I have a GMC Sierra 4wd. 4l60e automatic transmission with 180k miles. When I put it in (D) drive, it makes a grinding sound for about 3 or 4 seconds then it catches into gear. It also does the same thing when I put it in (3). It does not do it in (2) or (1). It will also hesitate or studder when I slow down to turn while in (D). Checked fluid and it is fine. What could it be? Planetary gears?

 

Welcome to the forum. You need to ask your question in the Sierra section of the Forum as this is the Welcome New Members section. You will get more views over there.

 

Welcome to Chevrolet Forum, Colton Conrad,

Likely your clutch packs are going south.

BTW, what year is your vehicle? It won't matter but its best if owners put the engine and year down.

Also this is the welcome board, Its better to use the sub forums to ask a question.