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Thread: Crank Walk Documentation

  1. #126
    When I push the clutch in the car increases rpm slightly by maybe 100rpm so I must be good for the moment I have a V160 with RPS for over 2 years without the clutch switch mod but will be doing it this weekend!

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  3. #127
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    I'm still lost as to how the clutch switch puts stress on the motor during start-up. From my understanding, the pressure plate releases the clutch off the flywheel by pressure being applied the the center of the diaphram, which puts opposing pressure at the end of the springs on the pressure plate, releasing pressure from the clutch disk and away from the flywheel. Can someone explain to me how the pressure plate puts any time of pressure on the crank?

  4. #128
    Cheifbootknocka TooJayZee's Avatar
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    Quote Originally Posted by csramotorsports View Post
    I'm still lost as to how the clutch switch puts stress on the motor during start-up. From my understanding, the pressure plate releases the clutch off the flywheel by pressure being applied the the center of the diaphram, which puts opposing pressure at the end of the springs on the pressure plate, releasing pressure from the clutch disk and away from the flywheel. Can someone explain to me how the pressure plate puts any time of pressure on the crank?
    Its not the sensor. Its the fact that you are pushing the clutch in, pushing the pressure plate, pushing the flywheel which is attached to the crank, thus pushing the crank in - which potentially would not have alot of oil on it after sitting without running for a given period of time. By bypassing the switch, allows the motor to start and get the crank lubed up before you need the clutch.

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  6. #129
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    Quote Originally Posted by TooJayZee View Post
    Its not the sensor. Its the fact that you are pushing the clutch in, pushing the pressure plate, pushing the flywheel which is attached to the crank, thus pushing the crank in - which potentially would not have alot of oil on it after sitting without running for a given period of time. By bypassing the switch, allows the motor to start and get the crank lubed up before you need the clutch.
    What? when you dis engage a clutch, it doesnt push the flywheel, and it certaintly doesn not "push the crank in".

    When you dis engage the clutch ( pedal pushed down) you are releasing pressure off the flywheel. So how is that in any way putting stress on the crankshaft?

  7. #130
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    Basically I understand the whole thrust bearing issue, as it's understandable the extra pressure from a pressure plate can cause increased wear on the thrust washer. But where I am lost is this... " why is there pressure on the flywheel with the clutch pressed in" ?

  8. #131
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    Quote Originally Posted by csramotorsports View Post
    Basically I understand the whole thrust bearing issue, as it's understandable the extra pressure from a pressure plate can cause increased wear on the thrust washer. But where I am lost is this... " why is there pressure on the flywheel with the clutch pressed in" ?
    You need to look up an exploded diagram of a clutch and see how it works, then you'll answer your own question.

  9. #132
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    Quote Originally Posted by Zach90Turbo View Post
    You need to look up an exploded diagram of a clutch and see how it works, then you'll answer your own question.
    I understand how a clutch works. The only time pressure is applied from the pressure plate to the flywheel is when the clutch is engaged, and the diaphram is pressing the clutch plate against the flywheel. The T.O.B either pushes the diaphram in the middle which pulls the outer edge towards the back of the car, releasing the clutch plate during disengangment. Or it pulls the diaphram toward the car to release the clutch plate, ie. push or pull style clutches.

    When your starting the car with out the clutch pedal pressed in, arent you starting it with the full pressure of the pressure plate pressing the clutch against the motor?

    diagrams of a clutch are here. http://auto.howstuffworks.com/clutch1.htm

  10. #133
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    Quote Originally Posted by csramotorsports View Post
    What? when you dis engage a clutch, it doesnt push the flywheel, and it certaintly doesn not "push the crank in".

    When you dis engage the clutch ( pedal pushed down) you are releasing pressure off the flywheel. So how is that in any way putting stress on the crankshaft?

    But you are putting pressure on the flywheel. For you to be able to put pressure on the diaphragm spring, there has to be resistance from somewhere. The diaphragm spring is connected to the clutch cover which bolts to the flywheel which is connected to the crank.

    Depending on which type of clutch you have, it's possible to either push or pull the crank which puts stress on the thrust surface.

    People with factory clutches don't have to worry as much, but those who have upgraded to hold 400,500,600 lb-ft will be putting even more stress on the thrust bearing.

