i recently bought a 1990 deville the trany was working just fine till the other day when you shifted it to reverse it would do nothing after moving shifter back and forth it would go in to gear now it seam as though it is in gear but nothing goes , any ideas trany does not slip goes just fine but is hard to find gears

I would check the shift cable retainer. It bolts to the transaxle and is adjustable by releasing the plastic retainer, putting the trans shifter arm in park then resecuring the retainer. I'm thinking the retainer is not secured? broken or its loose on the transaxle. Have a transmission shop ck it. Its located on the top of the trans just below the distributor, you will see the cable if a friend moves the gear shift as you watch. The retainer releases like a metal watch band. A small screw driver inserted in a slot then popped open.