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General Clutch Medium Info & Questions...


Logical1

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Hello all! I recently replaced the clutch in the 510 (L18 with the roadster PP and Japanese disk) it worked GREAT! Not long after though my Transmission died so I replaced it. While I was in there I noticed my pilot bushing had come loose and needed to be replaced again. Replaced it, put the clutch back on and called it good. Well I guess I had some grease on my gloves and tainted the disk... Now my clutch is slipping BADLY after about 2 weeks... Frank & Jeff thought it might burn off if it wasn't badly tainted, It hasn't. So now I have to obviously get back in there and replace the disk at a bare minimum, ARRGG! Well here are some questions:

 

1. I have a bunch of good/decent disks around, but I'm feeling like I should put a brand a new disk in there because I sure as shit don't want to open the tranny up again!

 

2. My PP is only a couple months old and I did not abuse it before the tainted disk, however with the slippage could I have overheated my PP beyond usability? I know resurfacing of PP is a no-no but maybe just a emery cloth rub down and light sanding and polishing?

 

3. Is there a way to tell besides blueing/heating coloration that my PP is bad once I get it off?

 

Ok so now onto some tech geekness and theory... Please forgive the n00b questions but I bet alot of people would like to know some of these answers:

 

1. Why are pressure plates polished smooth? seems like a slightly rough hardened surface would hold alot more torque... I'm not talking crazy ridges or anything but more like the flywheel looks after resurfacing with a slight 'whirl' pattern. Is this solely to smooth clutch engagement

 

2. I have looked into aftermarket racing clutches for L motors and not many of them hold much more torque then the roadster (I think there was even a review on another site from Hainz about how the roadster clutch is close enough to racing clutches for the cost difference...) which ties into the lighter flywheel question... from what I have heard. A heavier flywheel will 'drop' harder for bigger starts, such as drag racing and machined/aluminum flywheels spin up faster for auto-x and track racing apllications yes/no?

 

3. I found a quick mention of Kevlar disks in the pressure plate torque rating thread. Anybody else use one of these bad boys?

These guys Paeco Clutches make a full clutch set for L motors and have unlimited HP rating and 6 month warranty even for drag racing! WOW! Yes its a pricey kit ($445) but for that quality and long lasting clutch I'm sold if its true...

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I have used the roadster pressure plate, and a standard clutch disk in my Datsun 521, with a L-18 that I used to pull a two horse trailer, with two horses, pretty much all over the Pacific Northwest.

Two horses, lets say 1,100 pounds each, plus the trailer, another 750 to a 1,000 pounds. Plus the truck, a small canopy, and stuff I need to show the horses at a horse show.

I find it really hard to believe you have abused your clutch more than I have.

Is your clutch throwout bearing adjust properly? There should be a little bit of movement of the throwout lever on the transmission before the throwout bearing contacts the clutch fingers. I hate to be blunt, but do you use the clutch pedal for a foot rest?

The thickness of the disk should be 8.6 to 9.0, with the disc free, or not compressed, or 7.6 to 8.0 mm installed with the pressure plate bolted up.

The Datsun pressure plate is a diaphragm spring type, this type of spring loses more tension as the disk wears out. but I could easily get 30 to 40 thousand miles of use out of a roadster pressure plate, and stock disk, using the truck like I described.

 

Your questions:

1. Flywheel surfaces and pressure plate surfaces have to be smooth to not wear out the disk rapidly.

 

2. A lighter flywheel does change RPM quicker, but the effect is most noticeable sitting in a parking lot, revving the motor in neutral. I believe with a cars that weighs approximately what it did stock, you are better off with a flywheel weight that is stock. Sure, it takes energy to rev the flywheel up, but when something tries to slow the flywheel down, you get that energy right back.

Now, if you have a lightened and gutted 510, strictly for racing, there might be an advantage in having a lightened flywheel.

