Passenger Output Shaft S70
 

I am new to Volvos. Just bought a used 99 S70 which runs very well. About a week ago, I started to notice slipping of the tranny, mostly after a hard stop. I took to it be checked out and found the transmission oil very low and a leakage at the output shaft in. What is additionally odd is what looks like the seal ring itself lose on the shaft. Is this safe to drive it this way? Is there other transmission damage I need to be concerned with?

After adding transmission fluid it runs fine, no slipping. I drive a lot of miles a day, I have to wait until I get paid again to fix this. Any help you can provide will be good. Thanks.