Trannys in the shop, couple questions

[gshawbud]

First of all the truck is an 08 sierra 5.3 half ton and i was having issues with reverse in 4wd and 2wd, sometimes as soon as i hit the gas and sometimes it was when i was already backing up it would seem to slip out of gear with a loud clunk and you could hear what i thought was the rear diff spinning (but im just a boilermaker not a mechanic so what do i know.) I took it into gm and they tore it all apart last week and friday i called to find out what they thought and he said my front diff was in rough shape inside and would need to be replaced but that the tranny looked fine, my question is if i was only in 2wd would the front diff still somehow slip and cripple the truck like it was doing? Sorry if that doesnt make sense but like i said im no mechanic i just thought i had a basic understanding of how te drivetrain works.

 

And there was never any engine light come on it just so happened that when i took a tech out for a drive it happened right away.

[NoMoreGM4Me]

There is no connection between your front diff and the tranny when in 2wd, but there is a connection between your front wheels and the front diff. There is an electric actuator in the front diff that engages the front drive shafts and connects them to the front driveshaft.