C4 must be revved before abruptly moving forward in drive

"overfilled it according to dipstick"?... If it was actually overfilled when the dipstick marking said it was full.. then you obviously have the wrong dipstick.

Are you saying it was overfilled and draining some out fixed the problem?

 

Proper check method is hot(run at least 20-30 minutes) idling in park.

If you pull stick cold, before starting, it's going to read approx two quarts over full.

 

Yep.. pan drainback after shutdown pushes the level up past the full mark which is the entire reason the engine needs to be running to check it in the first place. On the flipside.. trans fluid volume expands with heat so if you check it running cold it will appear low on the stick and should not be filled until trans fluid reaches proper running temp.

 

Ditto, could be a deeper pan than the dipstick is marked for

 

Won't make any difference. Fluid level has to be at same point on stick for level to be correct. Eight quarts in a transmission that has a two quart deeper than stock pan would not register.

Either stick is too long or dip tube too short.

 

Right on. The correct fluid level is related to the pans mounting surface(valvebody to be specific).. not the bottom of the pan. No matter how deep it is the correct fluid level must always end up in the same place.

 

Not if you go by the book and fill with X number of quarts.

 

Irrelevant for this discussion, it's already been stated transmission was over full by dipstick reading.

 

And if he's got the wrong dipstick that too is irrelevant.

 

Not if it's the problem.