Jaxon2580

Hi everyone,

I have a 2003 Silverado 2wd with 114,000 and I wanted to change my diff fluid but I needed to know what kind I had, it's a 10 bolt diff and my only code I haveis GU6 no G80 code, does that mean it's an open diff??

Also, if it is open, just about every fluid now a days has limited slip friction modifier added, is it okay to use it in an open diff? Like royal purple for instance? Thanks!

silverado.408

iTrader: (1)

If its an open diff it doesn't matter as there are no clutches as in a limited slip that has clutches or gears. Pull the cover if you can . If you have just spider gears then its open. If you have spider gears with springs and other goodies its a LSD. If its like mine its just an open diff. I threw Mobil one in and left it alone. No additives

oakley6575

iTrader: (5)

I found there wasnt enough additive in the limited slip gear oil. So I would add a bottle to whatever fluid you use if you find out you have a posi.

Jaxon2580

The thing is everything good these days has limited slip additive and im 90% sure it's just a open diff since there isn't any code in the glove box for g80, just GU6(3.42 ratio). I just wanted to make sure i just wanted to make sure I could use something with the additives in case mine is an open diff

Jaxon2580

So I'm fine using any fluid in case it's an open diff? Such as royal purple 75w90

silverado.408

iTrader: (1)

My oil in my diff is burned from welding stuff and runs fine.(open diff). If your changing fluid just go royal purple and be done if its a LSD. If its open the basic stuff works fine. I run royal purple in my wife's Z28 Lsd no additives runs great 3 years now.

Jaxon2580

Sweet great to know! Im probably going to run royal purple either way though

Slowest_1500

I did mine just this past week, I used Mobil 1 75-90, 3 bottles, and went ahead and changed the cover and gasket could of used maybe a little more but I work at Valvoline so I just grabbed a little from the shop, doesn't really matter if it has LS additives. Just put a synthetic in the diff, and don't do drain and fill take the cover off and clean the magnet or else all the metal shavings and gunk will contaminate the new oil. remember check the bolts after 100 miles and make sure they're snug.


Also just a personal thing I wouldn't use royal purple man, don't trust the stuff, heard some pretty bad stories from friends and have seen it destroy a diff before, maybe it wasn't the oil maybe it was.. all I use is Mobil 1 in all my cars and I work for Valvoline for crying out loud! But that's just me

good luck!

Jaxon2580

Oh yea I was definitely going to take the cover off to clean the magnet, I'm going on a hunch the original owner never even touched it so Im going to replace the gasket and everything, buti didn't know that about royal purple gear oil.. how about amsoil? Or just go with something cheap?

Slowest_1500

AMSoil is really good, hard to find down here in Miami or else that's what I would go with. I wouldn't cheap it out man unless you're going to change gears or go posi sometime real soon but if that's the case just hold off, I've seen some pretty nasty sh*t working for this company, most of the time due to prolonged maintenance intervals and cheap products..I've seen and smelled things come out of diffs that'll make most throw up.