  11. #134
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    Quote Originally Posted by verbal View Post
    But you are putting pressure on the flywheel. For you to be able to put pressure on the diaphragm spring, there has to be resistance from somewhere. The diaphragm spring is connected to the clutch cover which bolts to the flywheel which is connected to the crank.

    Depending on which type of clutch you have, it's possible to either push or pull the crank which puts stress on the thrust surface.

    People with factory clutches don't have to worry as much, but those who have upgraded to hold 400,500,600 lb-ft will be putting even more stress on the thrust bearing.


    I always figured all the resistance was eaten up by the T.O.B hydraulic assembly

  12. #135
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    Also seems that a "pull style clutch" would put the most force on the flywheel when disengaging. So I'm guessing the Supra is a pull style clutch no? And if so...has anyone converted to a push style to try and eliminate this

  13. #136
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    Crank walk is just that a myth! hundreds models of cars have clutch switches, and do you hear lots of "crank walk" complaints no, and it doesn't matter whether the clutch is push or pull type, they both put the crank under a certain amount of pressure one way or the other, but do you really suppose the engine designers and manufactures didn't consider all these aspects!

    As for all oils being crap as in,SUPRASSS waffle, well, you have had all oils properly Analise and found only one thats any good, well i suggest you find another lab.
    95 J spec 6 speed single.

  14. #137
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    Quote Originally Posted by Tricky-Ricky View Post
    Crank walk is just that a myth! hundreds models of cars have clutch switches, and do you hear lots of "crank walk" complaints no, and it doesn't matter whether the clutch is push or pull type, they both put the crank under a certain amount of pressure one way or the other, but do you really suppose the engine designers and manufactures didn't consider all these aspects!

    As for all oils being crap as in,SUPRASSS waffle, well, you have had all oils properly Analise and found only one thats any good, well i suggest you find another lab.
    ok i forgot royal purple.seriously what oil are you using?

  15. #138
    SupraForums Member spl's Avatar
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    A lot of people have reported crank walk with 2JZ-GTE so IMO it is a bit stupid to say that it's a myth... If it hasn't happened for you, it doesn't make it a myth.

    Even the push-side thrust washer in my own engine was showing significant wear when I rebuilt the engine for other reasons. It was 125 000 or so miles with the clutch switch, of which last ~20 000 with RPS Stage 2 pressure plate. Well actually I removed the switch and started to start up the car always in neutral a bit earlier but don't remember when exactly.

    The thrust washers in 2jz don't seem specially strong and I'm convinced that the 2jz thrust washer doesn't like startup (=no oil pressure) combined with thrust from a stiff pressure plate. Just remove the clutch switch and don't press the pedal when starting. Especially if you have stiffer pressure plate and/or your car has been standing for a long time...
    1994 6-speed targa with built engine, modified Holset Pro55, AEM EMS v2 and E85

  16. #139
    From the land down under Mr Ree NZ's Avatar
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    Can anyone put a ballpark figure on how many pounds of force a given clutch cover can generate safely before getting into the crankwalk danger zone?

    Im about to fit an R154 and was thinking about a full faced carbon/kevlar disc with uprated pressure plate to about 2800lb. Is that going to be too heavy to be considered safe? I will only be running about 450whp at the most so torque wont be out of control compared to most on here. Stock rev limiter too btw

    Thanks in advance

  17. #140
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    Quote Originally Posted by Mr Ree NZ View Post
    Can anyone put a ballpark figure on how many pounds of force a given clutch cover can generate safely before getting into the crankwalk danger zone?

    Im about to fit an R154 and was thinking about a full faced carbon/kevlar disc with uprated pressure plate to about 2800lb. Is that going to be too heavy to be considered safe? I will only be running about 450whp at the most so torque wont be out of control compared to most on here. Stock rev limiter too btw

    Thanks in advance
    If you don't use a twin Disc, and used a single disc with heavy PP it will happen to you my friend.

  18. #141
    From the land down under Mr Ree NZ's Avatar
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    Quote Originally Posted by quickgs View Post
    If you don't use a twin Disc, and used a single disc with heavy PP it will happen to you my friend.
    Thanks for your reply. What consitutes heavy please? And surely power levels/rev limits must have some bearing on how long before the onset of crankwalk begins, no?

