shawnhayes

iTrader: (2)

Ok, we all know synthetic fluids have SOME much better properties than conventional fluids.

In this light, when are all of you folks changing your transmission fluid and transfer case fluids and with what?

In the past, despite some warnings to the contrary (i.e. other drivers have cautioned me NOT to use them because they are TOO slippery), I have used synthetic fluids in my transmissions, with many, many, many miles logged with NO internal transmission problems.

The transmission and transfer case use very conventional fluid requirements, and Red Line sells several products that meet the gear oil requirements, and transfer case.

However, the REAR limited slip differential requests a certain Mitsubishi fluid (or "equivalent", as noted in the manual). Several manufacturers sell fluids for limited slip differentials (some of which are synthetic). Anybody have any thoughts on THAT?

Shawn

seattle944t

Mechanical LSD's require friction to work properly, unlike viscious (which are sealed with their own oils) or torque biasing Diffs. So synthetics DO pose a problem for the mechanical types. I am not sure what the specific oil that states for the diff, but it should display the weight of the oil.
And, as you mentioned, there are Synthetics that are desgned for LSD usage. These oils should work fine, or there are also "friction modifiers" that can be bought and added to any gear oil. But for example - RedLine offers two versions of their gear oil, as well as a spererate friction modifier fluid:

http://www.redlineoil.com/redlineoil/gearolti.htm#75W90

75W90 Gear Oil - the preferred product in nearly all car and light truck differentials, both conventional and limited-slip. 75W90 is preferred for most racing applications. It contains friction modifier which is recommended for limited-slip units. 75W90 Gear Oil can be used in many transmissions and transaxles; however, other Red Line lubricants have better frictional properties for rapid synchronization. Exceeds API GL-5.

75W90 NS - a GL-5 which does not contain the friction modifiers for limited-slip hypoid differentials. This makes the transmission synchronizers come to equal speeds more quickly, allowing faster shifting and much easier low-temperature shifting. Can also be used in racing limited-slip differentials where weak spring design causes too much wheel spin.