00 sonomia 4x4 broken in the the front

hi
does anyone have a breakdown picture of the 4x4 differential and what normally brakes.. my sister hit the button while driving and i guess went into gear and was a bang..

now she don't work.. the front drive shaft works it spins but there is no driving of the front.. what would typically brake? and how can i fix it

Often the split gear and associated fork that engages with the shot pin. Disengaging at speed is usually safe, but engaging over a few MPH is risky, especially under power.

http://farm8.staticflickr.com/7231/13178847645_c6b44ae166_b.jpg

what is a shot pin? so what your holding there is what usually brakes.. and are those expensive parts? is there a way for me to test if that's working so then whatever the front shaft that turns the gears isn't broken then like it looks like some big box the front drive shaft goes into like a massive gear so that wouldn't break...

so you always have to put the truck in neutral to get it into gear right? and if i can test this if its broken or not without taking it apart how can i test it... and whats the procedure to take this apart?

i was googling and such and i found this link
https://blazerforum.com/forum/engine-transmission-35/can-anyone-help-97-jimmy-4x4-4-3l-oil-pan-74609/

now my question is your pic it seems it would slide over gear and the right wheel would get power... but if that didn't work the Left side should always spin no matter what as it differential housing number 35 right... so if that fork doesn't enage. the right side should always spin if the front drive shaft is in gear and turning right?? and since it isn't turning

would that mean that differential housing is broken?

If the front driveshaft is engaged and only the left is connected, the differential gears will allow it to spin freely, just like a rear axle without a locker when one wheel is off the ground. That is how and why the system works.

The pin is item 17 in the breakdown in the parts diagram in your link.

The actuator cable and cable housing can be removed to inspect the pin and get a peek at the connector spline.

so i kinda understand .. but if the front differential is engaged..it looks like the left automatically turns no matter if the fork thing is engaged is that true

or the fork has to be engaged to activate the 2 front wheels

cuz what i did was lift all 4 wheels off the ground i put in neutral and put in 4x4 ad then into gear rear wheels turned the front shaft turned but neither left or right wheel turned on front and i was sure from those diagram the left will always turn...
do those gears ever break in there?

so ur sure then its probably fork..so how do i test it you said i can pull off and peek at the pin.. how do i do that you have any pics would help never done a job like this
i appreciate the help so far

and merry christmas

An open differential is a triangle of rotating shafts. Hold any one and the other 2 turn. When not properly engaged the "free" shaft turns because it has the least resistance.

It isn't the fork or pin that breaks often, but the sliding splined coupler or its associated gears. You may not know until it is opened and inspected. Watch out for gear oil leakage out the side when you open it.

This might make it a little clearer:

https://www.youtube.com/watch?v=ZtC52KShPR0

If you find a damaged gear, there is a parts kit available to repair it - Dorman 600-561.

ah ok but still kinda confused... i did watch video least i know what i gotta take apart to get it out... so that coloar does the transfer... now that one shaft is always spinning then. is that not associalted to the driver side wheel...
like i was saying if the front shaft spinning when in 4x4 that driver side should be engaged no matter what right? the sliding color only engages the right side as that shaft spinning and u slide it over...

if i wrong then i need a better video that explains
as i thinking the gears are broken that the front drive shaft powers those gears as it should automatically power the left wheel as it turns no matter if the fork is engaged or not..
least that's how i think it should work
it will have to be after new years when i can take it apart then or test that fork thing