I have a 2004 S2000 AP2. I am having trouble on the track downshifting. It just does not let me engage. I am not talking about grinding. It just will not allow me to push the stick into gear! I never have this problem on the street. When I am hard braking from around 90-120mph, I try to downshift into 3rd at about 70mph or so. It just will not let me do it. I have to try several times before it will allow me to do it. By then, the turn is ruined! Is this a common issue with the AP2?

You can see me in this video struggling at turns 10a and 5 to downshift. It happens trying to downshift into 4th also. What's up?

(oh, don't make fun of my speed. I am doing the best I can )

http://www.youtube.com/watch?v=9Cxr34pb4WU



Jim

 

I can't really see what your talking about from the video but your problem is probably related to not rev matching.

Lucky guy to drive that track, I am going to make my way down there someday...

 

^^^That and it looks like you go from 5th straight to 3rd @ 1:17.....do you do that?
My car will not go into gear if I try to skip gears

 

Yes, at 1:17 5th to 3rd. Sometimes after the long straight I try to do 5th to 4th as an intermediate downshift and it still does not want to go in. It is like a hard lock on the linkage. I don't get it. I just keep trying and it eventually goes. I do rev match by the way.

Thanks,

Jim

 

In that case I don't know, I'm still an S2000 noob.

In my BMW (and AP1 from little experience) when I get the match right, the shifter literally gets "sucked" into gear, very little effort required.

 

If you don't skip gears does it still happen?

 

It has to do with your habit of skip shifting, and that has worn your syncros.

Before you downshift your engine is at one speed and your rear wheels are turning another speed.

After you downshift your engine will be turning faster.

As you put in the clutch the engine is disconnected from the transmission, but, the whole transmission keeps turning because it is still connected to the rear wheels.

As you move out of gear into neutral the front half of the transmission is no longer being driven by either the engine or the rear wheels, but, the back half of the transmission is still spinning with the rear wheels.

As you go to move into the lower gear the syncros spin up the front part of the part of the transmission to match the speed of the back half of the transmission and rear wheels, but, remember since you are going into a lower gear that front part of the transmission actually has to be sped up faster than it was moving before.

By skip shifting the syncro has to work even harder because the front part has to go much faster (2 gears worth) than it was before.

When you up shift this process occurs too and the front part is slowed down.

All of this speeding up and slowing down is done by your syncos, anytime you skip shift up or down you make the syncos work harder than they were designed to.

Do a lot of skip shifitng an you wear out your syncros and they eventually will need to be replaced.

note: I used front and rear of the transmission for illustrative purposes, there are actually shafts and gears in the transmission that are spun up and down.

also: rev matching really has nothing to do with this, unless you are also double clutching.

 

Good stuff TT.

But I thought if you matched the revs for the speed/gear you will be just fine on your syncros. In my track car I have done a mix of skip and, I guess regular "thru the gears" downshifting. I may have missed it in your explanation, but I am interested in hearing more.

 

Rev matching (without double clutching) mostly saves wear on your clutch and to some extent your engine and the drivetrain, as it is matching the speed of your engine to the speed of your transmission when you let out the clutch.

All the speeding up and slowing down of the 'halves' of the transmission while you are shifting is done by your syncros when your clutch is disengaged.

 

If his syncros were so worn out to cause this problem he'd be grinding gears all the time.

I have always skip-shifted on downshifts, regularly from 130mph in 6th down to 50 in second but I heel-and-toe to rev match. I have never had any syncro problems and no issues getting into a lower gear. TT, I do understand what you mean about part of the transmission being isolated on one end by the clutch and the other end by being in neutral.

I'm thinking maybe the clutch master cylinder may be going bad and allowing some clutch drag during the delayed down shift. OP, are you pushing the clutch in when you begin to brake and leaving it in until you complete the downshift? I do this to keep the ABS from fighting the engine during hard braking.