300e jumps out of gear too fast

[mike690003]

Hello board, I have a concern with my 1987 300e transmission.The tranny was rebuilt by the dealer four years ago, I downshifts great in highway traffic and it shifts smoothly.What concernes me is that I was pulling out from a stop sign to merge into in to heavy traffic. I stomp my gas to merge and the tranny starts to accelerate and then flattens out, as if going into a higher gear. This almost cost me the rear of my car, luckily the driver slowed down. Well I know these cars arent speed demons, but my sisters' ford focus cand pull into traffic quicker than my 300e. I lubricated my cables but that only helped a little. Could there be a problem with my bowden cable??Is it a DIY thing? Help