Reverse gear out!!

I have a 96monte carlo ls 3.1 and the trans was slippina few times and I added Lucas transfix to it. Now it just stopped going in reverse but all the other gears work. I was thinking about a trans flush and ew filter but Im not sure if that will solve it. Im trying to see if i can fix it withut a rebuild because if i have to rebuild the tranny il jts have to scrap it.

No reverse is internal failure, no way to fix this without a major repair.

The one possibility is to check the reverse servo from the outside. The servo cover can be removed and the servo piston and seals can be removed and inspected.

http://www.wwdsltd.com/files/4T60ReverseBandServo.jpg

It may also be possible to verify that the reverse band is holding the input drum or if the band or anchor are damaged. A line pressure test and scan should reveal whether the reverse solenoid is operating, and that the valves are complying.

You'll have to determine if the vehicle is worth the diagnostic time.