Depends on the modem.
If it's a 2wire, you can try »
gateway.2wire.netIf its a speedtouch, you can get DMT (search forum)
Google your model and you should be able to find the user interface URL.
I know our line was recently toast, had to get bell to string up a new one from the street.
Our sync was a solid 5056/800 with ~35 attenuation.
Couple weeks back, atten jumped to 45+ and sync rate was all over the place and frequent disconnects.
If your line is similarly affected, but not as bad, you'll see a slower sync rate, but not necessarily disconnects. Phone will probably also have audible buzzing/crackling/etc if there's something wrong (as suspected, since you said you got 4500 up until now)