 

3. As for the Paeco clutch, I again will say, I find it hard to believe you can abuse your clutch more than I have, with horse trailers, horses, and a canopy on a 521, and I have been able to get reasonable service out of a stock roadster pressure plate.

 

My old "How to modify Datsun 510, 610, 240Z engines and chassis" book lists a Torrington roller bearing. Go to a bearing supply and ask for a Torrington B1010, or a INA SC1010. This is a roller bearing that replaces the pilot bushing.

The book was published in 1973, and the bearing numbers might be out of date

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If you fried it you would likely smell it, like hot brakes. It would take a lot of contamination to make it slip.

 

When the pilot was replaced did you grease it?

 

Did you grease the splines and the cavity in the release bearing collar?

 

Check the tranny oil level. Could the front main seal have failed and it's leaking oil out the nose on the cover plate?

 

620CAFS5W71B85turbo200sx007Large.jpg

 

It would ooze out directly onto the clutch disc splines.

 

.

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Thanks for all you replies, warning early morning grumpy stream of conciseness post:

 

I'm not suggesting that I abused my clutch into slipping, I replaced it 3 months ago and it worked perfectly until I replaced my tranny and took the clutch apart to replace the pilot bushing and then replaced it with the new trans.... after that it started slipping and has gotten progressively worse... No worries on being blunt: I don't ride the clutch, ever. never have, never will. As for the kevlar clutch, just curious if anybody has some experience with these things, not saying i need one because my roadster plate slips now. just curious as for the future. I'm re-building a L20 to put in my dime eventually and if the kevlar clutches are as awesome as they claim. I would consider picking one up before I drop the built motor in like a year or so.... Thanks for the heads up on the roller bearing :) Mostly I'm just brainstorming about what I might have to replace BEFORE I pull her apart. Like the post says: academic. As for smell, I have smelled it off and on a bit but not in a 'damn I just burnt the shit of my clutch' way. I put my pilot bushing in dry, and just put a small dab of grease on the input shaft of the tranny. The front seal failing and dripping oil down the shaft sounds like a possible winner and is my #1 guess right now... The throw out bearing was the same bearing one I had just replaced 3 months prior that I got with the kit from Datsunparts.com and I left it on the collar when I swapped the tranny... not really possible to put that on backwards and put everything back together... As for the grease burning off by now, I re-packed the clutch collar with high-temp bearing grease and used the same gloves when I put the disk back <---late night dumb ass move... so the grease on there is fairly resistant to heat I'm guessing.... When I open her up I'll look for the groove on the splines :)

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Not sure if it pertains to anyone here, but here is some info for KA clutches, not sure if they interchange with the L-series. Info was compiled from posts at ka-t.org. If you want to read up more on the different setups just search whitebunny over on their site.

 

Ka24de flywheel from 240sx (225mm)

 

whitebunny setup

d21 flywheel (23lbs) (240mm)

300zx TZ series clutch from southbend (480ft lbs torque) (ko6032)....can use z31, z32 and 280z clutch as well

350z pressure plate

 

Whiter-bunny setup

RB20 flywheel (250mm)

350z clutch

350z pressure plate

 

as far as light flywheels

~15lbs is the sweet spot for the car that is daily driven

 

 

here is a link for a clutch kit. I guess nissan used the same clutch in alot of different vehichles, look at bottom of the page for applications

 

http://www.carolinaclutch.com/ShowItem/105447.aspx

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Define slipping. Is there noticeable RPM increase with lack of acceleration under heavy load?

 

Also the Roadster pp is a monster. Even with a bit of grease on it, once locked up it's hard to believe the lowly L18 could torque it's grip loose! (no offense intended here) :lol:

 

 

 

Check tranny oil level.. if low it had to have gone somewhere. I assume that when changing the clutch you emptied it to remove and re-filled it. Are there oil drips anywhere on the bell area of the tranny. Sometimes hard to locate as wind blows it back and off. Rear engine seals can leak but takes a lot of oil to work it's way around to the clutch side of a spinning flywheel. This is a remote possibility because you did change to a different tranny.

