Do you have reverse? Dodge had not changed trannys in a long time they have
updated and obviously added the overdrive but that is basically a
electronic switch. The band set up has not changed though. 1st(low) and
reverse are controled by the same band. so if 1st(low) is out or slipping
reverse will be also. You might have stretched or broke the low/reverse
band.My 95 did basically the same thing and that was the cause. I actually
replaced it with a band I had from a 78' dodge tranny. The trick was
getting the right tools to remove the plastic switches w/o breaking them.
Just in comparison I also replaced the front diff. (cause i had broken
spider gears) in my 95' with a diff. from a 74' w/same gear ratio. it
worked fine just had to adjust for backlash.
just a thought hope it helps

Ryan