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Discussion Starter · #1 ·
Hey guys,

gonna change the fluid in my rear diff tomorrow (Dana 35 stock limited slip). I know that with limited slip diffs you are supposed to use an additive. But my friendly neighborhood advanced guy said that in his guide you don't need it.

So my question is; what weight? And yes or no to the friction modifier?
 

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75W90 full syn. You do need the additive which will already be in the full syn. If I remember it will indicate that on the bottle.
 

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Discussion Starter · #4 ·
Ended up using 80 w90 conventional GL-5. With a 7Oz bottle of additive. Thanks for the responses and I probably wouldhave used synthetic, but I've read it doesn't transfer heat as well.
 

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What do you need the additive for?
I may be wrong, but you only need the friction modifier if you have limited-slip, which as far as I know yj's have open axles.
A lot of people put it in there to be on the safe side I suppose.
I use 80-90w gear oil on steeet driven or all around Jeeps, and 120w on my dedicated wheeling rig.
 

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d5 makes a good point. YJ's have open diffs unless yours was swapped out, but you indicated it was stock. Where did you read that conventional gear oil transfers heat better. All of the info. I've seen indicates the opposite between full syn and conventional. You're actually fine with either in the dif. In a manual trans., AX15 for example, it will shift/perform better with full syn 75W90.
 

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I used Valvoline 80w90 high performance in my d35 when I replaced the diff cover. No issues at all.
 
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