transmission whines loudly in 1st gear and reverse, will not move in reverse. on 1999 GMC Yukon Denali

will move in 1st and then runs fine and sounds fine after shifts to 2nd. what are possible causes and likely fixes.

Asked by for the 1999 GMC Yukon Denali
Lo/reverse clutch worn, internal fluid leak in clutch apply circuit, let a trans. tech check it out but prob. no easy or external fix, worth a look though. Good luck!
Good start point. I had no clue. Thank You for the info.
There are a couple of tricks that might work but you need a transmission mechanic to check it not a trans. chain store.
Most places just want to swap it out, may need that but it is worth a look first!
Thanks again. I know an independent trans. mech. that can look at it next week.
Let us know what you find out and good luck with it!