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Discussion Starter #1
Valvoline, Lucas, Mobil 1 and Royal Purple are available to me locally. Any one better than other? Royal Purple is almost 2X’s the price of the others.
 

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Stay away from Lucas and RP. I believe the PQIA had run tests on Lucas products and found them inferior or not even to spec. RP is just way over priced. You wont see any benefit for spending that extra money. Similar to Amsoil.

Find one that is GL5, J2360 rated. Nothing wrong with Valvoline or Mobil. Pick the cheapest.
 

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I have been using the Mobil1 the last few changes, the 75W90 that is specified for limited slip diffs, it has been working very well for me.
 

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I run RP only because it was readily available to me at the time and it was full synthetic and came in the viscosity I was after. Been running it for years and I often check the diff cover magnet for debris, and there's none.

That said, someone I know ran Valvoline full synthetic and they never could stop the limited slip from chattering. Was so annoying they swapped it out for conventional fluid and problem went away.

I dont think I've ever read or heard of anyone having differential problems because of the fluid brand they used. Lack of maintenance, abuse, and contamination are generally the cause of such things. So I agree...run whatever brand you want as long as it meets the specs for your application.
 

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Discussion Starter #9
Well, went with Valvoline, they only had 3 quarts of the Mobil 1 and I was not paying for the Royal Purple. Hopefully it works out. It had developed little shudder. Has not done it again yet🤞🏻
 

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Well, went with Valvoline, they only had 3 quarts of the Mobil 1 and I was not paying for the Royal Purple. Hopefully it works out. It had developed little shudder. Has not done it again yet🤞🏻
I always order mine from amazon, usually get the mobil1 about as cheap or less than locally sourced lesser brands.

Shudder? When?

Many with the limited slip, like mine, have a grinding, tightness after they get hot, during low speed tight turns.

Many, like mine, have been cured by the addition of the limited slip friction modifier additive, either as a separate tube of it added to the lube, or using the lube with the additive already in it. The limited slip in these trucks is a gear type, and normally don't require the additive, but it seems to help with this issue.
 

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Discussion Starter #11
Well, went with Valvoline, they only had 3 quarts of the Mobil 1 and I was not paying for the Royal Purple. Hopefully it works out. It had developed little shudder. Has not done it again yet🤞🏻
I always order mine from amazon, usually get the mobil1 about as cheap or less than locally sourced lesser brands.

Shudder? When?

Many with the limited slip, like mine, have a grinding, tightness after they get hot, during low speed tight turns.

Many, like mine, have been cured by the addition of the limited slip friction modifier additive, either as a separate tube of it added to the lube, or using the lube with the additive already in it. The limited slip in these trucks is a gear type, and normally don't require the additive, but it seems to help with this issue.
When backing up while turning or taking off with the wheels turning. Does it for a second or two then stops.
 

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When backing up while turning or taking off with the wheels turning. Does it for a second or two then stops.
Yes, exactly that.

Add the tube/bottle of limited slip additive to the gear lube and that will go away.
 

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I'm confused... I thought the 4th gen trucks have torsion differentials. :confused013: Friction modifier does nothing for those.
 

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I'm confused... I thought the 4th gen trucks have torsion differentials. :confused013: Friction modifier does nothing for those.
It's technically not REQUIRED, however some people are getting some chatter, especially warmed up, and it seems to help.
 

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It's technically not REQUIRED, however some people are getting some chatter, especially warmed up, and it seems to help.
How can it help? There's nothing but gears in there. No clutches for the friction modifier...
 

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Discussion Starter #16
When backing up while turning or taking off with the wheels turning. Does it for a second or two then stops.
Yes, exactly that.

Add the tube/bottle of limited slip additive to the gear lube and that will go away.
Is there a certain brand/type I need to use?
 

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How can it help? There's nothing but gears in there. No clutches for the friction modifier...
It's still modifying the fluid to make it more slippery for the torsen gears that are chattering? Just repeating what people have done, mine's an open diff so I don't have that issue.
 

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Make sure the seal on the bottle is intact before you leave the store. Some crooks pull return scams on oil by pouring something else in the bottle and getting a refund.
 

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