Yes, it is possible, but not practical in my opinion.
The job is a major redesign of the drive train.
- Both drivelines have to be modified
- The crossmember support position has to be changed
- There’s the cost of the 350/400 transmission to purchase for the swap
- The filler tube/dipstick has to be changed
- The adapter to the transfer unit for the 700 will not fit the 400, it will for the 350
- The output shaft of the 400 will be expensive since 700 output shaft has a smaller diameter, and the 350 will need a different length shaft
- An electrical kickdown switch has to be installed for the 400
- The throttle valve cable will have to be replaced with a kickdown cable for the 350
Also the gear ratios are different for 1st, 2nd, and reverse, so the takeoff will be less efficient.
| 350 / 400 | 700 | |
| 1st gear | 2.48 : 1 | 3.06 : 1 |
| 2nd gear | 1.48 : 1 | 1.62 : 1 |
| 3rd gear | 1 : 1 | 1 : 1 |
| Overdrive | none | 1 : 1.30 |
| Reverse | 1.93 : 1 | 2.29 : 1 |
With no overdrive, the engine rpm’s will be higher at highway speeds (same as 3rd gear with the 700) and the gas mileage will be less.
In late model, computer controlled applications, the electrical system will need to be modified since the normal feedback to the computer will not be available with the 350/400.
Other than that, the 350/400 are good units, but the 700 can be built to hold up.
