Searched around didn't find much on this subject. My S2000 is a 2001 with 38000 miles. In the last 6 months or so I've noticed that it takes a strong arm when shifting out of 2nd gear for the about 10 minutes of driving. After that it shifts fine. The problem is getting worse with time so I'm starting to get a bit concerned. Sometimes it feels like it just locked. I'm using Mobil 1 75w 90 synthetic transmission fluid last changed at about 9000 miles.
Any idea what the problem could be?
Thanks

 

All S2k's don't like to be shifted fast when cold. Been like it since 00, every one I've ever PDI'd or driven doesn't shift smoothly cold. Changing the trans fluid regularly helps, but your 75w90 probably isn't helping the cold shifting. OEM Honda MTF is much cloer to a 10w30 motor oil.

Get the right fluid in the trans and see if that helps you out.

 

my friend had the same problem for a while, and yesterday he couldnt get it into gear at all, the pressure plate is done, once u have those symptoms, thats when u know its the pressure plate.

 

When a clutch breaks and doesn't disengage, the trans shifting doesn't get any better after driving. It's always almost impossible to shift.

 

Are you sure you aren't using 75w90 Synthetic GEAR OIL? That's GL5 and is extremely harmful to the brass syncronizers found in the AP1 transmission. I would get that stuff out of there ASAP and do a couple of flushes with some new formulation Honda MTF. 4 quarts of the new MTF will run you about $20.
Put the first fill in your car and run it for 600 miles or so, then drain it and refill again and leave the MTF in there for a longer period of time.

 

my 2-3 shift is always a little 'notchy' when cold. try changing the transmission fluid to Redline MTL. that seemed to help a lot with mine. but once the gearbox warms up its butter smooth!

 

I agree. The Mobil 1 synthetic 75w 90 stuff is GEAR oil. Copied straight from mobil1 website:

" Mobil 1

 

Yeah man, the Mobile 1 75w90 is for the differential, not the transmission. if that's in your manual gear box you need to get it out now, don't even drive the car any more.

 

IMO there are gears inside a transmission so a gear oil should do fine
But not a gear oil with sulphur, and that mobil 1 has sulphur in it IIRC from posts about it (the mobil 1) stinking to high heaven. (rotten egg)

If a brass synchro is damaged or eaten away by the sulphur, IMO it would be hard to get into gear, not out of gear?
Or did the OP mean out of 2nd into 3rd?
If that "sulphur oil" has been used there may be damage to the synchro's by now.
But I remember a post about someone having that kind of oil in their transmission for a long period without any problems.

About the viscosity...
SAE 75W-90 gear oil and SAE 10W-30 engine oil can not be compared just by looking at the numbers.
For gear oil look at SAE J306 spec, for engine oil look at the SAE J300 spec.
The MTL-P transmission (gear) oil is 75W-85 and works very well in my transmission (gearbox)

That oil has been in there for 9000 miles, time for a change IMO.