rear end oil question
02-03-2009, 08:25 PM
#1
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rear end oil question The guy i bought my car from had swictched the rear end oil over to synthetic. i'm about to put a set of gears in it and i need to know which oil to put back in there. is anything going to be messed up because of the synthetic? will it be okay to go back to mineral oil?
02-03-2009, 09:19 PM
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nah i wouldnt think so either. but i've always been told not to switch from synthetic to conventional in your engine so i didint know if this applied to the rear also? i didnt know if it may do something to the posi unit or anything..
02-03-2009, 09:34 PM
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ya i wouldnt switch engine oil like that but with the rear, i wouldnt see a problem. im not for sure tho. just my guess. maybe someone else will chime in as well
02-03-2009, 09:40 PM
#5
Just put synthetic oil in it.
Its going to give you much better lubrication properties than regular gear oil, meaning less friction and heat, which wears out gears and bearings faster.
Can't go wrong with synthetic. I'd reccommend Mobil 1, Royal Purple, or Amsoil 75W-90.
Its going to give you much better lubrication properties than regular gear oil, meaning less friction and heat, which wears out gears and bearings faster.
Can't go wrong with synthetic. I'd reccommend Mobil 1, Royal Purple, or Amsoil 75W-90.
02-03-2009, 09:41 PM
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Just put synthetic oil in it.
Its going to give you much better lubrication properties than regular gear oil, meaning less friction and heat, which wears out gears and bearings faster.
Can't go wrong with synthetic. I'd reccommend Mobil 1, Royal Purple, or Amsoil 75W-90.
Its going to give you much better lubrication properties than regular gear oil, meaning less friction and heat, which wears out gears and bearings faster.
Can't go wrong with synthetic. I'd reccommend Mobil 1, Royal Purple, or Amsoil 75W-90.
02-03-2009, 09:44 PM
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02-03-2009, 09:48 PM
#9
However, GM and other companies require synthetics be used in their front differentials on the 4WD trucks and SUV's, as well as some rear differentials.
Its better, period. Theres no arguing that.
As to why Moser and Strange say to use regular oil, I have no idea, they would have to answer that one.
02-04-2009, 11:30 PM
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When I was looking to do my first gear oil change in my S60, i asked strange what was recommended, they said 80w90 non synthetic. I have also been told that some of these companies run synthetic oil in their rear ends in their race cars, so who knows.
02-04-2009, 11:41 PM
#13
Clutch type differentials work on friction, so using something that fights friction will hurt the performance.
There are no 4x4's that came from the factory with limited slip front diff so I'd guess thats why they recommend using it in them, and later (than '99?) f-bodies use torsen differentials (torque biasing--no friction clutches) so they came with synthetic also.
I've seen some newer type diff like Eatons with carbon fiber clutches say they can run synthetic, but then a few years after their release they say don't use synthetics.
If the car in question has an Auburn diff, use only mineral oil.
There are no 4x4's that came from the factory with limited slip front diff so I'd guess thats why they recommend using it in them, and later (than '99?) f-bodies use torsen differentials (torque biasing--no friction clutches) so they came with synthetic also.
I've seen some newer type diff like Eatons with carbon fiber clutches say they can run synthetic, but then a few years after their release they say don't use synthetics.
If the car in question has an Auburn diff, use only mineral oil.
02-05-2009, 03:10 AM
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The only issue with syn oil is with the carbon fiber clutches. The CF clutch discs used in the Eaton posi units will scream, moan and cry like a baby when used with synthetic lube even with the additive. For any other type of diff it is just fine to use and it will help with bearing and gear life.
02-05-2009, 10:29 AM
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Also, almost all synthetic engine oils are compatible with convention oils. That doesn't mean go mix them but changing from one to the other will not hurt anything.....
02-05-2009, 10:35 AM
#16
The only issue with syn oil is with the carbon fiber clutches. The CF clutch discs used in the Eaton posi units will scream, moan and cry like a baby when used with synthetic lube even with the additive. For any other type of diff it is just fine to use and it will help with bearing and gear life.
Now the instructions call for non synthetic.
And you cannot use synthetic in an Auburn.
Auburns use steel cone gears that go into powdered metal case inserts. Synthetic works best for preventing metal to metal contact, so if it's used in an Auburn it creates an open diff out of it. On the other hand clutch type diffs use fiber material that can tolerate synthetic oils better.
Why not just use what the manufacturer recommends? Their research and recommendations comes from hundreds of hours testing THEIR products. The consumers (us) research comes from "well my buddys car works fine with xxxxxx oil"
Go with who you trust knows the most about it.
02-05-2009, 10:54 AM
#18
Call Auburn and discuss with them why they do not recommend synthetic, and that your haynes manual says use it.
Auburn designed the diff, not haynes.
