My son has an 88 Jeep Cherokee, Automatic 4X4. The reverse just went out in it. Goes in to drive OK, but nothing in reverse, I assume it's the transmission. My question is how safe is it for him to drive until he can get it fixed? I believe all the parts inside the transmission are different for reverse than they are for the forward gears so I wouldn't think there'd be much chance the rest would go out on him. Would it??

I wouldn't drive the jeep at all
Unless you are going to put a completely new transmission in it
When one thing goes bad I won't belong till they all do

I wouldn't drive the jeep at all. The more he drives it there is a possibility that he will mess up more.