Siple drain and refill, no gaskets required, plugs have magnets on them, so clean them with a rag. I found the first drain on my diffs to have a lot of material(break in) on the magnets. Last service i noticed there was much less. Use a good lube of your choice, not going to recommend brands to start a brand war,LOL.

 

Appreciate your help! Not alot on the web about these trucks for basic maintenance. Chevy definitely made it simple on this one then.

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Page 353 of my 16 Colorado CCSB. Manual has the information.

 

Loosen the fill plugs first; if you drain the fluids and then find the fill plugs frozen you are screwed.

 

This guy is absolutely correct. It's a bad feeling to find out after you drain the fluid and find out that you cannot fill it.

 

Thanks for everyone's input. Doing both the front and back, it took about 2.5 quarts. I needed an 8mm diff drain plug remover. The front was annoying, I spilled some of it trying to use a funnel extension so I just got angry and squeeze the crap out of bottle to get it in, no problems!

For an I4 4x4 without the tow package 47k miles, the rear diff was absolutely filthy. There was a half inch of metal on the drain plug with black oil. The front was fine, it probably didn't need an immediate change but it's better safe then sorry.

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I’m sounding pretty naive... are you saying you needed a special tool to remove the drain plug? I thought it would be a standard 8mm wrench.
The drain is the one w the magnet, not the full cap, correct? So you have to fully drain it to wipe off the crap from the magnet?


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You really don't need any special socket. Just use the square end of a 3/8" socket wrench extension (no socket on the end).

I use pipe sealant on the drain/fill plugs. No need to make them gorilla tight.
Easy stuff...

I was totally surprised that the capacity for the rear is only about 1.5qts. Crazy small amount of fluid.

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Yes, the process to change the Diff Oil is pretty straight forward:

• Remove fill plug, check level for reference.
• Remove drain plug, clean magnet on plug while oil drains.
• Replace drain plug, torque to requirement (I used 24 Ft-Lb for 2015 Colorado Z71)
• Fill Diff with new oil.(~1.6 qts - bottom of fill plug opening - I use small hand pump that screws onto top of bottle)
• Replace fill plug, torque to requirement. Wipe up any drips

I just changed mine last weekend (32K miles). I used Valvoline Full Synthetic, as it met the GL-5 requirement and was less expensive than the Mobile One (these were the only 2 synthetic oil my local auto parts store had in stock). I also just use the 3/8" drive on my wrench as this fits the plugs with no slip/stick or other issues.

For reference, and a different thread... I used 75W-140 weight oil to quiet the loud "slap" I would occasionally get from the Diff when the Tranny could not decide what gear it should be in. Did the trick!
:smile2:

 

Trying the 3/8 fitment on the socket wrench definitely would have been smart.. oh well, atleast it was a cheap mistake [emoji23]

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Think of it this way. Now you just have an extra socket extension, a really short socket extension.....haha

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What is the recommended service interval for the differentials? Do trucks with the G80 need a special additive, or is it pretty straight forward with the 75W90? Manual doesn't mention anything. But I figured I would ask.

 

The manual just says regular maintenance isn’t necessary, which is dumb. I would do it every 30k just to be safe. No special fluid needed for the G80 since it’s a mechanical locker and not a clutch-based limited slip.

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Here is a handy lookup guide for capacities, filters and lubes ►Lookup Guide

 

I know people like synthetics, but I'm not sure it's the best bet for differentials. On the Jeep forums, the big aftermarket diff maker did some extensive research and found that synthetics in differentials did not dissipate heat well. They saw high failure rates with synthetics and said use of synthetics in their differentials would void the warranty.
I'm not saying this will affect the GM diff or warranty, but I think the science is sound, and synthetic is probably not the best for differentials.

 

I am going to do my diff oil change in the near future and not sure of which fluid? The AC delco 88863089 that is in the manual when I look it up at Summit Racing says it has no limited slip aditive, when I look at the Mobile 1 synthetic it says that that one does. Should i stick with OEM on this since I have a mechanical Eaton locker or will it not matter?

 

EDIT: DO not use ANY fiction modifier in the G80, it can make it not want to lock and chatter.



Doesn't matter. Of course GM recommends their oil but the Mobil 1 is a GL-5 rated gear lube which is what you want. If you think about it our Eatons do have clutches. I think they are there to just kind of buffer the locker when it engages, nothing more. This is much different than the way a limited slip works so no need for the friction modifier, but it doesn't hurt either.

IMO the only reason to use the GM would be is if you like to visit the dealer's parts department and/or pay a little more.

Anyone know if that part number oil is synthetic? I bet it is. I think it is used in open and LS just like the Mobil 1. Hell, it wouldn't surprise me if it IS Mobil 1.

