I was never able to post my Excel Spreadsheet for usable torque to the ground on this forum (maybe one is limited in file size if you do not pay ?) Anyway over on the GMC Club forum I was able to post up the spreadsheets in a PDF format. So all you guys have to do is click here, go to post #6 and post #7 and you can see information on how fast different height tires run with different transmissions and rear axle ratios.
Torque within a usable range of speeds is what I call it and you need to keep in mind these things:
1. look up the torque values which currently match your trucks set up. Now you have some idea how the ft/lbs of torque feel and at what rpm your truck now runs.
2. Compare that given number with the torque value that corresponds to the changes you are about to make. (If you are changing from 4:10 to 3:73 and then a 700r4 you can see how your vehicle is going to perform before making the change)
3. Keep in mind that one should use 460 ft/lbs of torque to the ground as a minimum (my trucks torque with 700r4, 3:73, tbi350 200hp, 30" tire diameter.) It is not a race truck but it is a nice cruiser ( 68mph 2000rpm)
Here is the link, if you have questions Pm me here on this board....Kieth
posts #6 & #7 tire diameter is shown in file name.....
http://6066gmcclub.com/forum/showthread.php?t=48090