Defective LuK Flywheel

[g.hayduke]

I thought some might be interested in this. I was really surprised to see it.

I'm doing a clutch job on my '05 LJR and decided to replace the flywheel. I purchased a LuK Flywheel LFW484 from Summit Racing. On Saturday morning, I was ready to start putting things back together. While bolting the flywheel to the crank, I found 1 of the 6 holes to be undersized! The bolt won't fit through the hole. FUCK! I considered drilling it out but that could throw the balance off.

So I called Summit this morning and they are trying to get me a replacement expedited from LuK. The fact that we're going to Moab in a couple weeks is adding to the stress. It took about a week to get the first flywheel. When I started this, I had plenty of time to get everything done. Should still work out ok but only if I get a usable flywheel pretty quick.

I hope they don't have a big batch of bad ones.

 

[Jerry Bransford]

What makes you believe you need a replacement flywheel? RARELY is a replacement needed, at the most they usually just perhaps need a quick sanding of the surface with emery cloth or a mild grade of sandpaper to remove any possible glazing.

When I removed my flywheel at 191k miles it was still in perfect condition. Replacing the flywheel is not a normal part of a clutch job.

Unless you see physical damage to the flywheel I'd keep it and tell Summit to refund my $$$.

 

[williambmac]

was there anything wrong with your original flywheel? Usually all I do is take 120 grit on a orbital sander and dress the flywheel.

 

[Westtown Willy]

if you have Prime you can grab one a good bit quicker than another week, & if you're concerned about Summit having a bad batch that may also alleviate that issue...

 

[pagrey]

Somebody else had the same problem recently, seems like the wrong bit was put in a tool along the line somewhere.

 

[mrblaine]

I thought some might be interested in this. I was really surprised to see it.

I'm doing a clutch job on my '05 LJR and decided to replace the flywheel. I purchased a LuK Flywheel LFW484 from Summit Racing. On Saturday morning, I was ready to start putting things back together. While bolting the flywheel to the crank, I found 1 of the 6 holes to be undersized! The bolt won't fit through the hole. FUCK! I considered drilling it out but that could throw the balance off.

So I called Summit this morning and they are trying to get me a replacement expedited from LuK. The fact that we're going to Moab in a couple weeks is adding to the stress. It took about a week to get the first flywheel. When I started this, I had plenty of time to get everything done. Should still work out ok but only if I get a usable flywheel pretty quick.

I hope they don't have a big batch of bad ones.

That won't throw the balance off. The amount of material removed is miniscule and far too close to the center to affect balance.

 

[g.hayduke]

Whether or not I "need" to replace the flywheel is debatable. I'm replacing it because of the following:

• Flywheel has obvious hot spots visible after cleaning the surface with an orbital sander. So it is clearly not in "perfect condition" like Jerry's flywheel was.
• Clutch engagement was starting to become uneven and started to sort of surge shortly before the tear-down.
• Since I've owned the Jeep, the engine has had a noticeable vibration at higher RPMs (>3.5K RPM, stopped in neutral or with clutch disengaged). Replacing the clutch and flywheel should eliminate those components as possible sources of the vibration.
• If I don't replace the flywheel and the surging and/or vibration is still there, I'll be kicking myself for not replacing the GD flywheel while I had it all apart.

As for Amazon Prime, I do have it but I have found Amazon shipping to be painfully slow since early Spring. Even for in-stock items, I'm waiting up to a week or more for delivery. I have found Summit Racing shipping to be super fast for in-stock items. Shipping is expensive unless it's over a certain amount. In this case, I already made the purchase with Summit. They are getting me a new flywheel sent as soon as possible from LuK and sent me a free return label for returning the defective part.

 

[g.hayduke]

That won't throw the balance off. The amount of material removed is miniscule and far too close to the center to affect balance.

I thought that was probably the case but with my luck, I'd drill it out, reassemble it, and have a new vibration that I would always suspect was from opening up that hole.

Have you ever run into a Luk flywheel with undersized bolt holes?

 

[mrblaine]

Somebody else had the same problem recently, seems like the wrong bit was put in a tool along the line somewhere.

What's up with that? I've had several production machine jobs lately with the same issue. Two holes, 1/2" apart, one is .190, one is .185. The smaller is to press fit a pin in with .002-003 interference. The other is clearance for a 3/16" fastener. They are coming in both the same, reversed, or both wrong.

Oh, we put the wrong bit in. No, you would have to do that on purpose and mess up the CNC program to do that.
Oh, the bit broke and we didn't catch it.
No, if that happened, they would all be fucked up, they aren't.

