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-   -   crunching sound sometimes when changing into second gear (http://986forum.com/forums/boxster-general-discussions/36636-crunching-sound-sometimes-when-changing-into-second-gear.html)

tobiasr 08-03-2012 12:40 AM

crunching sound sometimes when changing into second gear
 
Since i bought the car a year ago, second gear has always been a harder to get then the rest, and now recently it has made a crunching sound when downshifting to second a couple of times.

What can be done to make it smoother? Going to change my clutch next spring since my mechanic says ins worn, can that fix it or do i have to change something in the gearbox to make it smother?


986 manual from 199

Bruce Wayne 08-03-2012 12:52 AM

when was the gear oil changed ?

does it only happen when cold or when hot too ?

is there any sign of clutch slip ?

Ghostrider 310 08-03-2012 02:17 AM

No matter what else you do, stop downshifting immediately, if it's a synchronizer continuing to do so will stress it further.

tobiasr 08-03-2012 03:15 AM

Quote:

Originally Posted by Bruce Wayne (Post 300123)
when was the gear oil changed ?

does it only happen when cold or when hot too ?

is there any sign of clutch slip ?


Gear oil was changed a year ago, only head the sound when i have been driving for a while. Not really sure what clutch slip is, how do i know if i have that?

Bruce Wayne 08-03-2012 03:44 AM

Quote:

Not really sure what clutch slip is, how do i know if i have that?
stop on the flat and look to pull away slowly in second gear. if the clutch is worn it will start to slip, you'll see the rpm rise quicker than the speed increase.

to be honest, a worn clutch shouldnt grind the gears as the clutch, in essence, disengages the drive between gear changes. a worn clutch will slip, ie the drive plates will slip against each other, so the engine rpm will increase will the road speed does not.

a worn thrust bearing will give a 'humming' noise through the clutch depression and release cycle.

my initial thought as it seems ghost rider's was is a failing synchromesh. just one thought.. make sure your mat is out the way and the clutch pedal is going right down.. could really be that simple.


if the syncgromesh is on the way out (i had it happen on a car a few years back as a plastic retainer had broken and smeared up the sychromesh ring, making it stick up) then be gentle with the gearbox and gear changes and either consider having your box o/h, an exchange item or replacing it..

its not *all* bad news if that is the case, it gives you the opportunity to consider having the RMS and IMS changed as the gearbox is going to come off so you're 99.9% of the way there anyway !!

opus69 08-03-2012 04:18 AM

2nd gear issues
 
I had similar issues with 2nd gear grinding if I was not very careful (2002 S 42,000mi). Occasionally it would also pop out of 2nd. I am not sure exactly what solved the problem. I may just be more careful, but I replaced the 2nd gear detent (2ND GEAR POP-OUT UPGRADE-GBOX Transmission) and it hasn't popped out since. I also recently replaced the clutch and flushed the hydraulics. Although I love to downshift, I took someone's advice (on this forum) to use the brakes more since they are much cheaper to replace, rather than always downshifting.

Bruce Wayne 08-03-2012 05:10 AM

i dont downshift that much as i dont like putting the additional stresses though the engine, transmission and drive train; then again i don't use the boxster as a track car with the joy of having the capability to perform rebuilds.

as i'm 6'3 i'm not big fan of heel and toeing either as invariably there are few cars that i can move my legs and feet about quickly in.

personally, i find with the boxster it seems to pace quicker keeping the car in the lower to mid power band and using the available torque by keeping a good line into the curve finding the correct roadspeed and to power though the bend

if i find i'm downshifting lower than third its probably because either i've ballsed up the entry or i'm driving outside the conditions of the road and it wont be a comfy well paced run but harsh, jerky and likely to wear the shoulders of the tyres down quickly :mad:

what i try and do is to take the principles of energy management from aviation into fast paced driving, here is a short clib of the great Bob Hoover demonstrating engergy management (dead stick)

Stopped engine aerobatics - YouTube

Overdrive 08-03-2012 06:41 AM

My grind happens when shifting from 1-2 if I do it too quickly, so I force myself to take my time and ease the stick into 2nd gear, even when autocrossing, and it's only a very occasional thing. How often does this happen to you? Every downshift?

Bruce Wayne 08-03-2012 07:30 AM

nope never had a crunch between gear changes. i did change the gear oil not long ago and the box it a little 'tighter'.

the other point i make with the car is that i keep the rpms below 3,000 until it has reached operating temperature.

san rensho 08-03-2012 07:33 AM

Sounds like the synchro is second is going. If you learn to rev match double clutch, you will get smooth downshifts and the transmission will last forever.

