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Registered
Join Date: Jun 2008
Location: Paris, France
Posts: 101
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G64 Transmission grinding noise
Hello Guys,
i unfortunately have another problem with a 993 Twin Turbo. It has the G64.51 transmission and of course AWD. The problem is that the transmission makes a grinding noise at low rpm only, after shifting the speeds, and disappear when the car is launched at higher speed. The noise is only related to the transmission as is occurs only when a speed is engaged at low rpm. The noise and vibrations from the transmission are transmitted to the central tube with the shift mechanism and the front differential. It misleaded me first as the sound seemed to come from the front of the vehicle and not the rear. We only noticed that the sound actually comes from the trany when we lifted the car with the wheels spinning. We tried to swap the central tube and differential with another, flushed the transmission, but the problem remains. Few items remain on the suspect list, like the planetary gearset in the rear limited speed differential, the viscous clutch, or transmission bearings. I didn't find any related Technical information bulletin. I'd like to know if this is a well know problem and if any of you had a similar experience with a 993 AWD; any suggestion is welcome Thanks! |
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06-19-2010, 12:38 PM
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Registered
Join Date: Oct 2003
Location: London Ont Canada
Posts: 3,120
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There is a chance a previous owner has installed the single mass flywheel. They are known to make noise in low gear /rpm situations.
__________________
1980 911 SC 3.6 coupe sold 1995 993 coupe 1966 Mustang Shelby clone 1964 Corvair Spyder Turbo gone 2012 Boss 302 |
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06-20-2010, 09:26 AM
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Join Date: Dec 2010
Posts: 8
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Same problem
Did you ever find the culprit? I have the same problem in an 89 C4. Just low revs. I also hear a clunk when changing gears....although not all of the time.
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01-19-2011, 01:02 PM
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Join Date: Oct 2010
Posts: 63
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Quote:
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02-03-2011, 03:59 PM
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Registered
Join Date: Jun 2008
Location: Paris, France
Posts: 101
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it's funny you're mentioning the central differential, because i was today talking about it.
the only problem is that we found out that the grinding noise seems to be audible only in first gear. When starting in 2nd gear, it seems to be quiet. As soon as i release the first gear, noise stops. the noise comes from the gearbox for sure as we listened the transmission running with the car on a lifter. by the time, i teared apart the transmission, replaced few worn parts like selector forks, synchro rings, the first and second gear wheels, but not the wheels on the fixed shaft which seemed to be fine. Gear wheels seemed fine, but the synchro teeth were worn. when i put back the transmission in the car, i had the same noise; exactly, again. so now, i only think about the fixed gear wheel of first gear that might be slightly bent, but impossible to see, or some central differential problems. what do you think? |
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02-03-2011, 05:44 PM
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