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GM diff fluid. #5380694 03/19/20 07:47 PM
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WillB Offline OP
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I traded my Jeep for a 17 silverado 1500. I have Amsoil 75w90 that I can use in my front diff, but wonder if 75W140 will be ok in my rear G80? I bought this for my Jeep, never changed it.


Thanks,

Will

2017 Chevy Silverado 1500 4x4 QC LT True North Edition.
2011 GMC 1500 CC 4WD 4.8 - Traded.
04 GMC 1500CC Z71 350,000km 217,000 miles - Retired.
Re: GM diff fluid. [Re: WillB] #5380701 03/19/20 08:01 PM
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BlakeB Offline
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Should be fine. I think those call for 75w85, but 75w140 shouldn’t hurt anything. [Linked Image]

Last edited by BlakeB; 03/19/20 08:02 PM.
Re: GM diff fluid. [Re: WillB] #5380702 03/19/20 08:02 PM
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zeng Offline
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It's fine , with a grade or two thicker gear oil than OEM recommended in any gear train system .

Re: GM diff fluid. [Re: WillB] #5380703 03/19/20 08:03 PM
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4WD Offline
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You don’t have enough Amsoil for the rear ? That’s going to do the high RPM work.
I have owned GM 4WD’s for many, many years (have 2017 & 2018 now) and never went above 75w90 … mostly Mobil 1 or Delvac 1 75w90

Re: GM diff fluid. [Re: WillB] #5380705 03/19/20 08:05 PM
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BlakeB Offline
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Mix the 75w90 and the 75w140 in equal parts and use the mix for both the front and rear. The mix be close to a 75w110.

Re: GM diff fluid. [Re: WillB] #5380715 03/19/20 08:19 PM
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WillB Offline OP
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Thanks. I will order more 75W90, will use the 140 in mower gearbox.

Does the G80 require any additives?


Thanks,

Will

2017 Chevy Silverado 1500 4x4 QC LT True North Edition.
2011 GMC 1500 CC 4WD 4.8 - Traded.
04 GMC 1500CC Z71 350,000km 217,000 miles - Retired.
Re: GM diff fluid. [Re: 4WD] #5380719 03/19/20 08:22 PM
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gman2304 Offline
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Originally Posted by 4WD
You don’t have enough Amsoil for the rear ? That’s going to do the high RPM work.
I have owned GM 4WD’s for many, many years (have 2017 & 2018 now) and never went above 75w90 … mostly Mobil 1 or Delvac 1 75w90

^^ I use the Delvac 1 75w90 in my G80 locker. It doesn’t contain LS additives.

Re: GM diff fluid. [Re: WillB] #5380739 03/19/20 08:43 PM
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BlakeB Offline
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Originally Posted by WillB
Thanks. I will order more 75W90, will use the 140 in mower gearbox.

Does the G80 require any additives?

The GM grape scented stuff does have some LS modifier. But there are plenty of people using Delvac 75w90 that doesn’t have any modifiers in it.
On the flip side there are a lot of people using Amsoil severe gear on their G80’s, the Amsoil has LS additives in it.

I talked to a blender about it when I was researching what to use in my 3500HD. The spec for the Grape scented 75w90 does call for LS additives in a very small dosage.

Re: GM diff fluid. [Re: WillB] #5380777 03/19/20 09:34 PM
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Snagglefoot Offline
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If we were talking about Texas, I’d vote for 75W140, but the OP is from Innisfil, Ontario. 75w90 is fine. I have 200,000 miles on my diiff using Synthetic 75w90.


If you want the job done right......do it yourself.
Re: GM diff fluid. [Re: 4WD] #5381003 03/20/20 08:05 AM
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Railrust Online Content
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Originally Posted by 4WD
You don’t have enough Amsoil for the rear ? That’s going to do the high RPM work.
I have owned GM 4WD’s for many, many years (have 2017 & 2018 now) and never went above 75w90 … mostly Mobil 1 or Delvac 1 75w90


Same, and doesn’t the newer GM’s suggest 75w85 for the rear now? I simply put Mobil 1 75w90 in and call it a day. No issues.

I’m a bit anal with my maintenance...I change it once a year whether it needs it or not. Drive about 26,000 a year anyway.


2018 Chevy Silverado 5.3
2007 Lexus LS460 (deceased)
2008 Honda CRV
(Whatever synthetic oil is on sale or rebate)
Re: GM diff fluid. [Re: Snagglefoot] #5381005 03/20/20 08:06 AM
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Originally Posted by Snagglefoot
If we were talking about Texas, I’d vote for 75W140, but the OP is from Innisfil, Ontario. 75w90 is fine. I have 200,000 miles on my diiff using Synthetic 75w90.


Should be more than fine, his truck calls for 75w85.


2018 Chevy Silverado 5.3
2007 Lexus LS460 (deceased)
2008 Honda CRV
(Whatever synthetic oil is on sale or rebate)
Re: GM diff fluid. [Re: WillB] #5381066 03/20/20 09:06 AM
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Snagglefoot Offline
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What’s mind boggling is that the owners manual for a 2017 Silverado 1500 does not list changing the differential fluid as a maintenance item. crzy

Last edited by Snagglefoot; 03/20/20 09:08 AM.

If you want the job done right......do it yourself.
Re: GM diff fluid. [Re: WillB] #5381085 03/20/20 09:32 AM
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SilentForever05 Offline
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Originally Posted by BlakeB
Should be fine. I think those call for 75w85, but 75w140 shouldn’t hurt anything. [Linked Image]

I live in a tropical climate with high temp all year round. Would I benefit from switching to let's say 85w-140 if my manual calls for 85w-90? Thanks!

Re: GM diff fluid. [Re: WillB] #5381221 03/20/20 12:36 PM
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LDM Offline
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I just did my front/rear differentials on my 18 last weekend. The front calls for 75w90 and the rear 75w85. I used Vavoline Full Synthetic 75w90 on both differentials. 75w85 is difficult to find and expensive and is barely any different from 75w90. I think they do the 75w85 for CAFE on these trucks. When I had my 15 I did the same thing and had no issues there either.

You could probably run 75w140 as well, I really don't think it will make much of a difference either. Probably doesn't need it unless you are constantly towing heavy loads or racing the truck.


2018 GMC Sierra 1500 SLT 6.2 Max Tow
1994 Chevy Camaro Z28 5.7
1989 Chevy Camaro IROCZ28 5.7
Re: GM diff fluid. [Re: WillB] #5381453 03/20/20 05:12 PM
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BlakeB Offline
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[Linked Image]
I borrowed this from here.

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