Questions about choosing the right clutch kit from Marlin Crawler

[harry newton]

1. What's the practical difference between a 900 & 1200 foot pound pressure plate? (yes, I know, 300 foot pounds).
2. Do you bother replacing non torque to yield pressure plate bolts?
3. Do you change the teeth spacing in your flywheel?

I called Marlin Crawler ([phone]) today who does not offer an OEM spec 900 foot pound pressure plate in any of their 5-piece clutch kits.

The only kit they have to fit my vehicle is the MCCL-128 for $300

• Aisin 1200 pound pressure plate

• Seico clutch with steel springs

• Nachi pilot bearing

• Nachi throwout bearing

• Plastic spline alignment tool

They recommend pressure plate bolts even though they mentioned they're not "torque to yield", whatever that means to me in practice:

• MCHT-411

They also sell a flywheel where you can specify the teeth spacing, again, whatever that means to me in practice:

• MCCL-221A

1. What's the practical difference between a 900/1200 pound pressure plate?

1. Do you bother replacing non torque-to-yield pressure plate bolts?
2. Do you change the teeth spacing in your flywheel? Why?

[RonNNN]

My thoughts are the more foot pounds would do two things, make the clutch harder to push, but at the same time make the clutch slip less likely. Many clutch bolts are designed to stretch when tightened and should not be reused. Teeth on the flywheel do not change, they are only for starter motor to flywheel function.

[Xeno]

They may be of a higher grade than the originals. After all, the pressure on them would be higher with the stronger pressure plate.

Different applications, different starters. It would be something you would want to check to make sure you get the correct tooth spacing for your application.

300 pound extra clamping pressure on the clutch plate. Ergo, reduced likelihood of slippage under extreme conditions.

Normally no but when installing heavier duty components I would highly recommend it.

No because it will no longer match your starter pinion. Measure and purchase the correct spacing for your own application.

[harry newton]

He who is Xeno said on Tue, 14 Nov 2017 15:35:55 +1100:

There must be a tradeoff, simply because there always is a tradeoff.

I get the 1/3 greater clamping, so, in *extreme* loads, like towing a trailer up the Sierra Nevada mountain range, the 1200 pound should slip less.

What happens under normal loads? Nothing different?

[harry newton]

He who is RonNNN said on Mon, 13 Nov 2017 22:07:30 -0600:

I can't possibly disagree as it's a huge 1/3 more torque, but Marlin Crawler said it's about the same pedal force. Makes no sense, right?

Then I asked what's the difference and they say the obvious, which really doesn't tell me much practically, which is that the clutch plate is against the flywheel with 1/3 more force.

What I don't get is what that means, practically, to me?

I guess if I habitually tow a trailer up the Sierra Nevada mountain range that I'd want "more force" against the flywheel ... but what does it mean for "normal driving".

What's the tradeoff?

I think I'll get the bolt kit and I won't change the flywheel teeth. I can't imagine why they even offer that.

[Xeno]

Higher *initial* pedal pressure required is about all I can think of. It's a diaphragm type pressure plate so the highest pedal force required is at the beginning of pedal travel but this reduces once the diaphragm gets towards overcentering. This makes it much easier to *hold* the clutch pedal in the disengaged position. Bit of info here;

In that way it is vastly different from the coil spring type pressure plate where pedal pressure starts out high - and gets higher the further the pedal is depressed.

Exactly. It should give a firmer takeup however.

[Xeno]

It's the way diaphragm plate clutches work.

[Clare Snyder]

1200 lb clutch will build your left thigh muscle in traffic and will grip a little tighter. Basically a truck or race modification> (Once I'm movong I generally don't use the clutch)

Torque to yeild bolts are "stretched" when tightened and must be replaced. I don't think I've ever replaced clutch bolts - would on a drag car, but they use automatics almost exclusively today

[Scott Dorsey]

A stiffer feeling clutch. Probably no difference in life.

