Need help diagnosing a nasty shifting noise/5 speed
08-04-2002, 03:55 PM
#1
Racer
Thread Starter
Need help diagnosing a nasty shifting noise/5 speed
High,
On a high rpm shift from 2nd to 3rd I get the nastiest sounding quick grind going into 3rd. It did it once last sunday, so I thought I just made a sloppy shift, but this week on my way home from a 250 mile rip, it must have happened 20 times, 2nd into 3rd. I dont think I,m being sloppy because I haven't miss shifted 20 times in the last 5 yrs never mind 1 week. It will take a SLOW shift up to 6000, but anything higher or faster and I get the sound.It appears to happen when the engine is hotter, because it wasnt doing it in the early morning. I have an andial semilight weight flywheel/clutch that was Installed 10000 miles ago and havent had any problems w/ it. Is this a syncro problem? How much is a repair like that cost and how long does it take? any advise or input is apprieciated, thanx, Geo.
On a high rpm shift from 2nd to 3rd I get the nastiest sounding quick grind going into 3rd. It did it once last sunday, so I thought I just made a sloppy shift, but this week on my way home from a 250 mile rip, it must have happened 20 times, 2nd into 3rd. I dont think I,m being sloppy because I haven't miss shifted 20 times in the last 5 yrs never mind 1 week. It will take a SLOW shift up to 6000, but anything higher or faster and I get the sound.It appears to happen when the engine is hotter, because it wasnt doing it in the early morning. I have an andial semilight weight flywheel/clutch that was Installed 10000 miles ago and havent had any problems w/ it. Is this a syncro problem? How much is a repair like that cost and how long does it take? any advise or input is apprieciated, thanx, Geo.
08-05-2002, 06:26 AM
#3
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This problem is not uncommon if the gearbox/transmisison is really hot. I may suggest as Christer says, that you need to check your transmission fluid levels. Actually I would seriously consider, draining the fluid and filling with nice new stuff. This does I promise make the world of difference,
Ciao,
Adrian
911C4
Ciao,
Adrian
911C4
08-05-2002, 04:45 PM
#4
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Hi Geo,
Any problems downshifting from 4th to 3rd? Have you tried double-clutching to match RPMs? I suppose your super-quick shift might match RPMs pretty well on an upshift. Also, it might be a bit too tricky, considering that you're only having the problem at close to redline. Anyway, the idea is to try and remove the sychros "from the equation," as they don't do any work when RPMs are matched.
Here are some interesting links that might give you some insight to what's happening inside your transmission:
<a href="http://www.howstuffworks.com/transmission3.htm" target="_blank">How a Manual Transmission Works</a>
<a href="http://www.g-speed.com/pbh/double-clutch.html" target="_blank">Double Clutching</a>
Maybe it's time for that 993 6-speed, preferably the G50/21.
Okay, seriously, here's hoping a change of gear oil will cure your problem.
Any problems downshifting from 4th to 3rd? Have you tried double-clutching to match RPMs? I suppose your super-quick shift might match RPMs pretty well on an upshift. Also, it might be a bit too tricky, considering that you're only having the problem at close to redline. Anyway, the idea is to try and remove the sychros "from the equation," as they don't do any work when RPMs are matched.
Here are some interesting links that might give you some insight to what's happening inside your transmission:
<a href="http://www.howstuffworks.com/transmission3.htm" target="_blank">How a Manual Transmission Works</a>
<a href="http://www.g-speed.com/pbh/double-clutch.html" target="_blank">Double Clutching</a>
Maybe it's time for that 993 6-speed, preferably the G50/21.
Okay, seriously, here's hoping a change of gear oil will cure your problem.
08-06-2002, 01:44 AM
#5
Racer
Thread Starter
High,
Thanx Guys, I havent had any problems going down from 4th to 3rd, but I appreciate the links Randall, very interesting. As Adrian states this is not uncommon when the trans is really hot, I would say my trans was really hot(at least 250 hard miles through the mountains, with only about 20 mins. rest all morning, and the temp was above 90 degrees on the way back home). I'll do as Adrian and Christer suggest and ck my gear oil level and most likely change it, my records indicate a change at 28600 miles,some 8000 miles ago, but i'll do it again anyway just to be safe and let you know the results, one more quick question; where do you check the gearbox oil from? thanx again gentlemen., George. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
Thanx Guys, I havent had any problems going down from 4th to 3rd, but I appreciate the links Randall, very interesting. As Adrian states this is not uncommon when the trans is really hot, I would say my trans was really hot(at least 250 hard miles through the mountains, with only about 20 mins. rest all morning, and the temp was above 90 degrees on the way back home). I'll do as Adrian and Christer suggest and ck my gear oil level and most likely change it, my records indicate a change at 28600 miles,some 8000 miles ago, but i'll do it again anyway just to be safe and let you know the results, one more quick question; where do you check the gearbox oil from? thanx again gentlemen., George. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
08-06-2002, 03:25 AM
#6
Geo:
Aside from what's been mentioned, you may want to also consider checking the clutch for complete engagement and disengagement. Such a problem could be caused by a failing clutch or a hydraulic problem (fluid, slave cylinder, etc). Since you have a new flywheel, I assume you either have a new clutch too or yours was not old enough to warrant replacement. Synchros could be problematic, but appear to be pretty rare on these cars (unless they have tons of miles).
