I forgot to mention . . .
With the chart information I gave you, there were additional comments.
If you desire the 3.33 drive ratio (which many do),
and you plan to have the 4T60 rebuilt. If the final drive ratio of the TH125C you're replacing is 3.33, there is another solution. GM liked to reuse parts whenever possible to reduce costs. In designing the 4T60, the final drive of the earlier TH125C was reused. The final drive and sun gear from the TH125C will work in the 4T60. The ring gears of the two transmissions are different and will not interchange. This is not a problem however since the planetary gears will fit either ring gear unit. Keep the 4T60 ring gear and when rebuilding, assemble it with the TH125C sun gear and final drive.
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Marc in sunny Titusville, FL
- 84 SE son's car, loaded
- 85 Coup w/V6 transplant
- 85 GT newly on the road
- 86 SE/GT "The Chameleon" - big plans!