Uller God 08-03-2012 08:38 AM

tobiasr, at what RPM are you shifting from first to second? The sweet spot to match rev/syncro seems to be around 3K. If you hit that spot you won't even need to use the clutch and it will fall right into gear. Try double clutching when going from third to second.

Topless 08-03-2012 08:56 AM

Sounds like a worn synchro. Shifting gently will extend the useful life of your trans but at some point you will probably need a "trans"plant. :) Attempting to carry 3rd gear through every 90 degree right turn is not a very interesting way to drive this car.

Ghostrider 310 08-03-2012 09:30 AM

Quote:

Originally Posted by Uller God (Post 300175)
tobiasr, at what RPM are you shifting from first to second? The sweet spot to match rev/syncro seems to be around 3K. If you hit that spot you won't even need to use the clutch and it will fall right into gear. Try double clutching when going from third to second.



I have to tee hee a bit on this one, a maneuver like this works better on a 1964 VW bug than on a Boxster. Miss by a little and you will be parked shortly afterword.

Overdrive 08-03-2012 12:52 PM

Quote:

Originally Posted by Bruce Wayne (Post 300155)
nope never had a crunch between gear changes. i did change the gear oil not long ago and the box it a little 'tighter'.

the other point i make with the car is that i keep the rpms below 3,000 until it has reached operating temperature.

Owner's manual says to keep the RPMs below 4000 until the car reaches operating temp. The general concensus around here is that these cars like to be above 3000, so your best bet is to drive and shift in that 3-4k range. Below 3k these cars are not happy, even when they're cold.

Bruce Wayne 08-03-2012 04:03 PM

nice catch overdrive, that'll teach me for not checking for typo's befor i post.

i tend to go no higher than 3500 till warm and the engine and transmission seem very comfortable with that

tobiasr 08-06-2012 01:59 AM

Thanks for all the answers.

I have no idéa how to dubble clutch, is there any good guide on how to do that? If i have to replace the transmission or repair it, what would that cost?

I usually change from first to second on about 3k to 4k rpm, sometimes when racing its on the redline.

The crunch sound has happened perhaps 5-6 times in a year, but it is always hard to shift 1 to 2, or 3 to 2. No difference if the car is hot or cold.

Ghostrider 310 08-06-2012 03:15 AM

You're going to need transmission work or replacement, no clutching changes will heal the synchronizer, it will simply prolong the time you can wait till repair. As far as double clutch, we had a 1936 Simca, generally speaking, one clutch action from gear to neutral then a second clutch action from neutral to gear.

san rensho 08-06-2012 08:54 AM

Quote:

Originally Posted by tobiasr (Post 300449)
Thanks for all the answers.

I have no idéa how to dubble clutch, is there any good guide on how to do that? If i have to replace the transmission or repair it, what would that cost?

I usually change from first to second on about 3k to 4k rpm, sometimes when racing its on the redline.

The crunch sound has happened perhaps 5-6 times in a year, but it is always hard to shift 1 to 2, or 3 to 2. No difference if the car is hot or cold.

Double clutching is used on the downshift only. The procedure is roughly as follows: let's say you are in third gear and want to downshift to second. You put the clutch in and go to neutral, let the clutch out, and with the clutch out, blip the throttle to get the RPMs up, then quickly press in the clutch and put it into second gear. It takes a bit of practice but after a while it will be second nature.

When shifting up, from first to second, I get the smoothest shifts using the following procedure: right before I shift, with the clutch still out, I apply slight pressure to the gear shift knob in the direction of second. As I hold the pressure on the gear shift, I push in the clutch and continue to apply the same pressure and the transmission goes seamlessly into second.

Overdrive 08-06-2012 10:30 AM

The method san rensho described is basically what I do any time I do downshift, minus the release of the clutch before the shift. I'm able to put the clutch in, do a rev match while downshifting, and let the clutch out. Other than sometimes not getting the revs quite right, I've never had a problem.

Ghostrider 310 08-06-2012 11:58 AM

Other than sometimes not getting the revs quite right, I've never had a problem.




That's like taking a handgun course and saying, "other than occasional flesh wounds". You only get a certain number of "grinds" loose a few teeth and watch the problems begin and quickly.


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