NWR: GMC TRUCK PAYMENT...?

Does anyone know what the payment website is to pay a truck payment through GMC....We were suppose to get the payment booklet and never recieved it and I just realized that FH's truck payment is due in 2 days and I can't find a website anywhere...
TIA

I don't have a GMC but is this the same company you have the car loan through???

http://www.gmacfs.com/us/en/personal/automotive/


I could be way off on this but it doesn't hurt to check.