Final Drive RatioSome thought needs to go into the transmission, rear axle, and tire selection to find a combo that will work the best for you. Cruising at too low of an rpm can be just as bad as too much rpm. Ideally, a small-block should be spinning between 1,800-2,600 rpm at 65 mph. Here's a formula to help you calculate your hot rod's ratio:
mph x final drive ratio x 336 / tire diameter = rpm65 mph x (0.67 overdrive x 3.50 rear axle) x 336 / 28 = 1,829 rpm
| Gear Ratios | First | Second | Third | Overdrive |
| Turbo 350 | 2.52 | 1.52 | 1.00 | n/a |
| Turbo 400 | 2.48 | 1.48 | 1.00 | n/a |
| 200-4R | 2.74 | 1.57 | 1.00 | 0.67 |
| (additional 300-rpm reduction in lockup mode) |
| 4L60 / 4L60E | 3.06 | 1.62 | 1.00 | 0.70 |
| (additional 300-400-rpm reduction in lockup mode) |
| 4L80E | 2.48 | 1.48 | 1.00 | 0.75 |
| Dimensions | Total | Bellhousing | | | Length (A) | to Mount (B) |
| Turbo 350 (6" tail shaft) | 27 11/16 | 20 3/8 |
| Turbo 400 (short tail shaft) | 28 3/8 | 26 15/16 |
| 200-4R | 27 11/16 | 27 |
| 700-R4 / 4L60 | 30 3/4 | 22 1/2 |
| 4L60E (pre-1996) | 30 3/4 | 22 1/2 |
| 4L60E (1996-later) | 30 3/4 | 23 3/16 |
| 4L80E | 32 11/16 | 30 3/8 |