I have a 2005 jeep grand cherokee 4X4 and when doing a routine oil change was told i needed my front and back differential changed and it looked like it had never been done. (I bought it used). I called dealership and they said that the transfercase needed done as well and it needed synthetic in it and it would cost $300. Should i have this done at dealership or somewhere cheaper, and also do u think my transmission could already be damaged from the fluid never being changed i have 75,000 miles on it. HELP!!!!!!!!!