Yellow Rose
Suspended
- Joined
- 22 November 2001
- Messages
- 2,256
My transmission is making noises that I am not sure if it is the throwout bearing, mainshaft bearing or countershaft bearing. I say this because the sounds are different under respective conditions. Here goes.
Start engine first thing in the morning, with transmission in neutral, clutch out I hear what may be the throwout bearing. Transmission still in neutral, I push in the clutch and the noise goes away. Vehicle is not rolling. Noise seems to be quieter as things come up to operating temperature. Throwout bearing?
Start from a dead stop and as I am going through the gears applying gas - not stomping on it, just normal driving - I hear a "mechanical whirl" or "mechanical growl" that becomes quieter in each gear. In 4th gear, the noise is quiet enough so as to be almost masked by road / wind noise. In 5th gear, I cannot hear the noise at all, but I am not sure if there is no problem with 5th gear or if like the previous gears the noise is present but inaudible to my ears. Input shaft bearing?
Steady-state cruising in any forward gear, let off the gas and with the clutch still engaged, I hear the same noise but a slightly different pitch and not as loud. Again, loudest in 1st gear and quieter in 4th gear. Countershaft bearing?
Driving in 4th gear, clutch in, downshift to 3rd gear, but do not let out on the clutch and there is a different noise as if the mainshaft RPM is increased. Clutch still in but move the gear selector shaft to neutral and the noise is gone. Clutch in, downshift to 2nd gear, but do not let out on the clutch and there is this same noise but louder as if the mainshaft RPM is increased even more to simulate shaft speed it would be spinning at so as to maintain the same vehicle speed. Do this again for 1st gear and this noise is even louder. Input shaft bearing?
I have no difficulty shifting up or down into any gears, so I think that rules out the synchros and clutch. I have always used Redline fluid.
Here is a good comparison. If you have watched the in-car video of the machines in the JGTC series, you can hear a very distinct mechanical noise of the Hewland transmission. My noises are similar. I think Hewlands have straight cut gear to transmit power optimumly, at the compromise of quietness. The NSX transmission gears are cut at an angle to run quieter.
Any ideas?
Start engine first thing in the morning, with transmission in neutral, clutch out I hear what may be the throwout bearing. Transmission still in neutral, I push in the clutch and the noise goes away. Vehicle is not rolling. Noise seems to be quieter as things come up to operating temperature. Throwout bearing?
Start from a dead stop and as I am going through the gears applying gas - not stomping on it, just normal driving - I hear a "mechanical whirl" or "mechanical growl" that becomes quieter in each gear. In 4th gear, the noise is quiet enough so as to be almost masked by road / wind noise. In 5th gear, I cannot hear the noise at all, but I am not sure if there is no problem with 5th gear or if like the previous gears the noise is present but inaudible to my ears. Input shaft bearing?
Steady-state cruising in any forward gear, let off the gas and with the clutch still engaged, I hear the same noise but a slightly different pitch and not as loud. Again, loudest in 1st gear and quieter in 4th gear. Countershaft bearing?
Driving in 4th gear, clutch in, downshift to 3rd gear, but do not let out on the clutch and there is a different noise as if the mainshaft RPM is increased. Clutch still in but move the gear selector shaft to neutral and the noise is gone. Clutch in, downshift to 2nd gear, but do not let out on the clutch and there is this same noise but louder as if the mainshaft RPM is increased even more to simulate shaft speed it would be spinning at so as to maintain the same vehicle speed. Do this again for 1st gear and this noise is even louder. Input shaft bearing?
I have no difficulty shifting up or down into any gears, so I think that rules out the synchros and clutch. I have always used Redline fluid.
Here is a good comparison. If you have watched the in-car video of the machines in the JGTC series, you can hear a very distinct mechanical noise of the Hewland transmission. My noises are similar. I think Hewlands have straight cut gear to transmit power optimumly, at the compromise of quietness. The NSX transmission gears are cut at an angle to run quieter.
Any ideas?
. So I would suspect one of the three countershaft bearings, but hard to say which from the driver's seat.
HP is like crack.....addictive but legal. 
