Just got my gears/Auburn LSD installed. The installer told me synthetic is the worst thing I could do to this Auburn LSD. Apparently it will cause it to not lock-up (he has an Auburn, used synthetic and destroyed it). I'm not gonna argue with that! Can anyone validate this?

Regardless, I'm taking his word for it, because even if he is wrong, its not worth destroying it to save .5 mpg at best.

That being said, whats the best NON-synthetic out there?

btw, I still plan on using synthetic in the front, since theres no posi up front, and it takes different weight anyway...

 

ya know...i used synthetic in the rear diff in my truck with the Auburn LSD and never once had any problems with it....but as for the best non synthetic....if i had to run a non synthetic, i'd prolly run Lucas really

 

That's what I do, run Lucas in the rear and change it every 15k, Royal Purple in the front and change it every 30k.
I got into it pretty heavy on the phone with someone at Auburn Gear after I got mine. I was told by 4 Wheel Parts that I could never put a synthetic in there as well.
I decided to investigate just why, and emailed Auburn. The reply I got was basically, "because we say so", which really pissed me off. In the guy who replied's signature on the email, it listed the phone number and ext. of the guy. So I called, wanting to know "why they say so". I never really got a reason, but was told if the unit failed during the warranty period and it was determined that a synthetic was used, the warranty would be void. To date, I still have never been given an exact reason why you can't use a synthetic. I make it a point to ask at auto shows where they have a booth and usually can't get an answer either. When I do get one, you can tell it's BS the idiot is making up on the spot to not look stupid. At the Orlando show last summer, the guy at the Auburn Gear booth was at least honest, he said "Yo dude, they just pay me to sit here and pass out these fliers and T-shirts. Last week I was handing out stuff in Jacksonville for Jet power modules". Every employee of Auburn is aware you can't run a synthetic, but nobody can tell me why...

 

Its something to do with the friction capability. I have know idea about rear ends, but, in race engines with roller rockers, you are not ment to use synthetic oil as the rollers dont roll. !!! The oil is to slippery and so instead of rolling and moving with the lifter and rocker, they just sit there rubbing and put a flat on it.
It must be something like that. !!

 

The critical thing in a differential, because of the interface of the ring and pinion gear being a hypoid or spiral bevel, is the requirement for a GL-5 gear oil. GL-5 has extreme pressure additives to protect the gear teeth as they mesh because there is a sliding motion and they are highly loaded.

Viscosity has far less to do with it. And the limited slip has nothing to do with it either. In fact, many limited-slip units that employ clutches such as the Auburn recommend conventional oil over synthetic because the clutches tend to operate (hold and slip) better.

 

I run royal purplw with my auburn... never noticed anything bad? the shop I got it done at reccomended switching over to royal purple....

 

so is this the case with just auburn? or any diff?

 

just auburn as far as i know....haven't ever heard of any other companies requiring use of non-synthetic gear lube

 

I just had the $tealer$hip do my 30K on the diffs, and synthetic was recommended by Dodge.

 

Yes it is, but do specifically own an Auburn Gear LSD?