Howdy, Long time gleaner of advice from the forum. First time post!
Just finished a clutch job on my 1998 TJ Sport 4.0 (just turned 170,000mi). Noticed lots of posts concerning transmission/clutch issues, whining, clicking sounds with clutch pedal completely released (foot off). Many responders noted that the noise couldn't be the throw-out bearing, because the bearing should only contact the clutch pressure plate spring when the pedal is depressed. Suggestions included bad pilot bearing, bad transmission shaft input bearing, etc. What I discovered while performing the clutch job may not have been realized by many shick shift TJ'ers (and late model YJ's as well as JK's, I believe), but here goes: THE WAY THE CLUTCH MECHANISM IS DESIGNED CAUSES THE THROW-OUT BEARING TO BE IN CONSTANT CONTACT WITH THE PRESSURE PLATE SPRING, AND THEREFORE THE THROW-OUT BEARING IS SPINNING ALL THE TIME NO MATTER WHAT YOU DO!!!.
The "double wishbone" style clutch fork on these transmissions has no return spring to pull the throwout bearing back into a "resting" position (there are retainer springs for the throwout bearing as well as a retainer spring for the opposite ball joint from the slave cylinder, but these do not provide any return force), and the hydraulic slave cylinder has an internal "constant pressure" spring, which constantly attempts to push the clutch fork forward toward the pressure plate and take-up any gap between the throw-out bearing and the pressure plate spring. The only thing that stops this forward movement is contact between the throw-out bearing and the pressure plate spring. Therefore the throw-out bearing is ALWAYS making contact with the clutch and the TB is ALWAYS spinning. The pressure alone from the slave cylinder spring is not enough to release the clutch, but it is certainly enough to cause constant contact between the pressure plate spring and TB.
After all this long detail of the issue, my points are the following:
#1: Make sure you purchase a high-quality throw-out bearing during clutch replacement as it will be spinning ANYTIME THE ENGINE IS RUNNING. . I got one of those crap Chinese plastic TB's in my Autozone kit. Went to Oreilly's and their kit had the same junk bearing. Bought a separate NATIONAL brand cast iron/steel TB for my application.
#2 Don't immediately rule-out a bad TB as the cause of transmission noise just because your foot is off the clutch!
Enclosed are some pics of the clutch release slave (had to use full force of my index finger to get the slave spring to compress - this is the amount of force that is pushing the throw-out bearing into constant contact with the pressure plate spring. Also enclosed are pics of the cheap plastic TB in the local auto supplier's clutch kits; you're asking for trouble if you install one of these!
Just finished a clutch job on my 1998 TJ Sport 4.0 (just turned 170,000mi). Noticed lots of posts concerning transmission/clutch issues, whining, clicking sounds with clutch pedal completely released (foot off). Many responders noted that the noise couldn't be the throw-out bearing, because the bearing should only contact the clutch pressure plate spring when the pedal is depressed. Suggestions included bad pilot bearing, bad transmission shaft input bearing, etc. What I discovered while performing the clutch job may not have been realized by many shick shift TJ'ers (and late model YJ's as well as JK's, I believe), but here goes: THE WAY THE CLUTCH MECHANISM IS DESIGNED CAUSES THE THROW-OUT BEARING TO BE IN CONSTANT CONTACT WITH THE PRESSURE PLATE SPRING, AND THEREFORE THE THROW-OUT BEARING IS SPINNING ALL THE TIME NO MATTER WHAT YOU DO!!!.
The "double wishbone" style clutch fork on these transmissions has no return spring to pull the throwout bearing back into a "resting" position (there are retainer springs for the throwout bearing as well as a retainer spring for the opposite ball joint from the slave cylinder, but these do not provide any return force), and the hydraulic slave cylinder has an internal "constant pressure" spring, which constantly attempts to push the clutch fork forward toward the pressure plate and take-up any gap between the throw-out bearing and the pressure plate spring. The only thing that stops this forward movement is contact between the throw-out bearing and the pressure plate spring. Therefore the throw-out bearing is ALWAYS making contact with the clutch and the TB is ALWAYS spinning. The pressure alone from the slave cylinder spring is not enough to release the clutch, but it is certainly enough to cause constant contact between the pressure plate spring and TB.
After all this long detail of the issue, my points are the following:
#1: Make sure you purchase a high-quality throw-out bearing during clutch replacement as it will be spinning ANYTIME THE ENGINE IS RUNNING. . I got one of those crap Chinese plastic TB's in my Autozone kit. Went to Oreilly's and their kit had the same junk bearing. Bought a separate NATIONAL brand cast iron/steel TB for my application.
#2 Don't immediately rule-out a bad TB as the cause of transmission noise just because your foot is off the clutch!
Enclosed are some pics of the clutch release slave (had to use full force of my index finger to get the slave spring to compress - this is the amount of force that is pushing the throw-out bearing into constant contact with the pressure plate spring. Also enclosed are pics of the cheap plastic TB in the local auto supplier's clutch kits; you're asking for trouble if you install one of these!
Stick shifters read this - throwout bearing issues
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