Doggone Gear Oil Question

[xaugievike]

 

OK - after a season of heavy towing I want to change out my differential oil in preparation for some upcoming trips.....now I've done this job before on trucks from another brand, but my searches on the topic for my truck have me truly stumped as every result produces an equally opposite opinion in every other thread....

 

Mobil 1 75-90 sounds like it's OK for me to use. My searches seem to indicate I dont need to worry about the friction modifier.

 

So I go to my local Autozone to pick up the stuff (hate going there by the way) and on the shelf they have 75-90, right next to 75-90 LS (????)

 

of course they didnt have enough of either to complete the job anyway, so I'll try again tomorrow...but what's the difference between those 2 oils?

 

and since I have your attention....is my understanding of the need for a friction modifier accurate or not?

 

and is there a need to put some sort of sealant on the differential drain plug threads?

 

Thanks guys....sorry for the silly post....my frustration is just rising b/c I'm managing to stretch this 20 minute job out into a weekend long affair....

[brims]

Every time I've bought Mobil 1 75W-90 it has been LS, that's all I've seen on their website. My G80 still works fine with the LS fluid. Pissed me off when I realized that it was LS, but it still works so I'm fine with it.

[RyanbabZ71]

The modifier is only needed for the old body style (99 and earlier) trucks. The 99+ NBS trucks do not require it.

[xaugievike]

The modifier is only needed for the old body style (99 and earlier) trucks. The 99+ NBS trucks do not require it.

 

so this Mobil 1 "LS" is ok to use?

[RaddHazzard]

I believe mobil now only offers 75w90 in the LS version, the non LS gear oil is being fazed out. I think i read this on the mobil website. You do not need to add friction modifier unless you experience chatter, which you should not. Im sure putting thread tape on your drain plug wouldnt hurt, although if there is no sealant on it currently and it doesnt leak, its probably not needed. I do use it on my TC bolts though.

To clarify, I would buy the correct amount of mobil gear oil, be it a mixture of LS and non-LS, and you should be fine.

[Ryan00TJ]

I used the M1 75W-90 LS Syn in mine. Both front and rear. No problems. I've used the M1 for years in various apps with great results. You don't need to add anything with the Eaton Auto locker. It's gear to gear engagement and does not require friction modifier. I did have to use it with the M1 in my Camaro SS but that was due to the Zexel Torsen limited slip in the rear axle that required the friction modifier.

[thearborbarber]

I have bottles of each in the garage and they have the same text on them except the LS says LS

[Irv]

I used the M1 75W-90 LS Syn in mine. Both front and rear. No problems. I've used the M1 for years in various apps with great results. You don't need to add anything with the Eaton Auto locker. It's gear to gear engagement and does not require friction modifier. I did have to use it with the M1 in my Camaro SS but that was due to the Zexel Torsen limited slip in the rear axle that required the friction modifier.

 

 

Sorry to bring up an older post but this is what I found in the search feature.

 

Just curious if it is ok to use the Mobil-1 syn 75-90 LS in both the front and rear diffs on my truck?

My truck is an 09 Sierra slt 4x4 with the 5.3 engine(doubt that matters?) and I currently have about 27,000km's on it.

 

Also curious on how much fluid (approx) each diff takes?

Thanks.........Irv

 

Edit: meant to add, front diff calls for 80-90 and rear 75-90 synthetic, any worries running the 75-90 syn in the front diff as well?

[Superperv23]

I used the M1 75W-90 LS Syn in mine. Both front and rear. No problems. I've used the M1 for years in various apps with great results. You don't need to add anything with the Eaton Auto locker. It's gear to gear engagement and does not require friction modifier. I did have to use it with the M1 in my Camaro SS but that was due to the Zexel Torsen limited slip in the rear axle that required the friction modifier.

 

 

Sorry to bring up an older post but this is what I found in the search feature.

 

Just curious if it is ok to use the Mobil-1 syn 75-90 LS in both the front and rear diffs on my truck?

My truck is an 09 Sierra slt 4x4 with the 5.3 engine(doubt that matters?) and I currently have about 27,000km's on it.

 

Also curious on how much fluid (approx) each diff takes?

Thanks.........Irv

 

 

Yes you can run 75-90 in both and front is 3 pints and back is 4.3 so just get 4 quarts of oil and fill them to fluid is level with the bottom of the fill plug

[Irv]

I used the M1 75W-90 LS Syn in mine. Both front and rear. No problems. I've used the M1 for years in various apps with great results. You don't need to add anything with the Eaton Auto locker. It's gear to gear engagement and does not require friction modifier. I did have to use it with the M1 in my Camaro SS but that was due to the Zexel Torsen limited slip in the rear axle that required the friction modifier.

 

 

Sorry to bring up an older post but this is what I found in the search feature.

 

Just curious if it is ok to use the Mobil-1 syn 75-90 LS in both the front and rear diffs on my truck?

My truck is an 09 Sierra slt 4x4 with the 5.3 engine(doubt that matters?) and I currently have about 27,000km's on it.

 

Also curious on how much fluid (approx) each diff takes?

Thanks.........Irv

 

 

Yes you can run 75-90 in both and front is 3 pints and back is 4.3 so just get 4 quarts of oil and fill them to fluid is level with the bottom of the fill plug

 

 

 

Thanks superperv, thought so myself but thought I had better ask.