42RLE transmission failure

[Libertynoob]

I have an 05 Jeep Liberty 4X2, w/ an automatic transmission which failed. Its a 42RLE 3 connector (LH) side part#P52850697AA. Why cant I use the what seems to be the more common 4 connector (LH) side version outside of the stated obvious connector locations difference. Is there mechanical or electrical difference in the 2 trannys?

Can anyone shed a little light on this..or direct to the forum link if any that may already have addressed this.?

Thanks