I have a '68 RS/SS with a 350 engine and TH300 trans. that exhibits the following problem:
On a cold engine start I get an idle around 800 rpm (this seems low as I think the warm idle spec is 600). The car drives and shifts through its gears fine and I get a steady idle through P,R,N,D,2,1. However once the engine & trans reach operating temp the car drives/shifts fine with a 700 rpm idle in P,R,N but in the drive gears I get a 1200 rpm idle which is putting enough torque on the wheels that you really have to stand on the brakes to keep the car from moving.
The previous owner put a new torque coverter on the car about 9 months ago...
I am struggling with where to start looking between (1) the "low" cold engine idle, (2) the increase in rpms when putting the car in gear, and (3) 1200 rpm translating into enough torque to really move the car.
If anyone has any suggestions on where to start, I would greatly appreciate them.
Thanks.
-John