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Which Throwout Bearing to Use?


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Another pre-forum, Q&A exchange with Jason Logan (forum member JayDLogan) is useful to those installing a new clutch. Jason has concerns about which type of release bearing to use. The discussion continues here at the forum::


Jason: Hello Moses!  Hope I am not bombarding you with questions?  I have sent to you a photo of two release bearings for my 1999 jeep 4.0L clutch assembly.  Both are brand new.  Which release bearing should I use? The one on the left is a composite (plastic)/steel design while the other one on the right is full cast (original design) . Thanks for any information you can give me!



Luk is at left; OEM iron casting is at right. Click on photo to enlarge. 


Moses: Both release bearings work and appear to fit the same way, right? 


I’m drawn to the cast item at right in the photo you sent.  Unless there is interference or a stack height problem, either should work.  Match-up to the OEM would be advisable…The composite looks like a possible weight savings and maybe an NVH (noise-vibration-harshness) update.


Jason: The composite/ plastic bearing came with the Luk Pro Gold clutch kit.  I was apprehensive to use this new bearing because of its construction.  I talked to Luk technical department and they said that the composite would not hang up on the bearing retainer if there was any signs of wear.  They also told me that it does not require grease at the bearing retainer friction points.


The cast release bearing is from mopar and I think I am going to install that one since it is a direct replacement from the original. I thought I would ask you to see if there was a better version of the original!  Thanks again!  


Moses:  I understand Luk’s approach, and that may be a perfectly good design—and improvement.  It’s not earthshattering either way, as each design has its merits…There is a larger concern with the TJ Wrangler clutch assembly and release bearing selection: stack height of the clutch and bearing. The master cylinder for the clutch has only so much travel, and the location of the slave cylinder determines the amount of clutch release travel.  These clutches are "self adjusting", and the release bearing and arm must be positioned correctly to allow full clutch travel and compensate for disk wear over time.  Concerns include the flywheel face (resurfacing the flywheel affects the stack height relationship to the bellhousing); the clutch disk thickness and pressure plate height; and the release bearing's yoke flanges-to-bearing face height.  The Luk and OEM bearings appear to have the same flange heights, and that would be my bigger concern...Moses

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