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Posted by Clint Dixon [74.206.63.42] on Friday, February 24, 2012 at 19:26:35 :
In Reply to: Cruising speed with 5:83 gears? posted by Wayneh [68.55.55.71] on Friday, February 24, 2012 at 18:55:44 :
Welcome Wayneh.
These formulas can be found in a lot of books and probably in many places on the internet. This particular page came directly from a 1961 Dodge Truck Salesman's Manual. So, they are proven.
With that information and a few known variables from your truck, it is easy to back figure RPM, MPH, axle ratio, etc.
If the loaded radius of your tires is 16-inches, and your governor is factory set to regulate the engine RPM at a maximum of 3200, then you should be able to drive 52 MPH in 4th gear with 5.83 ratio gears installed in your 3rd members. At this speed and RPM, you will experience a lot of tire whine, fan whine, transfer case gear whine, and any number of vibrations from components long ago worn to an out-of-balance condition. The more worn out your truck is, the more it will sound like something is going to fail at this RPM and speed. Part of that is because we have become accustomed to quieter more comfortable vehicles over the past 60 years. A real truck (Power-Wagon) kind of wakes up the senses.
30 MPH sounds quite low. But that may be the speed your truck was driven for years and it is worn in to that speed. I would say 40-45 would be more typical but you may have to get used to different sounds and senses of feel.
4.89 gearing makes a Power-Wagon in reasonably good condition feel practically comfortable at 55 with 9.00x16 tires and a cruising engine speed between 3000 and 3200 RPM.
Junior
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