transmission comp. slipping
2000 gmc jimmy
any suggestions?

Classic P1870...do a search on the blazer or even this jimmy forum. Its very common. It could be a variety of things, PWM sensor, PCS solonoid, or even a worn out valve body. When was the last time you did a full tranny fluid and filter flush? Does it shift hard between gears...especially 1st to 2nd? Does the TCC lock up? Hope this helps.