Hoozat, what is the gear ratio for 1st gear of your T-5? (They are available in different ratios.) That is a crucial consideration when running a 3.08 rear end so that the truck can get out of its own way on a hill or when hauling a load.
Carl
I'll jump in. Sorry Hoozat, if I'm stealing your answer.
The S10 T5 comes with either a 4.03 or a 3.75 first gear. The 1964-66 trucks with a column 3 speed usually had a 3.73 rear and a 2.95 first gear. So 2.95 X 3.73 = 11.00.
I've always heard that the combination of first X the rear should be somewhere between 9 and 12. So 11.00 worked great for these trucks.
So 4.03 X 3.08 = 12.41 and 3.75 X 3.08 = 11.55. Both of those results are really acceptable. Folks with the 3.73 or 3.90 rears usually feel that the S10 first gear is more like a granny gear. Having the 3.08 solves that.
Second third and fourth gears are simply incremental steps getting you up to speed.
So then fourth gear would be 1.0 X 3.08 and have lower RPMs than the factory tranny. That's good enough but the extra 5th gear sweetens the pot if you happen to have the 0.86. Fifth gear of 0.86 is what I recommend for a 3.08 rear since 0.86 X 3.08 = 2.65. The 0.72 OD gear would make a low HP truck lug. You want the OD gear X the rear end somewhere between 2.7 or 2.9 ideally.
