LSD gear oil? Help putting diff back together in a few hours.

[F34R]

Yeah this... What? You mean heavier oil is better for tracking your car? Regardless I went back to the speed shop today and they were pretty insistent on this being perfect for e30 lsd's so I think I'm going to go with it. Although I bought 75w90 today as well in case.

The owner of the shop is going to make a call to Motul for me to double check.

No thiner fluid is better for tracking because it has less internal friction. You have to change it more often though. This explains well: http://en.wikipedia.org/wiki/Viscosity

Whatever the case you will want thicker fluid for everyday use.

[Jaxx_]

No thiner fluid is better for tracking because it has less internal friction. You have to change it more often though. This explains well: http://en.wikipedia.org/wiki/Viscosity

Whatever the case you will want thicker fluid for everyday use.

[E30Rookie37]

No thiner fluid is better for tracking because it has less internal friction. You have to change it more often though. This explains well: http://en.wikipedia.org/wiki/Viscosity

Whatever the case you will want thicker fluid for everyday use.

That makes noooo sense. If I use thicker fluid then it will take longer to heat up and reach optimal viscosity and therefore mean for short drives that the oil is going to stay pretty thick. Which is why thicker is better because the 140 is meant for higher temps which you most definitely will reach at the track. At least that's my understanding and I think Jaxx's too.

[E30Rookie37]

No thiner fluid is better for tracking because it has less internal friction. You have to change it more often though. This explains well: http://en.wikipedia.org/wiki/Viscosity

Whatever the case you will want thicker fluid for everyday use.

That makes noooo sense. If I use thicker fluid then it will take longer to heat up and reach optimal viscosity and therefore mean for short drives that the oil is going to stay pretty thick. Which is why thicker is better because the 140 is meant for higher temps which you most definitely will reach at the track. At least that's my understanding and I think Jaxx's too.

[FredK]

While you may have slightly less loss to friction with a thinner oil, you're better off having the thicker stuff in your diff if you track it a lot. It is a torturous environment in there and the track is where the diff will heat up a lot, and you'll need the extra protection of a wider and higher viscosity range.

[E30Rookie37]

I put in the 75w140 and it seems to be working fine. Although I'm hearing a little chattering. And at 75-80 It makes a pretty audible whirring/whining noise...Any thoughts? I didn't add any friction modifier because I was told it was already in this oil i used..should I put some modifier in anyway? Anybody know what the issue could possibly be?

Other then that my car feels like it has a new engine with this newfound lower ratio.