I would do it. I'd replace the throwout bearing and anything else in the bell end that looks the slightest bit worn. Better to change it now while you have it apart than have to change it later when it's not. My inclination is also to clean everything out with naptha and to repack the new bearing with mobil 1 grease.

You would do that if you wanted to use a different starter. Maybe the starter for your model is discontinued. Maybe you have a box of cheap starters with slightly different teeth. I have had to do it before when I could not get a starter with the correct bendix.

--scott

[harry newton]

He who is Clare Snyder said on Tue, 14 Nov 2017 09:23:25 -0500:

I'm gonna get the bolts but I don't think I need them, as you explained. I'll get them because (a) they're only 7 bucks, and (b) Toyota says to use new bolts every time.

But I agree that I can re-use the old bolts too, so I'll forget about this for now as *choosing my first clutch kit* is the more important goal.

I've been researching this on the side and I'm still confused, but one thing I learned is that the torque from an engine is only about 300 foot pounds or less (278 foot pounds according to this quick search):

So what I don't get at all, is if an engine only generates 300 foot pounds of torque, why would we even need a 900 foot pound pressure plate, given that the ratio of the flywheel diameter to clutch plate diameter is fixed at what? Almost 1 to 1? Or is it 2:1 or 3:1?

How does this math work that a 1200 foot pound clutch does ANYTHING useful?

[harry newton]

He who is Scott Dorsey said on 14 Nov 2017 10:14:44 -0500:

I hate when I don't understand simple things.

I just called Marlin Crawler at [phone] and spoke to Brendan, who, shockingly, couldn't answer my question of what difference a 900 pound stock pressure plate would make with respect to a 1200 pound clutch pressure plate in actual driving.

Since an engine only develops around 300 foot pounds of torque, the flywheel to clutch friction surface area has to take those 300 foot pounds, so I asked him if he could measure the flywheel and clutch but he said he couldn't (which is fair enough) since the web site doesn't say what the diameters are.

When I asked Brendan why they even sell a 1200 pounder, he mentioned that they have bigger tires than stock, which is fine - but Brendan couldn't explain why that matters.

So, I really don't understand what 1200 pounds does for ANYONE. Clearly my application doesn't need it (which all of you said).

But, what does 900-to-1200 pounds do for ANY application when the engine can't develop more than 300 foot pounds of torque in the first place?

[Phil Kangas]

The 300 foot pounds of torque is the rotational power of the engine. The 1200 pounds of the pressure plate is the clamping pressure, not rotational power. This increase in clamping pressure raises the friction slip point. They are not related.

[Scott Dorsey]

It not only raises the friction slip point, but narrows it as well. So if you're racing and your goal is to pop the clutch as quickly as possible, and you have the pedal depressed just barely past the friction point, the stiffer clutch will make for a faster break off the line without riding it at idle.

--scott

[Phil Kangas]

+1 :>)

[harry newton]

He who is Phil Kangas said on Wed, 15 Nov 2017 10:15:24 -0500:

Can someone summarize, for me, what a 900 foot pound OEM pressure plate versus a 1200 foot pound pressure plate means, in real terms, for a 2WD road vehicle that is not used for towing or for racing?

[hubops]

At this point - I suspect not.

[Terry Coombs]

  It means that your clutch will be slightly harder to push and hold .   --   Snag

[Scott Dorsey]

A less sore leg.

--scott

[harry newton]

He who is Terry Coombs said on Wed, 15 Nov 2017 11:18:18 -0600:

If that's all it means, in practical terms, then why do they sell it? Is it just marketing (like high-octane fuel)?

Even high-octane fuel has a benefit for the cars that need it. What's the expected benefit of a 1200 pound clutch over a 900 pound one?

That's all that Marlin Crawler sells, for example.

[Scott Dorsey]

Because a lot of people want to go fast, and half a second faster off the line can mean the difference between first place and no prize at all.

It has a huge benefit because running 100LL lets you build engines with way higher compression ratios than running street gasoline will. The difference in horsepower is substantial.

As I said in a previous post, being faster off the line.

You want to race, you buy racing products. You want to tool around on the streets, don't buy racing products.

--scott