The Stovebolt Site Forums The Shop Area Driveline SM420 4 speed, speed.

So, it has taken awhile for me to put a tach on this truck. Assuming it was working right, the truck is turning about 2500 rpm at 40 MPH and sounds and feels like it is pushing the outer limits at that point. Things just don't add up. The engine is rated for max hp at 4200 rpm! It is entirely possible that everything is a bit off. I adjusted the valves a little while ago and now I am second guessing whether i did that properly too.

As for the clutch slipping, it does not seem to be slipping in an obvious manner but it does shudder a little bit when letting the clutch out in second.