Posted by Keith in Washington [172.69.23.60] on Sunday, April 11, 2021 at 11:32:30 :
In Reply to: Cummins 4BT posted by Pat Holscher [172.68.37.15] on Sunday, April 11, 2021 at 10:45:11 :
The 4BT is a great engine. Many people use it to swap into Jeeps and trucks.
Will it travel at 75? That depends on the gear ratios. You must have an overdrive transmission without question. Then the axle ratio must also be correct. What you need to do is use one of the many rpm speed calculators out there. Put in 1800 rpm with a .75 ratio for the transmission and the tire’s diameter and calculate the axle ratio to keep the engine rpms about 1800. I bet you will need an axle ratio near 3.0.
You need to keep the rpms lower than 2000 rpms 1800 is better.
It the truck has front drum brakes get rid of them and swap in an axle with disk brakes.