Note: There was a TH375 made that shared all the internals and case of a 400, but had the output shaft of a 350!
For more indepth information on GM transmissions use this link Drivetrain Tech
For GM transmissions dimensions use this link
Dimiensions
| Transmission | 1st | 2nd | 3rd | 4th | Reverse |
| Powerglide | 1.76 | 1.00 | N/A | N/A | 1.76 |
| TH350 | 2.52 | 1.52 | 1.00 | N/A | 1.93 |
| TH400 | 2.48 | 1.48 | 1.00 | N/A | 2.00 |
| 2004R | 2.74 | 1.57 | 1.00 | 0.67 | 2.07 |
| 700R4 | 3.06 | 1.62 | 1.00 | 0.70 | 2.29 |
| 4L60E | 3.06 | 1.62 | 1.00 | 0.70 | 2.29 |
| 4L80E | 2.48 | 1.48 | 1.00 | 0.75 | 2.08 |
| Transmission | Year | 1st | 2nd | 3rd | 4th | Input | Output |
| M20 | 63-65 | 2.56 | 1.91 | 1.48 | 1.00 | 10 | 27 |
| M20 | 66-70 | 2.52 | 1.91 | 1.48 | 1.00 | 10 | 27 |
| M20 | 71-74 | 2.56 | 1.91 | 1.48 | 1.00 | 26 | 32 |
| M21 | 63-70 | 2.20 | 1.64 | 1.28 | 1.00 | 10 | 27 |
| M21 | 71-74 | 2.20 | 1.64 | 1.28 | 1.00 | 26 | 32 |
| M22 | 63-70 | 2.20 | 1.64 | 1.28 | 1.00 | 10 | 27 |
| M22 | 71-74 | 2.20 | 1.64 | 1.28 | 1.00 | 26 | 32 |
| Transmission | 1st | 2nd | 3rd | 4th | 5th |
| T-10 | 2.64 | 1.61 | 1.23 | 1.00 | N/A |
| T-10 | 2.88 | 1.74 | 1.33 | 1.00 | N/A |
| T-10 | 3.44 | 2.28 | 1.46 | 1.00 | N/A |
| T-5 | 2.95 | 1.94 | 1.34 | 1.00 | 0.63 |
| T-5 (Close Ratio) | 2.75 | 1.94 | 1.34 | 1.00 | 0.74 |
| The grooves are found on the input shaft. | # of grooves | 1st | 2nd | 3rd | 4th | Notes: |
| 0 | 2.85 | 2.02 | 1.35 | 1.00 | |
| 1 | 2.56 | 1.81 | 1.37 | 1.00 | Third gear on cluster has 25 teeth |
| 1 | 2.56 | 1.81 | 1.44 | 1.00 | Third gear on cluster has 21 teeth |
| 2 | 3.11 | 2.20 | 1.47 | 1.00 | |
| 3 | 3.50 | 2.48 | 1.65 | 1.00 | |