A 3 speed with a 4.0 you say? Does is the transmission computer controlled or is it just kickdown linkage? What type of transmission is it?
I don't think that you are from the US, but here in the US, all 4.0 Comanches with an automatic transmission came with the AW4 4 speed automatic. Other AMC and Jeep models could come with 3 speed autos. In AMCs, I know this was the TF998 in the late 70s.