I recently hit 160k miles on my 2003 nissan frontier XE v6 3.3L RWD automatic transmission. I park on the street which faces uphill. When I start the truck and shift into drive and press the gas pedal the truck will roll backward 3 or 4 feet before it Jerks and drives forward. I also notice after accelerating sometimes I can hear a grinding noise coming from the rear of the truck that lasts for a second and stops. I'm trying to figure out if it's the transfer case or torque converter. Any ideas?