The Ford Barn

30 Closed Cab PU · 09-25-2018, 09:03 AM

Have been looking at what max speeds are safe for the motor.

Found info on the Barn and other places on the Internet.

Everyone seems to agree 2200rpm is max, due to lubrication issues above that rpm.

I have the 4.1 rear end in my truck, 16 inch wheels but the tire circumference seems to be the same as the 19s The speedometer is spot on/correct at 40mph. Measured at one of the speed indicators sometimes put at the side of the road.

Some say 50 is max, some say 45 is max, some say 40 is max. Which is correct?

If I want to convert to 3.78, is it a simple diff gear swap, or do axels have to also be changed? Would I experience a noticeable loss of power and acceleration?

Am considering this, most in clubs prefer to cruise at 45-50. May change if changing is not a major expense like when putting in an overdrive.

09-25-2018, 09:03 AM	#1
30 Closed Cab PU Senior Member Join Date: Aug 2018 Posts: 2,332	30 PU max safe driving speed Have been looking at what max speeds are safe for the motor. Found info on the Barn and other places on the Internet. Everyone seems to agree 2200rpm is max, due to lubrication issues above that rpm. I have the 4.1 rear end in my truck, 16 inch wheels but the tire circumference seems to be the same as the 19s The speedometer is spot on/correct at 40mph. Measured at one of the speed indicators sometimes put at the side of the road. Some say 50 is max, some say 45 is max, some say 40 is max. Which is correct? If I want to convert to 3.78, is it a simple diff gear swap, or do axels have to also be changed? Would I experience a noticeable loss of power and acceleration? Am considering this, most in clubs prefer to cruise at 45-50. May change if changing is not a major expense like when putting in an overdrive.