Best Rear Differential Fluid for 1987 Silverado

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PenguinBuddy

Joined
May 10, 2024
Messages
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I have a 1987 Chevrolet Silverado R10 (700 R4, 10-Bolt Rear) that has a leaky rear differential. I have all that I need to replace the gasket, but I am going to be putting new fluid in, and wanted to see what would be best. Background information: the rear end was rebuilt back on 10/18/2016, and it has not needed to be serviced until now. The owner's manual states that SAE-80W-90 GL-5 is the reccomended fluid and lubricant. To my knowledge, SAE-80W-90 GL-5 is what was used after the rebuild, and is still what is in the rear differential. While I do think that the rear end was rebuilt well, it has always (since the rebuild) had a slight howl at speed.

My question is two-fold. Is there a "best" lubricant that would be a higher quility for the long-term? I have seen discussions on this forum regarding Redline products, and discussing their superiority. I have also seen posts that caution against using any lubricants with a friction modifier or posi additives, per a GM service bulitin. I defintely don't want to make a mistake and get something that includes those, which also pushes me toward something like Redline. The other aspect to my question is surrounding the noise, and if an increase in weight would result in the noise being cut down at all, which I have also read on a few forums.

Thanks in advance for any advice that you have!
 
jhellwig said:
Don't overthink it. If it is working just put whatever fluid in it you can get. It isn't going to die anytime soon.
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Easy enough! I have MasterPro SAE-80W-90 GL-5 on the shelf already. Just wanted to be sure that I was not missing anything.
 
SubieRubyRoo said:
I’d probably think it just a little harder than that…😱

Good gear oil is not that expensive.
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I’m more than happy to spend money on something else. Just not sure how best to choose. Wondering if I should look to quiet the noise too…
 
PenguinBuddy said:
I’m more than happy to spend money on something else. Just not sure how best to choose. Wondering if I should look to quiet the noise too…
Click to expand...
The noise is likely inherent to your specific bearings, or caused by slightly-off pinion depth. It’s likely not detrimental, just something to bug you… not likely any lube will quiet a whine; certainly not after 8 years.

Just find your fave on the J2360 list and change it once every 5 years whether it needs it or not, unless it’s been submerged during that time. Then, change it as soon as you possibly can. 👍🏻
 
SubieRubyRoo said:
The noise is likely inherent to your specific bearings, or caused by slightly-off pinion depth. It’s likely not detrimental, just something to bug you… not likely any lube will quiet a whine; certainly not after 8 years.

Just find your fave on the J2360 list and change it once every 5 years whether it needs it or not, unless it’s been submerged during that time. Then, change it as soon as you possibly can. 👍🏻
Click to expand...
That makes the most sense to me! I’m going to be changing it out this week, and I’ll keep up with it really closely after that. Truck was out of commission for a little while over the past few years, hence the delay in service.
 
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