2013 Tahoe diff oil recommendations?

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Aug 5, 2010
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I have a 2013 Tahoe 5.3L 4x4 160,000 miles and unknown drain and refill history. I would like to change the front and rear diff fluid along with the transfer case.
In my owners manual the transfer case calls for Dexron VI fluid, no big deal and widely available.
The front diff calls for 80w90 but some online reading says that 75W90 can be used.
The rear diff calls for 75W90 synthetic. I assume at this point I can use the same fluid for the front and rear diff. I can’t find any information if friction modifier should be added or not for front and rear differential. Some say no, some say add it in and it won’t hurt.
Also my front pinion seal has a little bit of weeping. It’s not anywhere near dripping. Is there such a thing as high mileage gear oil to condition the seal?
What’s your ideas on the correct fluid to ise in my situation?
 
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I have never seen high mileage gear oil, and I don't know if 2013 seals are a lot different , but my 65 mustang that is a show/summer car only had a differential pinion seal leak bad enough that about every 2000 miles I would add a little oil to it. As it took over a year to put those miles on, it was no big deal. I added a little of some brand of engine oil stop leak to it, and within less than a year, the leak stopped, and I haven't had to add any for several years now.
 
I alway buy the gear oil with the LS additive already in it although I don't particularly need it for my apps.

I like and have had good success with synthetic Mobil1 75W90 w/LS.
I also keep around, a gallon jug of conventional PEAK 80W90 w/LS that I bought from PepBoys some time ago for about $14/gal.
IDK how much it'd co$t today.

IMO, the difference between conventional 80W90 or synthetic 75W90 doesn't matter as much in gear oils. However, the LS additive is important where applicable. Am I wrong?
 
I alway buy the gear oil with the LS additive already in it although I don't particularly need it for my apps.

I like and have had good success with synthetic Mobil1 75W90 w/LS.
I also keep around, a gallon jug of conventional PEAK 80W90 w/LS that I bought from PepBoys some time ago for about $14/gal.
IDK how much it'd co$t today.

IMO, the difference between conventional 80W90 or synthetic 75W90 doesn't matter as much in gear oils. However, the LS additive is important where applicable. Am I wrong?
At least on my 2005 (but I don't believe this ever changed on the newer ones) it's a mechanical locker in the rear end and isn't supposed to take LS additive. Front is open diff so also no LS additive.
My 84 Oldsmobile takes the LS additive because it's a clutch style posi.
 
Right, I get it. However, the LS additive won't hurt anything and it covers all bases unless you need more/stronger dose. And I like keeping it on hand.

The Firebird in my signature doesn't require an LS additive in the rear differential as it is not limited slip nor post. But I use gear oils with the LS additive anyway. Same for my wife's previous Lexus RX AWD. It didn't require the LS additive for the rear diff nor tc but I used it there too.

It's not as though using the LS additive hurts a non limited slip diff. As you stated, it's just not needed.(y)
 
I went with Amsoil's 75w90 at the time because I had the preferred customer discount thing. If I were to do it again, I'd probably just get something off the shelf at Walmart.
 
The cheapest 75w-90 without a LS additive I found was through Autozone. Chevron Delo and it’s working great in my Silverado front and rear diffs.
 
After seeing some of the replies I'm wondering if there is any benefit to the LS additive in a g80 locker rear end that doesn't call for it?
Mine occasionally gets stuck locked up after spinning the tires, previously it seemed to be fixed by changing the fluid. Late last winter it happened a couple of times again and the fluid only had maybe 20k-30k miles at most...it hasn't happened since then and I forgot all about it but the time of year for spinning tires is coming up again. The fluid will be getting changed along with a leaking axle seal over the holidays.

I want to use the best fluid I can in this as the rear is a weak point on these and it's at 215k miles. I will probably hit 400k so a rear end rebuild is likely at some point.
 
The G80 requires a friction modifier to keep the clutch packs happy. I believe most of the major brands have included it, the fine print on the bottle may say. There is a friction modifier additive available but you have to make sure to use it only when necessary because too much is as bad as not enough.
Thicker is not always better, the hard work has been done, the people that design, build and warranty the diffs say 75W90. Thats good enough for me.
We used a well known ring and pinion shop when I was still working, they do hundreds of diffs a year, this was their advice
 
The G80 requires a friction modifier to keep the clutch packs happy. I believe most of the major brands have included it, the fine print on the bottle may say. There is a friction modifier additive available but you have to make sure to use it only when necessary because too much is as bad as not enough.
Thicker is not always better, the hard work has been done, the people that design, build and warranty the diffs say 75W90. Thats good enough for me.
We used a well known ring and pinion shop when I was still working, they do hundreds of diffs a year, this was their advice
The g80 in the GMT 800 trucks is an Eaton locker, no clutch packs, it calls for synthetic 75w90 no posi additive recommended. I did some through checking on this when I changed it a couple years ago, since there seems to be a lot of confusion on the matter and even the shop I had working on the truck (where I used to work) thought it was supposed to have the additive. I'm still curious whether there is any benefit to the additive when it's not called for like in this application. The truck spends most of its time right around the max gvwr, sometimes going off road and through deep snow as required for land surveying.
 
Reference the attached address from Eatons website, note the mention of " clutch packs"
Look in the search and you will find previous threads on additive. GM even had a TSB on it back in the early 2000's (I dont have access to it)
I have had a number of trucks personally and in the work fleet with this diff, we always ran 75W90 in them with friction modifier for the G80. If you know whats supposed to be in them why do you keep asking ?
 
Reference the attached address from Eatons website, note the mention of " clutch packs"
Look in the search and you will find previous threads on additive. GM even had a TSB on it back in the early 2000's (I dont have access to it)
I have had a number of trucks personally and in the work fleet with this diff, we always ran 75W90 in them with friction modifier for the G80. If you know whats supposed to be in them why do you keep as
I was sure I had read the previous threads on this and it had been confirmed that they didn't call any additive, but I'll recheck those threads later on. I could have remembered wrong.
 
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