Car thuds and pauses acceleration?

While driving my 98 Camaro yesterday, I noticed it made a loud repetitive thudding noise and the acceleration pauses simultaneously when it happens...my service engine light came on, and not only that, it flashes at me pretty dramatically since then...im a bit worried as the body is in excellent shape but if the transmission is going ill have to dump it..the car also has 136,000 on it...thanks for any info u can provide as far as diagnostics or possible repairs/cost...