why new style acuator?

my friend had a 89 k1500 and when i had gotten him a new acuator for the 4wd they handed me one and i called him to make sure it was the right one and the one they handed me was a 2 wire, and then when i went back in the guy mentioned something about a new style they switched to(5wire). now my friends front diff was shot we found out and so we replaced it with one from a 1990 truck he got with his truck when he bought it and it had an acuator on it that is the 2wire one.

my question is why did chevy switch to the new 5wire and what are all of the wires for cause we are currently using the 2wire one out of the 1990 diff. ? so we have extra wires hanging

I believe the older ('89-'90) front actuators were thermal 2 wire which required voltage to heat them up to engage.

The newer ones are solenoid driven. My '98 manual shows only 4 wires to the front actuator, so I don't know were your 5th wire is going.

? is does it work ok for you or not?

As 77stichman said the older one was thermal controlled and required a warm up time to kick in.
The newer plastic style gives a faster instant kick in.
Like a quick on the draw for the 4 wheel.
But requires a wiring change over to change the older one to newer one.

ok thanks guys i will see if he wants the switch over or not, it works fine with the 2 wire so far.

Something you might want to consider, as I see you live in Wisconsin is that if he is planning on driving it during the winter the old one may or maynot engage due to the cold weather. As posted in other threads on this forum.