LUK SMF new flywheel installation questions

[Mike Linger]

I bought the LUK SMF conversion kit for both my '91 and '93 trucks and installing the first one in my '93. Looking at the enclosed throwout (clutch release) bearing made by INA, it looks well made but the face of the bearing which contacts the pressure plate fingers (continuously) has a rather sharp edge going all around it. If the bearing travels beyond a certain point it would carve a groove in the clutch finger ends. A quick look at the equivalent application National and Timken release bearings shows a 3/8" larger diameter face that is also rounded on the outside edge. Question: Wouldn't I be better off in the long term buying a National of Timken equivalent? Would they work with the LUK SM?

I actually called LUK and spoke with a rep who thought any OEM release bearing "should" work with their kit. But he sounded like he wasn't really sure.

 

[jericho]

I just bought the same LUK kit . Looking at the angle of the pressure plate fingers at rest, at full compression I don't think they come close to flat, let alone beyond where I think your concern lies. I'm not worried about it, but maybe someone else here knows better.

 

[u2slow]

Is this observation before the pressure plate is installed?

Normally the fingers flatten a bit as its torqued down.

 

[ifrythings]

Here’s where the fingers sit on a luk clutch

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[Macrobb]

Remember, the surface that touches the fingers is /never/ spinning against them. The spring in the slave cylinder keeps the throwout bearing engaged(and spinning with the flywheel) at all times.

 

[aggiediesel01]

Here’s the wear the op is talking about this is more than just the rustproofing worn off, you can feel the depression in the worn area:

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Here the difference in throwout bearings, the one on the right (from LUK kit) has a pretty sharp edge that could definitely produce this kind of wear and the one on the left (National or Timken) is .400" larger in diameter and has that nice radius that we think would mostly eliminate this wear:

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[nelstomlinson]

The wear is real, but does it really matter? Is that pressure plate going to be worn out before the wear on the fingers becomes a problem?

 

[franklin2]

Like was said, the throwout bearing has pressure against the clutch fingers at all times. If it does scoot or slide on the fingers you will get a squeaking noise. These hydraulic clutches work differently than the old linkage style clutches.

 

[u2slow]

Been thinking about this one some more....

It does make sense that one of the contact faces has some curvature to account for the range of motion. On my clutches (cummins) the pressure plate fingers have curved, 'domed' tips and a flat bearing. Similar on just about any older clutch on gas engines I've relpaced. Flat fingers, as depicted above, is not what I'm used to seeing. Flat-on-flat, with the resulting wear is not ideal.

It bothers me when the aftermarket does things like this. This is supposed to be a constructively engineered solution to the problematic DMF setup. Is it carelessness? Cost savings? Is it too good a solution? One so good that its the last clutch you need buy, if it weren't for the fingers wearing off first?

I think I'd use the domed-surface release bearing for that clutch.

 

[aggiediesel01]

It bothers me when the aftermarket does things like this. This is supposed to be a constructively engineered solution to the problematic DMF setup. Is it carelessness? Cost savings? Is it too good a solution? One so good that its the last clutch you need buy, if it weren't for the fingers wearing off first?

I think I'd use the domed-surface release bearing for that clutch.

I’m not sure if it was careless but I can say that the LUK guy told us they are stuck with the bearing they supply because the Mfg (INA) is a sister company and already a preferred supplier and in their supply chain.

We’re leaning towards using the domed National bearing.

 

[Thewespaul]

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For what it’s worth, this is what comes with the 400hp south bend kits. Looks close to the National.

 

[BrianX128]

The first time you push down your clutch pedal on a luk kit versus stock you forget what any of it looked like

 

[Mike Linger]

Thanks everyone for all the input. That and the fact the LUK tech rep told me that INA bearings is a subsidiary sister company both owned by the same conglomerate, all made me decide that I'm going to run with the larger face more radius bearing. I'll let you know if I made the right decision. Eithe way I'm sure my left leg muscles will appreciate it.

 

[arizhntr]

I put a LUK in my truck 15 years ago, the t/o bearing failed 2 years ago. The failure was due to the plastic sleeve they use on these bearings. When I pulled the trans (150k miles on the clutch, lots of towing along the way) the pressure plate and the disc showed wear but both were reusable. I did replace the clutch kit and put another LUK bearing back in. If the inner collar on the bearing did not fail I would still be using the clutch for quite a few more years. I did some research and did not find a better replacement for the OEM style t/o bearing without the plastic inner sleeve. I'm not sure how many others had this issue, but I was not happy having to replace the clutch because of that failure.

 

[79jasper]

I think someone had found a all metal, greasable unit.

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