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Originally Posted by Bigsalgt,Sep 2 2004, 05:30 PM
When it comes to FWD and RWD, its a whole other ball game! In my GS-r, I NEVER replaced the case fluid and that car was subject to more races then any other car I have owned. I have noticed though that the S2 is so much more tempromental then many other cars. This of course is due to its great characteristics that make it an S2000. Best advice for this topic is every 15k if your driving it more then avearage.
Or more often if you do it yourself. A diff fluid change is really cheap for a DIY'er.
The best diff fluid in my opinion is the Lubrication Engineer's LE 607 with Almasol that is available through the "Go Fast Lab" in the S2Ki marketplace.
As a rule, I change my differential and transmission fluid during every other oil change (i.e., every 6K) or twice a year (if my mileage is low). Though it may seem like overkill, the performance results and peace of mind are worth the extra few dollars.
Generally, moly is not used a lot in differential lubes of which I am acquainted. It was new sulfur compounds which are the EP additives in nearly all modern diff lubes that alllowed GL-4 to go to the higher capacity GL-5 spec. Plus, they give that heavenly gearhead perfume we all know and love - the gear lube "aroma". When I do a fill on one of our cars with rear diffs, my wife makes me march straight to the washing machine and do a "solo" wash run while holding her nose and going "pewww"! It is as steady as the sunrise.
The LE607 I have recommended uses a unique aluminum magnesium silicate additive, which has even better properties than moly or the sulfurs commonly used, although they also use sulfur. It is proprietary to Lubrication Engineers, and sold by their additive subsidiary as Almasol. Supposedly, it is used as a dry lubricant as well on spacecraft. Hopefully, ours, not the Independence Day lobster/octopus baddies.
Originally Posted by rufusrevs,Sep 2 2004, 12:27 PM
(No 'dropped clutch' standing starts, or full throttle at low rpm in my S2000....any guesses what would happen on garden variety Accords and Civics if drivers treated them that way?)
ummm.. Full Throttle at Low RPM is not good?? could someone plz explain this for me???
The thing that's odd to me is when I changed my diff lube at 11,000 miles, the oil was not that dirty and there were very little crud on the drain plug.
Tribology - the science of bearing lubrication, says that the load a bearing is capable of carrying while still maintaining an oil film between moving parts is based on lubricant viscosity, bearing geometry, shaft speed, etc. If the load is too great at too low an rpm, the oil film is squeezed out and metal to metal contact occurs. Similarly, if the same can happen if the oil viscosity is too low.
An analogy is a car driving too fast on a water covered road and hydroplaning. But, in the case of a bearing hydroplaning is good. With a loaded bearing you want the rpm to be fast enough so the hydrodynamic wedge of oil will support the load and 'hydroplane', thus preventing wear cased by metal to metal contact.
Note that most all car manuals show minimum recommended shift point for cars with manual transmissions........for exactly this purpose. To prevent 'lugging' the engine and overloading the bearings at low speeds.
Honda's shift recommendations for the S2000 are:
Shift mph Rpm after shift (approx.)
I - II 15 2086
II - III 25 2518
III - IV 40 3158
IV - V 47 3110
V - VI 52 2868
These numbers were calculated based on raod test data published in Car and Driver and Road & Track magazines for 2003 S2000's.
Back to bearing loads and wear, if one follows Honda's suggested minimum shift points, the engine speed will never drop below 2000 rpm, except in 1st gear. They are saying these are the minimum recommended shift points for normal driving (i.e. gentle acceleration). Heavier acceleration at these speeds will apply greater loads and possibly overload the driveline bearings.
Therefore, I wouldn't floor it until at least 2000 rpm in my S2000. In 1st gear thats about 9 mph.
Another comment on diff fluid viscosity. I'll be the first to agree that Mobil 1 is good. I'm a stockholder, and use it in all but one of my cars. However I question how someone knows it's ok to use Mobil 1 75W - 90 in the S2000 diff. The SAE 90 gear oil recommended by Honda and 75W - 90 will have the same viscosity only at 100 C (212 F). At lower temps the 75w - 90 has a lower viscosity. Unless we know that the typical operating temperature of the diff fluid in the S2000 is around 212 F, then changing to 75w -90 will result in a different viscosity under typical operating conditions. If the operating temp is lower than 212F, then the viscosity will be lower, bearing load carrying capabilities will be lower and increased wear may result.
Back to my original point......If you don't know for sure, either by being a Honda engineer, or by intrumenting diff temps, deviating from the service manual recommendations carries a risk.
Any Honda engineers out there? Anyone got readings on their diff oil temp? Next time we have a 90F day, I'll drive my car at 60mph for a while and put a hand on the diff to get a subjective feel for how hot it gets.
