Need Help...Front Differential Questions

Troops2990 · February 24, 2012

I have an 08 GMC Sierra 1500 4x4 and am attempting to change the oil in my front differential and have a few questions..

First question: I just wanted to confirm that the bolt circled in the first picture is in fact the fill bolt that I would remove to put the new oil in? Just wondering since it is in there pretty good and I don't want to remove the wrong bolt.

Second question: When looking at what I assume to be the fill bolt on the differential, there is a rubber tube right above it, going into the diff (arrow pointing to tube in photo). Does anybody know what this tube is for??

Third question: The circled object in my third photo is the top of the tube in quesions #2, it comes out right by the mount for my second battery and looks like it has a cap on it. I am assuming that since the tube is capped, it is not a vent tube. Instead of screwing around trying to get the fill bolt out, could I pour the new oil down this tube into the differential??

Thanks for helping me out.

savillian · February 24, 2012

To be honest I have not looked at the front diff on the new trucks, but that bolt seems awfully big for a fill bolt. Perhaps one of the other guys can chime in on this?

As for the tube, that is your vent. The "cap" on it is just to ensure dust doesn't get into it.....It would take a crap load of time to get the fluid down that tube! Haha

EDIT: According to this forums post (http://www.gmfullsize.com/forum/showthread.php?t=239190) that big one is the fill! Learn something new everyday!

ujtruck · February 24, 2012

1. yes that is where you put new oil

2. yes it is your vent tube

3. yes that's your vent tube cap

Troops2990 · February 24, 2012

1. yes that is where you put new oil
2. yes it is your vent tube

3. yes that's your vent tube cap

Ha thanks, so just wrench on the fill bolt till it gives, eh?

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ujtruck · February 24, 2012

yeah, it could be very tight, I used a cheater pipe on mine, it will come loose. ooh do not DRAIN - be sure to crack the fill bolt 1st,

Troops2990 · February 24, 2012

Yeah I haven't even tried the drain plug yet since the fill plug is being a pain, tried a breaker bar today and it would just flex until the end of the bar hit the floor..probably try an impact someday here and that should do it. I also didn't want to crank too hard until I was 100% sure that was the fill plug and not something else. Thanks for your help

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