2015 Front Differential Fluid = Black

[Mardimus]

My 2015 GMC Sierra 1500 Denali has close to 110k miles on it.  Last week my son and I were headed to the mountain to snowboard when we got caught in a massive snow storm on the mountain pass. Semi-trucks were getting stuck and it was a disaster.  I put the truck in auto (2W/Auto/4Hi/4Low) and continued up the mountain with no issue. Well I though it was no issue. As we were sitting there in a traffic jam as lanes merged i started to smell this weird propane smell coming into the cabin of our truck. I assumed it was all the exhaust of the trucks and semis and did not think too much of it. We made it to the mountain and ended up having a killer day. Came back to a parking lot slammed with snow. I ended up getting stuck for a moment and ended up getting out with no issue. But the smell was definitely more noticeable now and very strong.  So I opened the hood and crawled under the truck and saw no issue. I was still in auto (2W/Auto/4Hi/4Low). I drive down the mountain as far as I could and then switched to 2W (2W/Auto/4Hi/4Low) as I was afraid something wa burning up my front differential. I stopped again and could not see much as it was horribly wet out.  Continued home in 2W (2W/Auto/4Hi/4Low) and the smell eventually went away.  

I had to leave town and had no time to get under the truck. Tonight I finally found time to hop under the truck and see what was up.  I removed the belly pan and for sure I saw differential fluid all over the driver side. I pulled the top plug from the differential and could smell a horrible burnt fluid smell. I poked my finger in and sure enough it was low enough I could not feel fluid.  Pulled the lower plug and fluid came out.

It was black and grayish/metallic from what ever was grinding. Super bummed but not sure what the damage is. I did see some metal dust between 5 and 7 in the image below.  Also, you can see the dust in the pic with the Red arrow. Which leads me to believe i blew a seal of some sort. The passenger side looks fine and has no noise or issue. AACJ 3.42. Changed Fluid about a year ago when it hit around 9X,000 miles. 

My question to the forum, and I greatly appreciate any thoughts or advice.  Can I rebuild or do I replace the front differential? 

[Mardimus]

Bump for some love. 

[Black02Silverado]

You can rebuild it, especially if you enjoy doing stuff like that.  I'm sure there is a YouTube video out there, at least I would think so.  If all else fails and you plan on keeping the truck then get a new one.

 

My friend has a 2007 GMC Denali and his is all wheel drive all the time.  I changed his fluid for him when he hit 200k and the fluid looked ok but there was a lot more metal shavings on the drain plug then I would have liked. 

[davester]

I would suggest finding a used one and throw it in.  Normally the front diffs last a long time if they aren't abused (and I'm not saying you did).

 

You could also perhaps rebuild the one you take out and sell it (or reinstall it and sell the one you put in) to further reduce how much you pay.

[Mardimus]

On 1/29/2020 at 3:09 PM, Black02Silverado said:

You can rebuild it, especially if you enjoy doing stuff like that.  I'm sure there is a YouTube video out there, at least I would think so.  If all else fails and you plan on keeping the truck then get a new one.

 

My friend has a 2007 GMC Denali and his is all wheel drive all the time.  I changed his fluid for him when he hit 200k and the fluid looked ok but there was a lot more metal shavings on the drain plug then I would have liked. 

Thank you for the reply. Sorry for the late response as I was out of town. I stopped by a local transmission and differential shop and the owner of the shop pretty much said the same thing based on the pics I sent him. He agreed I could do a rebuild myself.  He thinks the gears are fine but the bearings and area where the axle connects was possibly rubbing.  He said I could pull it out and bring it in to him and it would be a lot less labor to check it out. But again he said without really looking at it in person there is not much he could recommend. I like doing these projects myself and have rebuilt quite a bit of motorcycle and small car engines. Never removed or rebuilt a differential. But it does not seem to complicated.  Is there a good site that folks on this site use to order parts or rebuild kits?  I am also looking for an exploded diagram/parts list for my 3.42 front differential. Can anyone recommend one?  If I do decide to dive into this should I look to upgrade to a 3.7 gear and would that include needing to do the rear to match (Ill google more on that).  But since I have the front diff removed, should I upgrade or add anything else?  The truck is all stock and not lifted.  Thanks for all the help.  

[Mardimus]

On 1/29/2020 at 11:15 PM, davester said:

I would suggest finding a used one and throw it in.  Normally the front diffs last a long time if they aren't abused (and I'm not saying you did).

 

You could also perhaps rebuild the one you take out and sell it (or reinstall it and sell the one you put in) to further reduce how much you pay.

I use the truck to tow a 23' malibu boat and 28' travel trailer.  But to be honest, I never really drive it as I have a daily driver.  I cant speak for the owner before me (sigh).  I am thinking I will pull it out and rebuild it or like you said replace it and then rebuild and sell the other one.  Any thoughts on a good site for rebuild kits/used ones? I have google searched around and it seems like a lot of shops dont have them in stock. Thanks for the feedback and help. Cheers. 

