Poll: When Do You Change Your Rear Diff Oil?

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GM does not appear to have a maintenance frequency for differential oil. The manual simply says to "check fluid level". A lot of folks do an initial break-in change, others wait until 50k miles (lots of towing, etc.), some go ~100k, and some could care less. I'm curious what folks here do?

[MS3DALE]

I change it for the first time at 3k,then about every 15-20k after that,I do the front axle and transfer case fluids as well

[Stevens03]

I actually changed mine at 1000 miles, and then 50,000

[killterrorists]

I changed the rear fluid on my current truck at 170k. It smelled like grapes and had a good bit of metal on the magnet so i'm guessing that my change was the first.

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I should have said "when do you do your first change", since anyone that does it in less than 5000 will probably do it more frequently from that point forward. The GM grape juice is crazy expensive (quoted $35/qt @ dealer), but I have read where folks use Mobil 1, Redline, Amsoil, etc. instead. I have also read that Mobil 1 75W90 does not meet the GM spec (on Mobil's web site). They don't say it won't work, only that it doesn't meet the GM spec. I read an email response from AMC on one of the RV sites a while back, specifically answering this question. They basically said that it helps to change out the original break-in fluid (not required, but probably helpful), especially if you tow heavy loads during that first 500 miles. Nothing to do with metal shavings, but simply that the temps get higher during break-in and that it could affect the oil. They then say that the 2nd fill (post break-in) could be considered "fill for life". I suspect that GM chose to state "don't tow in the first 500 miles" in the manual, and considers the original fluid as "fill for life" if you don't. Don't really know... but the manual makes no mention of changing the fluid that I can find (?).

[brainpause]

Bought my truck with 9K on it, so I don't know if my recent 50K change is the first.

 

I guess I'll be the guinea pig. I put Royal Purple 75W-90 in both diffs. I'm not gonna lose sleep.

 

After all the various debates, I have decided that I will simply change all drivetrain fluids every 50K miles.

 

Larry

[tanked_darren]

I do it when I do the transmission filter, every 50,000miles or 80,000kms where im from. I get the oil for free and figure, hey why not.

[kdixer]

I changed both diffs and transfer case on my 09 for the 1st time @ 28,000 miles. The front diff fluid looked like nothing I had seen before. It was a dark silvery grey color. Almost like the aluminum housing had some sort of reaction and discolored the fluid. The transfer case fluid looked decent and the rear diff looked normal. All 3 had significant metal powder stuck to the magnets which is most likely just from break in. The transfer case and front diff had magnetic drain plugs. The rear diff has magnetic strips on the inside of the cover positioned where the ring gear will "rooster tail" the oil towards it. My rear diff had a rubber gasket installed from the factory so it was just a matter of wiping off the oil and reinstalling the cover.

 

I used Mobil 1 75 90 in the diffs and Dexron VI in the transfer case. I mainly decided to change them due to the past 2 winters being rather harsh and requiring the use of 4wd so much.

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I used Mobil 1 75 90 in the diffs and Dexron VI in the transfer case. I mainly decided to change them due to the past 2 winters being rather harsh and requiring the use of 4wd so much.

 

Notice any issues with the G80 using Mobil 1?

[kdixer]

I used Mobil 1 75 90 in the diffs and Dexron VI in the transfer case. I mainly decided to change them due to the past 2 winters being rather harsh and requiring the use of 4wd so much.

 

Notice any issues with the G80 using Mobil 1?

 

 

 

No issues yet. But short of grenading something I really do not know how people can tell if one fluid is better than the other. The g80 still locks up as it should. I accidentally tested it on a wet paved hill.

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The g80 still locks up as it should. I accidentally tested it on a wet paved hill.

 

That's all that matters. I've read reports that it stopped locking up, or didn't do it as well. If it locks "correctly" now, it should forever. The question stems from the amount of slip additive, since both meet the GL5 spec. The GM stuff has a specific amount in it already, but the Mobil 1 is different. Well, that's what I've summarized from reading. I didn't stay at a Holiday Inn Express last night though and have no factual info, so take it as an internet reading guess. The part about Mobil 1 not meeting the GM spec, however, was right on the Mobil web site (somewhere in the Q/A section).

[kdixer]

I mainly meant that some people get on here and make claims to how good their truck performs with Royal Purple or Amsoil. I have no idea how there is enough of a difference for them to literally tell by seat of the pants. It just seems like they would need long term testing and comparison to make those claims unless something grenades on them.

 

Here is an interesting read on gm's specs:

http://www.dieselplace.com/forum/showthrea...8610&page=3

[ChevyTech77]

I couldn't vote but once at the first oil change and then once a year, for a locking rear diff.

 

Otherwise, once ever 50k should suffice for an open diff. I still do my open once a year with the front, transfer case and trans but I'm kind of anal about my stuff.

[crepitus]

Quick question. I actually bought the oil last year to do this and still haven't got around to it because no place stocks a gasket. I saw in a previous post about a reusable rubber gasket. Do they all have this?

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I couldn't vote but once at the first oil change and then once a year, for a locking rear diff.

 

Otherwise, once ever 50k should suffice for an open diff. I still do my open once a year with the front, transfer case and trans but I'm kind of anal about my stuff.

 

What oil do you use?