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Symptoms of bad synchro?

 
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Old 07-04-2010, 05:14 AM
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Symptoms of bad synchro?

Perhaps I am getting paranoid but I noticed that 1-2 and sometimes 2-3 gear feels notchy when the car has not been fully warmed up. Almost feels like there is some metal to metal friction. In addition, it's difficult to put the car in 1st gear unless I am almost to full stop. Are these signs of bad synchro? I don't have the typical grinding of bad synchro other than accidently grinded gears going from 1-2 and 2-3 because I didn't fully engage gear before releasing clutch. This happened at low rpm and was was for a brief second before I released the clutch. Just curious if I may have a bad syncho or other tranny issues? Can our cars take some amount of abuse such as intermittent gear grind?

Thanks so much for your help!
 
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Old 07-04-2010, 07:09 AM
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There is no synchro for 1st. It's always difficult to shift into unless you are at a stand still.
 
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Old 07-04-2010, 07:35 AM
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Originally Posted by sbkim View Post
Perhaps I am getting paranoid but I noticed that 1-2 and sometimes 2-3 gear feels notchy when the car has not been fully warmed up. Almost feels like there is some metal to metal friction. In addition, it's difficult to put the car in 1st gear unless I am almost to full stop. Are these signs of bad synchro? I don't have the typical grinding of bad synchro other than accidently grinded gears going from 1-2 and 2-3 because I didn't fully engage gear before releasing clutch. This happened at low rpm and was was for a brief second before I released the clutch. Just curious if I may have a bad syncho or other tranny issues? Can our cars take some amount of abuse such as intermittent gear grind?

Thanks so much for your help!
It is normal for a tranny to shift rough or not want to go into a gear when cold. My old STi had this issue more than any other car I owned.

The first gear while moving issue, you should be able to feel the tranny spinning some when your moving trying to put it in, that is normal, it will slow as the car slows. You will have to rev the car up (rev match) in order to place the car in first while going at a decent speed like 10-15 mph.
 
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Old 07-04-2010, 08:39 AM
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Thanks so much for your replies.

Quick update - I noticed that when I fully press on the clutch - all the way to the floor - the gear shifts easier.

I know this is a stupid question but do most of you guys shift when you have clutch depressed all the way to the floor???

Thanks again
 
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Old 07-04-2010, 09:58 AM
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First, you should adjust your seat so that when you push in the clutch, your knee is slightly bent. And yes you should always push the clutch all the way in. Second, if this doesn't solve your problem, it could be your shift linkage needs some adjustment. Check this before you start to think synchros.
 
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Old 07-04-2010, 11:48 AM
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Could be shifter cable adjustment issue. My 996c4s had that issue once.
 
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Old 07-04-2010, 01:13 PM
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Just out of curiosity what does defective or poorly adjusted shift linkage feel like? The car shift fine now that I am paying more attention to fully depressing the clutch
 
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Old 07-04-2010, 09:58 PM
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Your problem probably was not pushing in the clutch. Not pushing in the clutch all the way is asking for synchro problems. Balky shifting is the sign of linkage out of alignment.
 
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Old 07-05-2010, 05:31 AM
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Thank you landjet - again, when you say pushing in the clutch, you mean almost all the way to the floor, correct? vs. where it disengages?



Originally Posted by landjet View Post
Your problem probably was not pushing in the clutch. Not pushing in the clutch all the way is asking for synchro problems. Balky shifting is the sign of linkage out of alignment.
 
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Old 07-05-2010, 06:09 AM
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Yes, all the way in.
 
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Old 07-05-2010, 09:48 PM
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I"m experiencing the same thing, I shift with the clutch fully depressed, I live in the east coast so in the mornings the box does not like to shift up from 1st to 2nd and down shifts from 2nd to 1st. unless fully stopped, I had my shift linkage checked and they were within spec. My car has 9000 miles. I've asked many people and they say this is normal. On GT3s and Turbos.

For me, I've learned to be patient and if it is real cool outside, I blip the throttle before I put it in gear (up and down)

The other reason as I suspect, after checking out the factory fill specs for the box. Porsche is using some really low tech gear oil that was designed for long haul trucking, makes no sense to me! There are much better suited gear box oils with the latest additives package that will make a big difference in cold weather performance and hi temp protection. I will change out my gear oil in the fall, to Motul Motyl Gear 75W90. I know!! I'll probably get flame for not using Mobil products, I've work with many OEMs on their racing programs, and I'm going to go with what I know will work.
 
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Old 07-07-2010, 03:47 PM
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Originally Posted by bbywu View Post
There is no synchro for 1st. It's always difficult to shift into unless you are at a stand still.
1st gear has synchros. Always have and always will. Heck, these days, even reverse in syncrhonized. 41 is the 1st gear idler and 34,35, and 36 is the 3 piece synchronizer set.
http://dcauto.gotdns.com:4000/illust...index/36712962
 
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Old 07-07-2010, 03:55 PM
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Originally Posted by GTgears View Post
1st gear has synchros. Always have and always will. Heck, these days, even reverse in syncrhonized. 41 is the 1st gear idler and 34,35, and 36 is the 3 piece synchronizer set.
http://dcauto.gotdns.com:4000/illust...index/36712962
Matt, why does shifting into first require a complete stand still or a blip on the accelerator?

bob
 
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Old 07-07-2010, 04:11 PM
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It's because of the RPM drops between first and second, mostly. Out of all the gears, the rpm drop is the largest and differential in speeds of the shafts is the greatest as a result. First gear is really short, so either you've got to get way down in speed for the speeds between the two shafts to be matched, or you've got to spin up the output shaft faster to make them closer together in speed before the synchronizer can pull the parts to the exact same speed allowing a shift.

Say you are coasting at 20mph. If you had 1st gear engaged, your engine would be spinning at almost 3500rpm. So if you are in neutral and you want to downshift into that gear, you're going to have to spin your engine (and output shaft) up to close to that speed to synch it with how fast the pinionshaft is spinning. The synchronizers can only work within a certain range and if you go outside that range they aren't going to work.
 
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Old 07-07-2010, 04:13 PM
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Gotcha. I stand corrected.

Thanks Matt.

- bob
 

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