Rear Differential Question
 

Nissan just replaced my LSD rear differential. They used Nissan synthetic
75W-140 gear oil. The book calls for 80W-90. (I think they use the 75W-140 in the GTR and Titan). Did they make a mistake or is Nissan recommending this weight now? Thanks for any input.

hmmm, well, I don't think nissan has changed out the specs for the diff fluid recently, so I'd lean towards the service tech putting in the wrong oil.

That said, I wouldn't worry too much about it. I'm actually going to be swapping rear diff fluid very shortly and will be running motul 75w 140 myself as per forged performance's recommendation since our rear diffs run so damn hot, esp under track conditons.

Did that in my WS6. Burned up the diff in 5K miles.

Axles and wheel-bearings went out, and pinion-bearing spun. The bearing was blue/rainbow from heat. I will never use any weight but spec, or Royal Purple again, for this reason.

It may all be coincidence, but I'm not going to do it anymore.

Royals Purple 75w90 working great here....

yeah, I'm actually agonizing over whether to make the switch to the heavier weight gear oil or not, got the two bottles sitting in front of me right now on the counter.

I personally think you had problems mainly cause you used royal purple, that stuff is crap. :p

still...


arrgggg....

I agree the stuff is crap, but it wasn't in there long enough to break down/shear/etc.

Like I said, too many variables to blame any one thing, I just know I won't do it again.

I would only go with the heavier weight if you are a serious track driver. The race track is the only place that would be able to get the 75-140 oil into it's proper operating range. The Viscous unit itself is sealed so the difference in oil weight has no effect on the limited slip.

So the Viscous is sealed? So what helps with the friction? Is there a oil or gel inside of it though? Can't remember.

Most viscous units use some kind of silicon based oil blend.

There is nothing that can be done to improve the stock viscous unit other than regulating temperature. If it gets too hot then the viscous fluid gets too thin, it won't work as effectively. Get it really hot and the silicon will start breaking down and lose it's effectiveness permanently.