This isn't rocket science, just basic machining. WTF?

 

[mrblaine]

I thought that was probably the case but with my luck, I'd drill it out, reassemble it, and have a new vibration that I would always suspect was from opening up that hole.

Have you ever run into a Luk flywheel with undersized bolt holes?

I promise it won't screw up the balance. No, I have not run into bad flywheels. But, if I did, it would only slow me down the amount of time it would take to drill out the hole.

You can test the theory easily. Go take a one ounce weight and stick it next to the lug nuts on your rim and go for a drive. That will show you how little effect weight has close to the centerline.

 

[pagrey]

I've had several production machine jobs lately with the same issue.

That's tough, having to check all that stuff.

I wonder if this flywheel is like that old fruitcake, it's just going to make the rounds until somebody finally eats it.

 

[mrblaine]

That's tough, having to check all that stuff.

I wonder if this flywheel is like that old fruitcake, it's just going to make the rounds until somebody finally eats it.

My packaging guy used to work 2 hours a day. 1 hour packaging, 1 hour prep for future orders. Now he is working average 4 hours a day and he is still here right now after 2pm.

We've had to go to nearly 100% inspection on parts to check for accuracy. Parts match the box number, box number is actually what we ordered, quantities, etc. It is mind numbing work that we didn't used to have to do.

 

[Artsifrtsi]

We've had to go to nearly 100% inspection on parts to check for accuracy. Parts match the box number, box number is actually what we ordered, quantities, etc. It is mind numbing work that we didn't used to have to do.

I just ordered some cube lights from Q-tec... one was correct, the second was correct on the box, but was a flush mount instead of a standard post mount.

 

[Steel City 06]

I went with the Centerforce high inertia flywheel and really like it. It makes the car super hard to stall, even with 4.10s and 35s. It also smooths out the torque when you're idling through something in gear. It is far more expensive though.

https://www.quadratec.com/p/centerforce/high-inertia-flywheel-jeep-wrangler-tj-40l
Note that the flywheel is only designed to bolt on in one orientation. Any of the other 5 positions, and the bolt holes won't line up. This is by design.

I believe all 91-04 4.0 flywheels are the same. 05-06 flywheels are different than 91-04.

 

[mrblaine]

I went with the Centerforce high inertia flywheel and really like it. It makes the car super hard to stall, even with 4.10s and 35s. It also smooths out the torque when you're idling through something in gear. It is far more expensive though.

https://www.quadratec.com/p/centerforce/high-inertia-flywheel-jeep-wrangler-tj-40l
Note that the flywheel is only designed to bolt on in one orientation. Any of the other 5 positions, and the bolt holes won't line up. This is by design.

I believe all 91-04 4.0 flywheels are the same. 05-06 flywheels are different than 91-04.

His issue wasn't the asymmetrical bolt circle, it was a bolt wouldn't go through one of the holes.

 

[briggss3]

What makes you believe you need a replacement flywheel? RARELY is a replacement needed, at the most they usually just perhaps need a quick sanding of the surface with emery cloth or a mild grade of sandpaper to remove any possible glazing.

When I removed my flywheel at 191k miles it was still in perfect condition. Replacing the flywheel is not a normal part of a clutch job.

Unless you see physical damage to the flywheel I'd keep it and tell Summit to refund my $$$.

My flywheel has what looks like surface cracks on the friction surface. Would that warrant a replacement? Maybe caused by a spring that busted.

 

[g.hayduke]

My flywheel has what looks like surface cracks on the friction surface. Would that warrant a replacement? Maybe caused by a spring that busted.

View attachment 381386

View attachment 381387

Personally, I would replace it and have mucho peace of mind.

 

[briggss3]

Is the centerforce high interia flywheel worth the additional $300 over a $70 Luk flywheel?

 

[g.hayduke]

Is the centerforce high interia flywheel worth the additional $300 over a $70 Luk flywheel?

I'm perfectly happy with an OEM-equivalent flywheel.

Maybe I don't know what I'm missing.

BTW, a heavier flywheel that helps maintain more consistent engine speed under load will also do the same when trying to accelerate. IOW, it will "help" your jeep accelerate slower, especially in the lower gears, 1st, 2nd.

 

[Mark K]

Lousy break on the mismachined flywheel, but I love my new LuK, to go with the LuK clutch. Transmission guy said my OEM flywheel (208K miles) had several suspicious spots, so we installed the LuK along with the AX15. Flywheel was less than $100 on the Am, so why not? The two have performed beautifully together for 1500 miles now.