TKO Upgrade

[xb-60]

Originally Posted by MaSnaka

....currently have a close ratio 4 speed toploader (works fantastic), rear end ratio is a 3.70 9", w/ Tru Track, mild cam.....

John,
If you stay with the 3.7 rear and change from a CR Toploader to a TKO600, the first gear ratios for the two gearboxes are very different. You would probably notice a massive difference in first gear capabilities. That may not be what you want.
Cheers,
Glen

[1795]

Unfortunately there is give and take in everything. If you go with the TKO the overdrive should be in a range that you will use on a regular basis. The .82 will allow you to get into overdrive at a lower speed, with the .64 you will not be able to functionally use it until 65-70 and the lower gearing in 1st and second may not be what you want. If you change the rear end you would have to drop considerably, my top loader with a 3.54 rear end runs about 2800 rpm at 60 and 3200 rpm at 75. The trade off is that with a ratio in the 3.23 range you are going to have trouble getting into 4th gear until about 50.

What you have to decide is the typical driving that you do and what level of performance you are looking for. I have thought about getting a .82 overdrive for my car so that it would improve long range mpg and be a little quieter down the road. However, for the most part I am driving in the 60-65 mph ranger on country roads and that puts me at the beginning of the power range of my cam and the car loves it. Good luck with your decision and try to keep the cost within means.