My 1975 164e has developed some transmission slippage, particularly on hard acceleration from a stop. In this case it will slip pretty badly causing the car to jerk a few times before accelerating normally. I have also noticed uneven performance between about 25 and 35 mph, where there may be some brief and intermittent slippage...not enough to hear or see noticeable motor RPM change, but enough that the car does not drive or accelerate evenly. Most of the time, and at most speeds, the tranny seems to work just fine, shifting smoothly and downshifting on demand. Any ideas of what to look for?