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The TH400 is a heavy duty 3 speed automatic transmission used from 1967 until 1990 in GM trucks. It has been replaced by the 4L80E electronic controlled 4 speed overdrive automatic. The case is 24 1/2 inches long and has 13 bolts holding on the pan. This transmission was also used in 70s and late 60s Jeep vehicles.
The TH400 is significantly stronger than the TH350 and it should be used when strength is an issue, as it normally is in four wheeling. The disadvantage is the TH400 wastes more horsepower than the TH350, the TH350 is more efficient.
Since the TH400 is a bit longer than the 700R4 and length is normally an issue with short wheelbase Jeeps, the 700R4 may be a better swap option. The 700R4 has an overdrive which the TH400 does not have and an overdrive can make highway driving more pleasant for low geared Jeeps.
| Transmission | 1st | 2nd | 3rd | 4th | 5th | Rev |
|---|---|---|---|---|---|---|
| TH400 | 2.48 | 1.48 | 1.00 | NA |
