shifting from first to second weird

Synchros shot? Weird noises while shifting? Not sure what needs to be replaced?
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Re: shifting from first to second weird

Postby IMBoring25 » Wed Mar 02, 2016 5:09 pm

That's pertinent. Did you do the pilot bearing when you did the clutch?

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theholycow
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Re: shifting from first to second weird

Postby theholycow » Wed Mar 02, 2016 5:12 pm

Although I can't rule it out as impossible, I can't visualize a way that overextending could do that. However, I can imagine an internally leaking master cylinder that holds pressure through most of the stroke and only leaks at the end.
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Re: shifting from first to second weird

Postby Rope-Pusher » Wed Mar 02, 2016 10:12 pm

I would think that your car wouldn't be the only one doing this, but it could be that the clutch release system is over-stroking the release bearing. Maybe the diaphragm spring is intefering with the clutch disk when flexed too far and this keeps the clutch from freely spinning down during upshifts or spinning up during downshifts. If this is happening, it is either a mish-mash of parts that don't work well together, or something has broken that was meant to restrict the clutch pedal travel and it is now over-traveling.
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Re: shifting from first to second weird

Postby TakataDomeNSX » Thu Mar 03, 2016 6:00 pm

Yeah the 3 components of the clutch were changed. The clutch disk, pressure plate and release bearing.

I had a peek under the foot well today and the push rod from the master cylinder was fully extended. There was basically no more thread in the clutch pedal. If I were to turn the push rod any more it would basically disconnect from the clutch pedal. This weekend I might back it the other way a few turns and do some trial and error from there.

P.S. Is there a way of testing for a internally leaking master cylinder. I've tried holding the clutch pedal half way and seeing whether it sinks to the floor but it doesnt.

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Re: shifting from first to second weird

Postby IMBoring25 » Thu Mar 03, 2016 8:49 pm

Release (throwout) bearing and pilot bearing are not the same thing.

You can sometimes get a release system with an internally leaking master to work temporarily properly by pumping the pedal.

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Re: shifting from first to second weird

Postby Rope-Pusher » Thu Mar 03, 2016 11:52 pm

TakataDomeNSX wrote:Yeah the 3 components of the clutch were changed. The clutch disk, pressure plate and release bearing.

I had a peek under the foot well today and the push rod from the master cylinder was fully extended. There was basically no more thread in the clutch pedal. If I were to turn the push rod any more it would basically disconnect from the clutch pedal. This weekend I might back it the other way a few turns and do some trial and error from there.


THIS! You want to shorten the stroke of the master cylinder if the engagement / release points of the clutch are at pedal travel more than 35 mm up off the floor.
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Re: shifting from first to second weird

Postby TakataDomeNSX » Fri Mar 04, 2016 1:19 pm

In layman's terms whats going on if you have too much stroke? Thanks

Rope-Pusher wrote:
TakataDomeNSX wrote:Yeah the 3 components of the clutch were changed. The clutch disk, pressure plate and release bearing.

I had a peek under the foot well today and the push rod from the master cylinder was fully extended. There was basically no more thread in the clutch pedal. If I were to turn the push rod any more it would basically disconnect from the clutch pedal. This weekend I might back it the other way a few turns and do some trial and error from there.


THIS! You want to shorten the stroke of the master cylinder if the engagement / release points of the clutch are at pedal travel more than 35 mm up off the floor.

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Re: shifting from first to second weird

Postby Rope-Pusher » Sat Mar 05, 2016 5:38 pm

TakataDomeNSX wrote:In layman's terms whats going on if you have too much stroke? Thanks

Rope-Pusher wrote:
TakataDomeNSX wrote:Yeah the 3 components of the clutch were changed. The clutch disk, pressure plate and release bearing.

I had a peek under the foot well today and the push rod from the master cylinder was fully extended. There was basically no more thread in the clutch pedal. If I were to turn the push rod any more it would basically disconnect from the clutch pedal. This weekend I might back it the other way a few turns and do some trial and error from there.


THIS! You want to shorten the stroke of the master cylinder if the engagement / release points of the clutch are at pedal travel more than 35 mm up off the floor.

If you have too much release bearing travel, the diaphragm spring in the clutch cover will over-flex. What happens then is dependent on the design, but in some cases the spring may physically interfere with the damper in the hub of the clutch disk and make noise as it attempts to drag the clutch disk to rotate at engine speed, and/or the spring may over-stress from this extra flexing and eventually fracture.

I was supposing that this possible contact between the spring and the clutch disk was interfering with the ability of the synchronizers to spin the clutch disk up or down in rpm to the correct speed for the gear being selected. This could explain why the poster complained that the shifting was bad when the clutch pedal was fully depressed and not bad when the pedal was not fully depressed.
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Re: shifting from first to second weird

Postby TakataDomeNSX » Tue Mar 08, 2016 2:56 pm

That does make sense.

Any reason why it only occurs with 1st gear? Is it because it is triple or double synchro?

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Re: shifting from first to second weird

Postby Rope-Pusher » Tue Mar 08, 2016 6:57 pm

TakataDomeNSX wrote:That does make sense.

Any reason why it only occurs with 1st gear? Is it because it is triple or double synchro?

It would be about the clutch and the clutch release system - it really should be there for any transmission you use with it, but the ratio step between 1st and 2nd can often be big enough that it has the largest amount of work for the synchronizers to do.

I don't know if your Reverse gear is synchronized or not, but if your clutch were dragging while you tried to shift into a non-synchronized Reverse gear, you would hear about it. Even transmission with synchronized Reverse gear don't normally have high capacity synchronizers in this usage. They still might have very high shift efforts if the clutch was not fully releasing.
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