Diff oil recommendation: '17 Silverado 1500 towing 7000# travel trailer

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I own a 2017 Silverado 1500 Crew Cab 2wd 5.3 w/ 3.42 and towing package (not Max Trailering). Currently it has about 18k miles on the odometer and I'm the original owner. I figure around 30-33% of the miles on the truck were driven while towing a 6500-7000# travel trailer (dry weight + gear in trailer). I use a proper weight distributing hitch and I am not one of those maniacs you see driving 90mph while pulling an overloaded trailer. We take between 5 and 7 trips each year (500 miles round trip) pulling the travel trailer. The travel trailer is almost paid off and we plan on driving the truck for at least 10 years (or more), so I estimate the truck will see at a minimum 25% of its miles driven per year pulling a trailer over the span of its life. Even if we sell the travel trailer and buy another one in the future, its replacement will be approx the same weight. I have been contemplating changing out the rear diff fluid because I feel the truck falls under the "severe service" category. The truck started pulling the trailer right after 1k was on the odometer. GM recommends their 75w85 p/n 19300457 non-sense for the 9.5" diff. Questions, * Is changing out the diff fluid around 18k-20k miles still too early, or is that a good plan for preventative maintenance since the truck pulls a heavy trailer 5-7 times a year? * Do I need to stay with the 75w85 to stay in my warranty? I have the GMPP 7 year plan. * If I used 75w90 diff oil, would the dealer even know it was changed if there was ever a warranty claim regarding the diff? * Is the forum's consensus still the same, regarding that 75w90 is recommended for GM applications requiring 75w85? * Is there any benefits with using the AC Delco 75w85 over 75w90? * For those who have serviced a '14-'19 Chevy 1500 9.5" axle, is the gasket reusable or should I replace it with a new one? If it's advisable to replace the gasket, use a Fel-Pro? * If I went with a 75w90, it will probably be either Mobil 1 or Valvoline synthetic. Any other recommendations that can be found in the $9-$13/qt range ? Your opinions, suggestions and experiences are appreciated! thanks
 
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Do you have the G80 locker? If so, you want to avoid the stuff with the limited slip additive. This is according to Eaton when I contacted them about what fluid to use. They told me that syn isn't required for the G80, but I'm pretty sure GM requires it, but you don't want any LS additive. When I do mine, I'm planning on Delvac 1 75W-90 since it's a great gear lube with no LS additive.
 
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I prefer Amsoil SVG, it has served me well in all applications. I like 75W-110 in the rear, 75W-90 in the front. Changing the fluid is not going to void your warranty. They don't require you use GM fluid and they aren't going to test it to see if it is a different viscosity. Not that they could easily tell the difference between 85, 90 or 110 weight gear oil once it is used. As for the gasket, I've never serviced anything newer than a 2013 Suburban and the reusable gasket made the job super easy. Came off cleanly and went on leak free after cleaning it up. I love it. I would never replace it with a Fel-Pro. I don't think it is ever too early to change out the factory fill. That is probably the most important change in oil, getting out the metal from break in. After that I'd easily go 50k miles with synthetic without a worry.
 
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Yes, it's time to change the rear diff fluid. 75W-90 Mobil-1 or Valvoline Syn fluid will serve you well. That was short and sweet...
 
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Most axle wear occurs from 0 to 15K miles or so and despite longer and longer runs the wear metals will continue to drop so you are spot on to change it at 18K. I would run Amsoil 75W-110 in it because 75W-110 is the upper viscosity that 75W-90 used to be before the SAE J306 tables were updated. I definitely would with the towing that you are doing.
 

Islandvic

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Thank you for all the responses.... I've used Amsoil in the past, in other vehicles and had to pay for the Preferred Customer deal. Is that still the only way to buy Amsoil and not pay full retail? Or are there other vendors now to buy it from for below their listed retail price? @K20FA5, yes it has the G80 locker, 9.5" with 3.42 gears. So I wasn't going to add the LS additive, but I now have a question...... M1 75w90 LS is marketed for use with LSD's. So is that the same as the LS additive that is available separately making the M1 not a viable option ?? @Wishihadatruck, I wasn't sure if my 2017 had a reusable gasket, but your 2013 'Burban had one? Did you use something like Permatex High Tack Gasket Sealant, or just put the reusable gasket on dry ?
 
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Originally Posted by Islandvic
I've used Amsoil in the past, in other vehicles and had to pay for the Preferred Customer deal. Is that still the only way to buy Amsoil and not pay full retail? Or are there other vendors now to buy it from for below their listed retail price?
Ping Pablo on here; he will give you a good price on it.
 

Islandvic

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@2015_PSD, are you talking about the Pablo ? I haven't been active for a while on the forum, but I remember Pablo from way back in the day! I just realized I joined back in 2005. Ha
 

4WD

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Long term owner of many GM 4WD's with G80's here … save money and get Delvac 1 from Summit Racing (racing site selling HD gear oil for the Porsche track guys) … It carries pedigree from several OTR truck builders … Might have to spend $100 for free shipping … (gallon and/or quarts sold) I used M1 for 20 years but went to Delvac 1 about 4 years back … in both my G80's now
 
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I'm towing about 7200 with the avalanche, now my diff was rebuilt with a trutrack in place of the stock unit. The gear shop installed and advised me to use 85-140 for towing, so thats what i have in there now, i have changed it once. I may again in the spring.
 
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Originally Posted by Islandvic
@2015_PSD, are you talking about the Pablo ? I haven't been active for a while on the forum, but I remember Pablo from way back in the day! I just realized I joined back in 2005. Ha
Yes - "the" Pablo. grin2
 
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It doesn't make that much difference with gear oil. In drag cars going 150 mph, a light breeze headwind had more effect on mph and elapsed time than going from a 75w-90 to 75w-140.
 
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85/140 hasn't changed my mpg that's noticeable My avg mpg is still pretty much what it's always been
 
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Originally Posted by K20FA5
Do you have the G80 locker? If so, you want to avoid the stuff with the limited slip additive. This is according to Eaton when I contacted them about what fluid to use. They told me that syn isn't required for the G80, but I'm pretty sure GM requires it, but you don't want any LS additive. When I do mine, I'm planning on Delvac 1 75W-90 since it's a great gear lube with no LS additive.
I used DELO 75W90 and I am satisfied I did the truck seems to run better and quieter. I changed my rear around 50K miles and there was some metal shavings but not bad at all.
 
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changing ALL my drivetrain lubes to Redline netted me 3mpgs on my 2011 fronty SV 75-90 in rear not OE 75-140 semi syn, theres 75-110 as well
 
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