Back in the 40s my uncle had a almost new 41 Ford PU. Going down the street at 4 MPH as he turn on the side street give it full throttle when we crossed the next street we were at 44 MPH smooth all the way. On that same street my 39 pulls Smooth all way but I have not got it down to 4 mph without it bucking about 5.5 if I get down around 5 it starts bucking. Bubba in Texas