A way to test the clutch engagement is to take the car to a level, open (no cars around), flat and LEVEL area (like a parking lot). Push in the clutch pedal, put the car in 1st gear, and while holding the clutch pedal in, start giving the car gas (enough for say 4000 - 6000 RPM). If the car starts creeping forward, then your clutch is not disengaging completely.
If you decide to change the tranny oil, I would go with Mobil 1 synthetic. When I first bought my car and had everything changed, I let them swap out the Mobil 1 that was in there with dino thinking it wouldn't be a noticeable difference. I was wrong. When I do my next full service the dino is going out and Mobil 1 is going back in.
Hope this helps.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
Aside from what's been mentioned, you may want to also consider checking the clutch for complete engagement and disengagement. Such a problem could be caused by a failing clutch or a hydraulic problem (fluid, slave cylinder, etc). Since you have a new flywheel, I assume you either have a new clutch too or yours was not old enough to warrant replacement. Synchros could be problematic, but appear to be pretty rare on these cars (unless they have tons of miles).
A way to test the clutch engagement is to take the car to a level, open (no cars around), flat and LEVEL area (like a parking lot). Push in the clutch pedal, put the car in 1st gear, and while holding the clutch pedal in, start giving the car gas (enough for say 4000 - 6000 RPM). If the car starts creeping forward, then your clutch is not disengaging completely.
If you decide to change the tranny oil, I would go with Mobil 1 synthetic. When I first bought my car and had everything changed, I let them swap out the Mobil 1 that was in there with dino thinking it wouldn't be a noticeable difference. I was wrong. When I do my next full service the dino is going out and Mobil 1 is going back in.
Hope this helps.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
08-06-2002, 06:29 AM
#7
Race Car
George, this is very common in a HOT G-50 with considerable mileage on them. Mine does it all the time at the track, but I can't seem to get it hot enough to reproduce the symptom on the street.
BTW, my gearbox has 67K on it.
Changing the gearlube will likely NOT fix the problem as it is a mechanical problem, not an issue of lubrication. I changed from whatever was in there to Mobil-1 and it didn't change a thing.
I have several friends that experience the same thing in their G-50 equipped P-Cars, one is a 968, the others an '86 Carrera and a couple of 964s.
It's just wear and tear, it's likely your synchros are worn.
My advice - live with it...it won't cause anything catastrophic...it will just continue to wear and become an issue SEVERAL thousand miles from now.
...by that time there will be other transmission issues that will warrant a rebuild.
BTW, my gearbox has 67K on it.
Changing the gearlube will likely NOT fix the problem as it is a mechanical problem, not an issue of lubrication. I changed from whatever was in there to Mobil-1 and it didn't change a thing.
I have several friends that experience the same thing in their G-50 equipped P-Cars, one is a 968, the others an '86 Carrera and a couple of 964s.
It's just wear and tear, it's likely your synchros are worn.
My advice - live with it...it won't cause anything catastrophic...it will just continue to wear and become an issue SEVERAL thousand miles from now.
...by that time there will be other transmission issues that will warrant a rebuild.
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08-06-2002, 12:29 PM
#8
Racer
Thread Starter
High,
Thanx again, I will take ALL the advice above,
1. ck the level of gear oil
2. replace gear oil w/ mobil 1
3. ck clutch engagement
4. if all else fails, live w/ it for now.
Keep you posted, Peace Out, Geo.
Thanx again, I will take ALL the advice above,
1. ck the level of gear oil
2. replace gear oil w/ mobil 1
3. ck clutch engagement
4. if all else fails, live w/ it for now.
Keep you posted, Peace Out, Geo.
08-07-2002, 03:55 AM
#9
To some extent I'm going off topic, but when I let the shop that did my initial PPI and complete service change from the existing Mobil 1 to Dino, the shift effort was noticeably higher. I didn't really do this deliberately, it was more like a mis-communication between me and the guy writing up the work order, which was my fault.
I'm not suggesting that a change in oil is going to fix your problems since the cause hasn't been identified, I've just noticed in the cars that I've owned (2 with Getrags) the shift effort was noticeably lower with Mobil 1. It's a good (maybe I should say excellent) oil and it can stand up to heat better than dino.
Hell, if I'm wrong, please shoot me!
<img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />
I'm not suggesting that a change in oil is going to fix your problems since the cause hasn't been identified, I've just noticed in the cars that I've owned (2 with Getrags) the shift effort was noticeably lower with Mobil 1. It's a good (maybe I should say excellent) oil and it can stand up to heat better than dino.
Hell, if I'm wrong, please shoot me!
<img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />
08-07-2002, 04:53 AM
#10
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Dear Bill,
I fully support what you say. Just ask my daughter. When I gave her the 944 her main complaint (apart from no power steering) was that the gear changing was hardand it whined. I test drove the 944 and agreed.Now we did not use Mobil 1 because we could not get it. We replaced the transmission oil with Castrol GTX fully synthetic. It was like driving a new car. The whine was almost gone, the gear changing was much smoother and much easier.
Ciao,
Adrian
911C4
I fully support what you say. Just ask my daughter. When I gave her the 944 her main complaint (apart from no power steering) was that the gear changing was hardand it whined. I test drove the 944 and agreed.Now we did not use Mobil 1 because we could not get it. We replaced the transmission oil with Castrol GTX fully synthetic. It was like driving a new car. The whine was almost gone, the gear changing was much smoother and much easier.
Ciao,
Adrian
911C4
