Posted by Keith in Washington [108.162.245.109] on Saturday, June 29, 2019 at 15:51:56 :
In Reply to: WC-62/63 4BT 5:83, 4.89, 4.30? posted by Scott [172.69.170.73] on Friday, June 28, 2019 at 19:49:40 :
For what it’s worth. I am running 9.00 X16 Michelin XLs (36+”) with 4.89 gears in 4th gear (1:1 ratio) my engine is turning 3000 RPM at 60 MPH. 3500 RPM at 70 MPH. That is on the high side for a 4BT in terms of RPM. It’s fine for a V8. You will need an overdrive of some sort.
The numbers above are for your information of real world numbers. You can change gear ratios, tire size or an overdrive and calculate on the above numbers what your engine RPM at speed will be. The calculated numbers should be fairly close.
I have talked with several who have stated that their trucks have the same RPMs with the same setup. I have talked to one individual who bought a Carryall with the same tires and gear ratios with a diesel and never could get it to road speed because of the RPM limitations of the diesel. He actually got the dealer he bought it from to take it back as it was advertised as being freeway capable. It was not. He could not get it up over 50 mph. (That particular truck has been sold multiple times over the last several years. I suspect for lack of speed.)