[davester]

If you are near/in a city of any significant size, there should be at least one used part place, you can phone them, or google used parts online, lots of places will ship them.  If you want a little cheaper, you have to go to junkyards and pull one yourself.  Either way, if you are considering changing diff ratios, get one with the right ratio, then you only have to do the rear one.

 

Transmission parts places typically will also have diff parts/kits.  Online I would try rockauto.com, and if they don't have it, google for other places.  I haven't had to search for diff parts myself.

[Black02Silverado]

Yukon Gear is one place to start for parts to rebuild.  They might even have information on how to get it done or can direct you to the right source.

 

[Mardimus]

5 hours ago, davester said:

If you are near/in a city of any significant size, there should be at least one used part place, you can phone them, or google used parts online, lots of places will ship them.  If you want a little cheaper, you have to go to junkyards and pull one yourself.  Either way, if you are considering changing diff ratios, get one with the right ratio, then you only have to do the rear one.

 

Transmission parts places typically will also have diff parts/kits.  Online I would try rockauto.com, and if they don't have it, google for other places.  I haven't had to search for diff parts myself.

Thanks for the reply. I hit up a few pick and pull places around Seattle. Added a couple alerts in case one comes in. I’ll check out a couple local shops and see what they have. Thanks again. 

[Mardimus]

1 hour ago, Black02Silverado said:

Yukon Gear is one place to start for parts to rebuild.  They might even have information on how to get it done or can direct you to the right source.

 

Checking out Yukon gear now. Thanks. 
 

update: I live less than 10 miles from Yukon Gear. I’m going to head over to their shop tomorrow. Thanks again. 

Edited February 5, 2020 by Mardimus

[Mardimus]

Quick question as I start to put together a date and time to tackle this myself. I talked to the guys at Yukon gear and they have all the parts in stock. But one issue I am running into is that my garage is not long enough to keep the trucks on jacks for multiple days. Can’t close the garage door. So my question is, can I pull the front differential and then jack the truck back down on to the wheels and roll it out into drive way with out any damage? This way I can rebuild the differential over a couple days and then bring it back it when ready to reinstall it. I don’t plan to drive it but would just roll it out and roll it back in. Looking at the axles from underneath it appears it would be fine but I wanted to make sure before hand. If this strategy doesn’t work then I’ll have to take it to my uncles shop and put it on his lift and it’s a bit of a drive to get to and from there over multiple days. Thanks again for the help. 

[JimCost2014]

5 hours ago, Mardimus said:

Quick question as I start to put together a date and time to tackle this myself. I talked to the guys at Yukon gear and they have all the parts in stock. But one issue I am running into is that my garage is not long enough to keep the trucks on jacks for multiple days. Can’t close the garage door. So my question is, can I pull the front differential and then jack the truck back down on to the wheels and roll it out into drive way with out any damage? This way I can rebuild the differential over a couple days and then bring it back it when ready to reinstall it. I don’t plan to drive it but would just roll it out and roll it back in. Looking at the axles from underneath it appears it would be fine but I wanted to make sure before hand. If this strategy doesn’t work then I’ll have to take it to my uncles shop and put it on his lift and it’s a bit of a drive to get to and from there over multiple days. Thanks again for the help. 

Off topic, what area of Seattle are you in?

[davester]

Sure, you could even drive it around.  You need to remove the cv shafts to each wheel (as they would flop around damaging themselves and all the parts around them as they rotate), and you can either tie up the front driveshaft or remove it (and remember to not switch into 4wd)...

 

Just rolling it into the driveway, you could just tie up the cv shafts (but so they can rotate) and it'll be fine.  Maybe tie up the steering wheel or somehow indicate that it should not be driven...

[Mardimus]

15 minutes ago, JimCost2014 said:

Off topic, what area of Seattle are you in?

North. Mukilteo. So not really Seattle but it’s easier to use Seattle as a landmark than the Muk. No one knows about Muk unless you live on the west side. Lol. 

[Mardimus]

9 minutes ago, davester said:

Sure, you could even drive it around.  You need to remove the cv shafts to each wheel (as they would flop around damaging themselves and all the parts around them as they rotate), and you can either tie up the front driveshaft or remove it (and remember to not switch into 4wd)...

 

Just rolling it into the driveway, you could just tie up the cv shafts (but so they can rotate) and it'll be fine.  Maybe tie up the steering wheel or somehow indicate that it should not be driven...

Thanks for the reply. Yeah I was thinking if I tied them up just loose enough so they could rotate then it would work out. Wasn’t sure about any other areas that had stress points that could cause damage. And for sure no 4wd.