Thanks much for your thoughts and input. The fluid in the diff was silver...looked like mercury because there was such a high quantity of metal in it. So, maybe the original owner never changed it. It was a Wisconsin car and supposedly not driven in winter or bad weather. That's about all I know about it.

 

A word of caution for future. Some aspects of S maintenance are unique to the car. Its easy for a seasoned mechanic to assume they've seen it all and know what to do. Thats when critical errors can occur. Thankfully, our diff isn't one of those.

Other than knowing to replace the crush collar with carefully fit solid joint, all diff setup experience transfers.

Some of the things that are unique for future reference:

oil filter: needs some way to secure it from spinning loose, engine fire. Either a safety wire kit, or use the stock Honda filter, specifically the one with torquing instructions written on filter and numbers 1 - 8 at its base (used as torquing guide), AND TORQUE IT TO SPEC.

It may look ordinary, but in order to provide any resistance to spinning loose, needs to be torqued, and it is impossible to do by hand.

Any mechanic that doesn't want to hear it, says they know how to tighten a filter, never had one come loose, you need to run away from. Their hubris will be your cars undoing. They may be great, but they can still screw it up without knowledge.

If a non stock filter is used, or the regular one for other Hondas, DO NOT torque it down. Safety wire those.

The vibes from 9k rpm, and more importantly the very high oil pressure required by vtec, plus flow required for 9k rpm, is recipe for forcing filters loose. Many of these cars have been taken out by this. Burned to ground as oil spews onto hot manifold.

Another area is clutch. There are some unique tasks and steps that have to be done correctly or you'll soon have issues shifting smoothly.

Not a job anyone wants to do twice in a row.

So anytime your car needs maintenance, check in here first for the unique processes, then relay to mechanic.

 

Thanks much for these key tips! I never would have guessed there would be something unique about the oil filter change.

 

The OEM oil filter is a different design than most standard filters. The rubber sealing ring is sandwiched with 2 metal rings that make contact with the filter engine face. That is why the torque is important to keep the filter from moving under stress. Ordinary filters just have the rubber ring that gets compressed and does a good job for a Chevy or Ford. It can fit but not work for an S2000.

Both these filters fit but the one on the left is the OEM Honda filter and you can see how the rings are different. The one on the right is a quality K&N but has a standard rubber ring and that is it.

 

Academic, but I am unconvinced the metao rings purpose is to bottom out and make contact (you see galling on engine block filter housing surface if that were case).

Rather I think their presence is to prevent the gasket from distorting from the pressure of being torqued down so tightly. My theory is also that gasket shape is to prevent distortion as well. End result of clamping is gasket acts like an oring, an O shaped one, where sealing effect occurs from flattening the O shape.

Also, gasket rubber is much harder durometer than normal square gasket filter. So distorting it to flat shape takes more force.

The anti spin loose effect is then simply due to the clamping force exerted upon this very hard oring, and the amount by which its distorted.

Its a very unique filter design, that unfortunately looks quite ordinary. I wish it would have had a very different appearance, which would have been a trigger for everyone to recognize its unique and requires unique install. People would actually pay attention to its instructions.

Good engineering often requires thinking about the human element, and the psychology of behavior. Either that didn't happen here, or bean counters obstructed it.

My guess, they only realized this was an issue after initial designs were already inked. Original plan was use same filter as all other Honda's. A team was formed to come up with a solution that didn't involve redesigning anything on motor itself.

That automatically meant by default the filter interface would permit fitting standard Honda filter, whether they wanted that or not. Team was probably also told filter has to cost less than X. That meant creating something novel, whole new design, wouldn't be acceptable. Had to use existing filter manufacturing processes. That meant it was going to look like all other filters (in other words, bean counters won).