 

Just changed mine, a couple of notes about what I found. Since the store didn't have enough of one brand of fluid, I used Amsoil in the front and Mobil 1 in the rear.

The front fluid was kind of green but pretty clean looking. When I took the fill plug out extra fluid poured out. Not a lot but it was definitely overfilled. Maybe a couple of ounces, less than a cup. And this was with the front wheels up on ramps so the plug side was tilted up a little. When I refilled it I could only get 1 quart in, the specs called for 2.7 pints. Based on the shape of the housing I doubt the tilt prevented any of the old fluid from draining.

I changed the rear with the truck on level ground. The fluid was dark brown, definitely not the same as the front. Maybe the rear differential is harder on the fluid, I rarely use 4WD. I did use close to 3 pints refilling the rear.

Neither the front nor the rear magnetic plugs had much on them, just a small amount of very fine metal filings.

I've heard that synthetics may improve my mileage a little, but maybe not enough to notice. We'll see.

DC

 

At what mileage intervals is it recommended for differential fluid change? I know my manual does not show the differentials on the mileage maintenance schedule, although does give the fluid type? Unlike the transfer case which is listed in the mileage schedule at 45,000.

 

Just did the diff oil change in mine...30,000 miles. Fluid in the rear was black, the magnet had 1/4" of crud built up on it. Fluid in the front I noted some drained out the fill hole, maybe a cup or so. The front fluid looked clean, almost as clean as new. I've not had it in 4x4 mode for awhile, typically only winter or if I have a trailer stuck in the mud do I use it.

Bought 3 quarts of Mobile 1 Synthetic 75-90, have 1/3 qt left thereabouts...some overfill poured out but not much.

 

Just did the diff oil change in mine...30,000 miles. Fluid in the rear was black, the magnet had 1/4" of crud built up on it. Fluid in the front I noted some drained out the fill hole, maybe a cup or so. The front fluid looked clean, almost as clean as new. I've not had it in 4x4 mode for awhile, typically only winter or if I have a trailer stuck in the mud do I use it.

Bought 3 quarts of Mobile 1 Synthetic 75-90, have 1/3 qt left thereabouts...some overfill poured out but not much.

I did a fluid change back about a month ago and I used Lucas full synthetic 75/90w like yours mine was black and the front was still clean so I didn't change it. My mileage was only about 15,000 and it was really black. I will check it again next summer to see how it looks.

 

I'm sure I'll be tempted to see how dark the fluid in the rear diff is come spring time...

Since changing out the fluid though, is it overkill to check the level after a few miles?

 

I would argue that it is good practice to check any fluids you change after a few miles.

 

Similar experience here at 20K miles. Front diff fluid looked good, came out of the fill hole (level ground). Rear fluid was dark brown and some sludge, did not come out the fill hole, seemed slightly underfilled.

Seems to be that if one wants to, skip the front and just do the rear would be just fine. What are people finding with the transfer case fluid? Is it worth doing?

Did the fuel filters too, they did not look bad, no water in the filter box and no loose mung, just stained dark. The fuel filter system and access for changing diff and TC fluid is wonderful on these trucks.

 

Easy job! Drop the spare tire. Everything opens up. About 3 beers to do. Hah. Mine was 50000 and some darkening. Changed anyway with mobil 1 without the additive. Back was so good i thought screw the front. Ill wait another 25000 before i think about doing the front. Hope it helps!

 

I have a 2019 ZR2 with the full lockers. It has 26k on it. after reading about how the factory fluid looked with such few miles and metal on the magnet, i am wondering if I should change the rear differential oil. With the locker, can I use synthetic in it or not? and I'm assuming it should be the 75w90 or whatever normal rear end oil is. Also, i think i'd read that later models didnt have a drain plug any longer. Does a '19 still have the drain plug? I havent looked yet.

 

I don't know about the drain but you can use any 75W 90 on the locker. It doesn't have clutches like the G80 auto locker so no worries about friction modifier either.

 

I put grease on the outside inside the square plugs to help prevent rust and dirt grime from accumulating in them.

 

I wish they had it in the maintenance schedule. Been following that and just stumbled upon this thread with 82k on a 2019 Canton 3.6l. guess I'll be changing it ASAP.

 

'21 Colorado Lt, Duramax Diff's are new to me, front looks easy, but my aft diff doesn't have a drain plug. I'm almost 70k into this truck, and didn't know I should have done it a while ago. Recommendations for changing adt diff without drain plug?

 

Loosen the cover bolts and let it drain into a pan, then remove the cover, clean the gasket and mating surfaces, and then refill.