I have a new to me 2001 ZR2 Blazer with a strange trans issue. The trans fluid is brown but doesn't smell burnt. I haven't pulled the pan yet to see if there's a bunch of metal and junk in the that would indicate a full on internal mechanical issue. I'm hopping it's just an issue in the valve body. Like a broken spring or a stuck valve.
Park: Is normal with no abnormal noises or load.
Reverse: Engages and rolls back for a moment and then stops. It feels like a forward clutch applies and it stops moving almost like a doing a power break. I didn't give it much throttle I didn't want to hurt it any worse.
Neutral: Acts like drive and drives forward.
D4-D1: Moves forward in all Drive positions. I did a hot lap around my house in D4 and it shifted into Second normally. I didn't go far, fast or try all the Drive positions to not cause anymore damage.

Any help would be appreciated and thanks in advance.