Is my Staghorn Sumac Diseased?

Hello. This lovely tree has been in my garden since I moved in some 15 years ago. The leaves and fruit seem fine but the trunk does not. Added to this I've noticed the tree is leaning. Can anyone tell me what's wrong with it please? Thanks so much.

 

Looks Ok to me - my experience with Sumac suggests that they dont last for ever, they grow too big & then the limbs split & the main truck dies, leaving space for the many many suckers to take over - heres a picture of the trunk of the big one out the front of my house when it let go:

--
That was about 3-4m tall, you can see that the trunk has the same sort of discolouration around the limb before it split. Its taken a couple of years for the replacement suckers to grow up to flowering hight.

I wouldnt worry about it too much but I would pick one of the suckers thats hopefully growing in a suitable place & let it grow on so you have a replacement ready.

 

It is big. So as a total Non gardener do I just chop the main trunks down.

 

It's leaning badly and seems unstable.