It was a nice day so I backed the car out of the garage for the first time since fall and noticed a problem--the transmission is slipping. Pulled the dipstick to check the fluid level and noticed it was low. I have drip pan under the car and there was a bit of fluid in the pan. The bigger problem I fear is that the dipstick was rusty nearly its entire length and there appears to be rust sediment in the fluid. Any thoughts?