 

 

 

Is it possible that the clutch is not being fully engaged?? Like driving around with your foot half down on the pedal. Drives and shifts just fine until you put a heavy load on it and it slips. Possible causes:

 

Damaged clutch arm on new tranny.

 

Release bearing or collar catching on input shaft cover plate.

 

Foreign object caught in PP, like nut or bolt.

 

Different slave or slave push rod. Not allowing full travel of clutch arm to rest position. Slave seized and not returning to rest position. Easy to check... OR

 

Master not adjusted/releasing fully and there is still pressure in the line to the slave cylinder. Easy to check.

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The slippage continued to worsen... a couple days ago, I started hearing a steel on steel whine from the transmission clutch area. Immediately parked the car and didn't driver her till I could move it into my new shop. Limped her down to the shop and pulled the tranny out (damn it went fast! I think I could do it in my sleep now) and um well this is what I found....

Car373.jpg

Car374.jpg

Car375.jpg

 

The Throw out bearing was totally seized... The friction disk looked ok on the friction area but the steel center where the springs are was blue & purple from heat... Flywheel looked ok though :) I'm guessing that the slippage heated the the whole assembly up and seized the throw out bearing and then that obviously cause the rest of the damage... Slippage Still a mystery though, No oil leaks of any kind. front seal was clean and dry & no oil from the engine. There goes $250.00 :angry:

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There must be clearance between the throwout bearing and the fingers of the clutch pressure plate. These two parts cannot touch, unless you are actually depressing the clutch. When you put it back together again, make sure you can wiggle the arm that the slave cylinder, before it touches the pressure plate fingers.

The throwout bearing is not designed for continuous duty, the only time it should have a load on it at any RPM faster than an idle is when you shift, and that should be less than a second or two.

 

For some reason your throwout bearing was continuously pushing on the pressure plate. This made your clutch slip, and greatly increased the wear on the disk. It also wore out the throwout bearing. As the disk wore, the fingers on the pressure plate moved even closet to the throwout bearing, increasing the force on the bearing, and making the clutch slip even more. Until something finally gave up.

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There must be clearance between the throwout bearing and the fingers of the clutch pressure plate. These two parts cannot touch, unless you are actually depressing the clutch. When you put it back together again, make sure you can wiggle the arm that the slave cylinder, before it touches the pressure plate fingers.

The throwout bearing is not designed for continuous duty, the only time it should have a load on it at any RPM faster than an idle is when you shift, and that should be less than a second or two.

 

For some reason your throwout bearing was continuously pushing on the pressure plate. This made your clutch slip, and greatly increased the wear on the disk. It also wore out the throwout bearing. As the disk wore, the fingers on the pressure plate moved even closet to the throwout bearing, increasing the force on the bearing, and making the clutch slip even more. Until something finally gave up.

 

So I'm curious here, your saying if you get under your car and reach up onto the clutch fork you can move it away from you slave cylinder? I don't think there is any part of the throw out mechanism that retracts the throw out bearing/sleeve only the force of the PP fingers when you let off the clutch pedal. Yes/no?

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The release bearing comes dry, you packed with grease before installing?

 

The 200mm uses the largest bearing collar so a wrong collar would be smaller and not hold the bearing against the fingers.

 

 

Yep, I packed it when I first got it (for the clutch swap) and re-packed it when I did the tanny swap. The clutch worked great for several months until I just did my tranny swap in which the ONLY thing I changed was the pilot bushing and tranny. The PP had no visible damage when I swapped the tranny and left the throw out bearing on the same clutch collar... After packing the bearing I wiped it down so it wasn't globbed up with grease it but it was well lubed as was the inner channels of the throw out bearing collar.

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Yep, I packed it when I first got it (for the clutch swap) and re-packed it when I did the tanny swap. The clutch worked great for several months until I just did my tranny swap in which the ONLY thing I changed was the pilot bushing and tranny. The PP had no visible damage when I swapped the tranny and left the throw out bearing on the same clutch collar... After packing the bearing I wiped it down so it wasn't globbed up with grease it but it was well lubed as was the inner channels of the throw out bearing collar.

