97 Tahoe, only reverse L1 is reverse?

[92GMC]

Had a guy call me today to come look at his 97 Tahoe. He was mudding ad lost all forward gears. I went to look at it, fired it up, reverse works perfect. Put on drive nothing, pull down to L1 and it goes in to reverse. Linkage is working as it should. Any suggestions?

 

[twomanymontes]

I believe First and reverse are the same gears, but the planetary gears spin in different ways. I sounds like the planetary gear or the sun gear is broken. Either way it's an internal failure and the trans will need to be rebuilt