My brothers 94 GC 5.2L AWD is shifting out of 1st gear at very low RPMs, even with the gas pedal all the way down. If i drop the gear selector into first, it will accelerate just fine, but in drive it shifts out of 1st at very very low RPMs, this just started about a week ago. The vehicle has just over 100,000 miles on it, has never seen any heavy duty useage. Transmission Fluid seems to be just fine, pink, no burnt smell to it. Is the tranny going out or are there other things I can try to fix it with?