 

Had to ask, sometimes it's the simple things. :D

 

So what tranny was in the car and what tranny did you swap in?? As the problem occurred after the change.

 

Did you use your old slave cylinder?

 

Did you use your old clutch arm?

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  • 3 weeks later...

So does the stock 510. There is an adjustment for free play also.

 

Well I have never had my spring, nor seen one... Any pics? I bolted up my tranny for test fitting last night and found the problem! When I tightened up the bolts on the tranny to the motor and my clutch fork was WAY to close to the slave cylinder, I couldn't even bolt the slave up with the rod pushed all the way in (just re-built Master & slave) so I know they are working. So Obviously the clutch was partially engaged and causing slippage. So I'm guessing this is a throw out collar mismatch or clutch fork? I'll re-cap what I did changed just to freshen up:

 

1. dogleg on a L18 - changed out the clutch to a roadster. worked great Changed: pressure plate, friction disk, Throw out bearing - nothing else!

2. Tranny went bad - Swapped it out for another dogleg (maybe different year) Only changed the tranny (re-used all previous clutch parts). Tranny bolted right up and fit/ran great but now the clutch was slipping and died...

3. Pulled out everything!

4. Test fit tranny with new clutch installed and with everything properly in place, The clutch fork is to far forward for slave cylinder installation.

 

I have the 38.5mm collar from my first dogleg. Did the different year doglegs require different collars? I searched around and found the clutch collar size chart:

clutch.replacement.figures.jpg

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  • 2 weeks later...

Well I have never had my spring, nor seen one... Any pics? I bolted up my tranny for test fitting last night and found the problem! When I tightened up the bolts on the tranny to the motor and my clutch fork was WAY to close to the slave cylinder, I couldn't even bolt the slave up with the rod pushed all the way in (just re-built Master & slave) so I know they are working. So Obviously the clutch was partially engaged and causing slippage. So I'm guessing this is a throw out collar mismatch or clutch fork? I'll re-cap what I did changed just to freshen up:

 

1. dogleg on a L18 - changed out the clutch to a roadster. worked great Changed: pressure plate, friction disk, Throw out bearing - nothing else!

2. Tranny went bad - Swapped it out for another dogleg (maybe different year) Only changed the tranny (re-used all previous clutch parts). Tranny bolted right up and fit/ran great but now the clutch was slipping and died...

3. Pulled out everything!

4. Test fit tranny with new clutch installed and with everything properly in place, The clutch fork is to far forward for slave cylinder installation.

 

I have the 38.5mm collar from my first dogleg. Did the different year doglegs require different collars? I searched around and found the clutch collar size chart:

clutch.replacement.figures.jpg

 

Dude adjust your master cylinder at the fire wall, what you have is a "preloaded clutch", and nobody tell me hydro systems dont have adjustment ...worked for a performance clutch company for over 5 years ASE mechanics always thought that too...old wives tail. Also replace PP broken diaphram fingers=bad clutch replace!

Also stay away from Kevlar=crap the resins in Kevlar boil out as its heated and make it slip worse. They are known for having the worst coeffeicient of friction look for a good organic disk with copper fibers in it, copper reduces heat faster than just a normal organic disk most high end performance cars come from the factory with copper impregnated organic disks and this is why, also stay away frome Puck discs for street use they are an on-off switch that greatly wears your PP and flywheel surfaces. Blue spots and heat cracks are NO indication of a bad PP, warping is your enemy anything over .040in is no good. Put a straight edge across the facing on the PP you will notice the inside edge will be bowed in if the gap is over or at .040in toss it. dont sand your pressure plate either does nothing.

Last the clutch fork could be bent compare with another to be sure. Um you didnt put a longer slave rod in it did you? this will throw of your leverage ratio put the old one back in and adjust properly.

521Dave

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