I have not been able to find any other posts about this problem. I have an 84 Fiero with the 4 speed manual 4 cylinder. The trans mission shifts fine 1 through 4 but when I get it into reverse it will not stay. It slides sideways directly in first if I let go. This is my second 84 and I don't remember having to hold it in reverse. I have replaced both shifting cables and cleaned the shifter. Is there anything else to try or should I take it to a shop. I did my best to adjust it but any tips would be appreciated. Thanks. If there is already a post on this problem can you give me a link to it.

Can you disconnect the shift cables and select reverse at the transmission directly. Then start and release clutch....If it holds, then it's the cable synchronization,
Does it hold while engine off vs running?

Eureka!!!! Found the problem. The Notched "L" bracket that works as the reverse lockout on the shifter was out of adjustment. It was not completely making it over the roller bearing and was kicking it back into first when I released the shifter. Thanks for your help. Hope this can help someone down the road.