No reverse

Hi, everybody. My Lumina APV 92/93 3,1 van is not working on reverse. It seems there is no power.
Before it happens, I had problem with 2 to 3 gear. Changed all the gaskets because was leaking. Now the forwards gears are perfect. But the reverse doesn´t want work. Any idea? Thanks :attention

www.avigex.ca/xport/3T40rev.jpg

Hi, everybody. My Lumina APV 92/93 3,1 van is not working on reverse. It seems there is no power.
Before it happens, I had problem with 2 to 3 gear. Changed all the gaskets because was leaking. Now the forwards gears are perfect. But the reverse doesn´t want work. Any idea? Thanks :attention
Thank you so much for reply. Last time I needed, you helped a lot. Will show picture to mechanic and let see how things will come out. Thanks.

Debora , you said all the gaskets were changed out because it was leaking ? Did you take it in to a shop to have transmission work done or...what did it mean ? If that was the case , did the transmission work okay immediately afterward and then develop the problem later ? Or was the problem there when you got it back ? Perhaps the shift linkage was reinstalled incorrectly ? Perhaps the work was done incorrectly ? It's hard to say for sure when you can't actually see the vehicle .Sorry I can't help more .