier to get it out when the rootball is very dry. but you might have roots adhering to the pot. so you need to get a long pruning saw and run along the rim of the pot deep.
rolling the pot on the side back 'n forth might help to knock it out, but might damage the foliage. perhaps, roll it up in plastic in a tube and tape closer to the trunk, but not directly to the trunk? sort of like gift-wrapped popsicle ;)?
it's messy, but may be after you knock it out - you can submerge it in a tub of water for like an hour ? it'll help to soften up the soil for removal, but then it'll be very heavy. don't know how you'll be able to lift it then.
you might be able to roll it sideways into a garbage bag and then flood it and tie it up - so the water has time to soften the soil. it's easier to pop the bag to drain then lifting it! and then you should be able to poke some soil out. conceivably it is possible to remove most of the soil, while you're watering it with a hose and poking at it.
but it might take a few hours....
but if you repotted it 6 years ago it must've been huge even then? how did you do it?
perhaps if you repost in tree forum you might get better response then here?