Reverse

My 86 Jeep Cherokee will not go into reverse untill the motor is heated up. What could cause this?

have you checked trans fluid, I am no transsmision expert, but i would start there, level..fluid condition..alot of the transmission chains will do a free external check.. :2cents:

Do you mean wont engage or dosent move when cold. Possible fluid and filter. 1st and reverse band might be able to adjust or clutches are burnt.

I have found that about 50% of all auto trans shifting problems can be cured by changing the transmission fluid and filter, along with cleaning out the inside of the pan.
This is something that should be done every year or two for preventive maintenance anyways.