The overdrive in my transmission started to slip every now and then. I have a Dodge 2002 Full size van 2500. Can the overdrive be rebuilt? Or the whole transmission needs to be rebuilt?
Thanks in advance for your suggestions!

With proper diagnosis, only the particular pieces that have failed will need replacement.
Many transmission techs will identify the failed components and make recommendations based upon part prices and rebuild kit contents. Clear? I know... I didn't think so...

If the parts you need are only available in an overhaul kit, you may actually be charged for that kit, yet only the individual pieces that are needed to affect the repair will be installed. Why replace parts that aren't needed? Because replacing parts that haven't failed with parts that are untested can be risky and could induce new problems.

So, no. The entire tranny need not be "rebuilt"