Hi guys,

Searched around on the forum, but only found some (very) old topics.
I have an '01 S2000, already for about 10years driving it (and still in love) and now up to 115K kilometers (72K miles).
In the last year, I have some difficulties with the gearbox, having gears not shifting fluently/smoothly while driving. Sometimes it's rather hard to get the gears shifting, started with 5th gear but now also experiencing it in 3th-4th gear.
Changed the 'pivot' (plastic thing + new paste) under the shifter, no solution.
Changed the gearbox oil to Amsoil 'no friction', no solution.

I'm now thinking about changing/upgrading the gearbox to a facelift(AP2) gearbox to resolve the issue and, while at it, also placing a new clutch + pressure plate from an AP2, resolving the 'clutch buzz' thing.
First idea was to rebuild the transmission & synchros, but that would cost more in working hours and I'm not a DIY person myself to be honest
Replacing gearbox/clutch is a build out/build back in principle I think, with less working hours for an experienced guy. In the end, I see this as a proper upgrade for an AP1 model.

Good idea or crazy?

Thinking about parts needed:
- an AP2 gearbox (complete)
- an AP2 clutch & pressure plate
- an AP2 propellor shaft? A friend of me advised me to change this as well, since the propellor shaft bolt-on at the gearbox of an AP1 is not the same of an AP2 (8mm vs 10mm bolt on). I guess this is correct?

I'm a forgetting anything considering parts?

Any advise is very welcome, maybe from the owners that alread did this operation ?
Thank you!

 

The gearbox issues could just be caused by the clutch, but I have done exactly what you're suggesting and even though I now know that a simple clutch change would have fixed the car, its now got a stronger gearbox with better ratios.

 

So basically, what you are saying is that tough & un-smooth shifting (getting difficult in the gears) could be caused by the clutch? And by replacing clutch, pressure plate, etc the problem could be solved? (for instance to a newer or to an AP2 clutch)

But you changed gearbox to AP2 gearbox, AP clutch,..? Did you also replace the propellor shaft (between gearbox and diff) ?
Any other parts I'm forgetting?

 

Theres a chance yes. If the clutch isn't disengaging as it should, gear changes are going to be difficult. All I'm saying is before you write off the gearbox, look at the cheaper parts.

I don't think there is a difference in clutch between ap1 and ap2?

I didn't change my prop shaft.

 

You are correct in the bolts on the propshaft.. Atleast there is a difference I dont remember sizes. The easiest thing to do is to change the output flange on the trans, take your ap1 and put it on the ap2 trans.. Then you wont need to change the propshaft.

You can reuse the ap1 clutch and flywheel if wanted.. Im not sure what country you/your car is from but in the US, the ap1 flywheel is much lighter than the ap2 flywheel. The clutch disc and pressure plate are the same.

 

If its sticking in gears its your presser plate gone week but best to change the complete clutch all so get your clutch fluid looked at in case its dirty and needs changing or if its low. and if your clutch pedal is lower then normal get the clutch slave cylinder that operates the clutch checked for any leaks.

changing the gearbox wont make much difference its the clutch like the chap said above which is week unless your gear box is crunching in gears or making whining noses.

and if you are changing the gear box don't forget to match the ratio to your diff. or get them both together gearbox and diff from the same car. other wise it might end up costing you another gear box or the diff.

I don't really see any point you wont get much more out of it changing them. better clutch.

 

Where is your clutch's engage/disengage point, in relation to your pedal?

Does the clutch engage/disengage when the pedal is almost right at the floorboard? In the middle of its travel? Top of travel?

The crunchy shifting could be caused by a mis-adjusted clutch master cylinder or low master cylinder fluid level.

 

Thanks for replies so far guys

Gearbox is not crunching or making noises as far as I know/hear today. It's just not smooth shifting gears (going into the gear that is) from 3 to 4 or 4 to 5 by example. A gearbox making noises/crunching would be a sign of synchro problems?

About the clutch engage/disengage, what would be the normal point and what would be a signal that clutch/pressure plate/clutch master cylinder/... is end of life?
It's maybe worth a try to first replace the clutch completely by a new one. I was thinking (as said in first post) to replace the gearbox (due to synchro problem maybe) and while at it, also replacing the clutch completely. But thinking of that again, I would never know the real reason then probably.

If I understand everything correctly, the approach of most of you guys would also to be replace the clutch first then? An AP2/facelift model clutch and pressure plate is just 'bolt on' on an AP1/non-facelift gearbox? I would do that to get rid of the 'clutch buzz' in the meantime as well.

 

The internal gear ratios in 5th and 6th gears are different in the AP2 transmission as well as the primary and secondary reduction gears. The differential ratio is the same. I have no clue how to compare the numbers though! But they're different. I assume the speedo will be off.

This may be a clue: 3d gear in the two boxes is the same internal ratio (but the primary and secondary reduction gears differ). 3d gear my '06 (AP2) gearbox and speedo are nearly identical; 8000 rpm is almost exactly 80 mph. Not sure what rpm an AP1 runs at 80 mph. Or if this information is the least helpful.

-- Chuck

 

AP1 6-speed, close-ratio
Primary Gear Reduction - 1.160
1st gear - 3.133
2nd gear - 2.045
3rd gear - 1.481
4th gear - 1.161
5th gear - 0.970
6th gear - 0.810
Reverse - 2.800
Final Drive - 4.10 with Torque-Sensing Limited-Slip



AP2 6-Speed Transmissions Gear Ratios:
Primary Gear Reduction - 1.208
1st gear - 3.133
2nd gear - 2.045
3rd gear - 1.481
4th gear - 1.161
5th gear - 0.942
6th gear - 0.763
Reverse - 2.800
Final Drive Ratio - 4.100





Flywheels
Poids flywheel
AP1 = Approximately 14lbs
AP2 = Approximately 21lbs