Chrysler Forum - Chrysler Enthusiast Forums - Help diagnosing P0740 & P0700 codes

I have a 01 T&C fwd 3.8 with 145k miles. The last 15k miles the CEL has been on with P0740 and P0700 set. This indicates a problem with the TCC. At freeway speeds I see the tach drop about 200 RPM indicating TCC lockup and when tapping the brake during light throttle after lock up I see the RPM go up about 200 indicating it's out of lock up. So no problem there and the tach is steady indicating no slippage.

I've changed the fluid & filter 3 times & the pan has been clean after the last 20k miles. So there are no shift problems, shake or slip that I can see or feel except for one condition.

When coasting down hill about 60 MPH the RPM drops about 500 which I think is normal. It's during this coasting & the tach registering about 15K that I see the tach jumping up and down about 200 RPM. Seems like it's going in and out of lock up when I'm coasting or at least trying to. If you weren’t looking at the tach you wouldn't know it because you can't feel it. Any ideas what's wrong?