    A twin clutch is out of the budget for me so I would like to install a heavy single but not so heavy that it is going to cause this too happen.. I never start my car with my foot on the clutch, I always let it warm up for 5 mins or so before driving it etc.

    Any info appreciated

  19. #142
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    Sorry just reading through this and Had Twice cents of my own and from reading most of the more relevant post gave me the conclusion that to stop/minimize crank walk your options are..

    1.Stay Stock
    2.Disable Clutch Switch
    3.Don't buy an RPS clutch kit at all anyone with any problems with crank-walk had an RPS clutch.

    At least from my reading.

  20. #143

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    Quote Originally Posted by misterjdm View Post
    Sorry just reading through this and Had Twice cents of my own and from reading most of the more relevant post gave me the conclusion that to stop/minimize crank walk your options are..

    1.Stay Stock
    2.Disable Clutch Switch
    3.Don't buy an RPS clutch kit at all anyone with any problems with crank-walk had an RPS clutch.

    At least from my reading.
    OK I want to add my 2 cents.....

    First this problem has been around for a long time on lots of makes of cars.

    The problem should really be called "crank thrust bearing wear" and this is what it was called in England in my youth. The first case I saw with my own eyes was a Mini 848 cc where the wear was so great the half thrust bearing had jumped and jammed the crank causing it to seize. This was a stock car with relatively low mileage, and incredibly low HP !!!
    These thrust bearings were half bearings not unified with the main bearing as is done now.
    I think we have all heard the DSM crank walk issues, and this was a mix of stock and modified cars.
    So yes if you run high non-stock clutch release pressures you greatly increase your risk of this type of failure.
    Disabling the clutch switch (which was not an issue on the Mini) clearly will help and I will do that on my IS300.

    I also add that the issue seems to be the design allows Oil to drain off the bearing and is not replenished quickly with a pressure feed, all the ones I have looked at are splash, but I have not looked at a 2JZ.

  21. #144
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    someone should post a DIY on the Disabling Clutch switch with pictures, because I'm still a noob and not familiar enough with where all the parts are located under the dash panel.

  22. #145
    Now...Whitesupra94
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    Quote Originally Posted by choua01 View Post
    someone should post a DIY on the Disabling Clutch switch with pictures, because I'm still a noob and not familiar enough with where all the parts are located under the dash panel.
    its the only connector directly behind the clutch pedal. push the pedal down. see where it hits. You've got your switch. Disconnect the connector and run the two wires to a switch. instead. I hid my switch as an additional theft deterrent.

  23. #146
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    I just rebuild my step mothers saturn, this is the main/thrust bearing in the center of the block. Lets get someone to make one of these for us.



    edit: the filters at work block most images sited so i couldnt see the small block bearing that looks the same. my bad
    Last edited by Smaay; 12-06-2011 at 10:43 PM.
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  24. #147

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    in usa, you have a clutch switch?

    in france, no switch, you can start in neutral position without applying clutch

  25. #148
    Looks best in drag Ki11bert's Avatar
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    Quote Originally Posted by Smaay View Post
    I just rebuild my step mothers saturn, this is the main/thrust bearing in the center of the block. Lets get someone to make one of these for us.



    edit: the filters at work block most images sited so i couldnt see the small block bearing that looks the same. my bad
    Now you're on to something. To the guy who said that crank walk was just a myth.... I'm going to tell you now that you're talking out of your ass and you have very little knowledge on the subject. The proof is in the pudding, and there is a lot of pudding to be had. Grab a spoon, bud. The unfortunate truth is that Toyota built a killer engine all around, but put little engineering and research into the thrust washer design. What makes it so terrible is that it FLOATS between the main cap and crank. Sure, the upper and lower washers "lock" together, but what good does that do when the washer wears down and is literally able to fall out of place? Now you have no thrust control and the crank is allowed to walk back and forth without restriction. Almost a tenth of an inch to be exact. The auxiliary problem is that the thrust washer only receives secondary lubrication; the kind that is a result of slung oil from the crank journals. Sure that works fine most of the time under "OEM" conditions, with pressure plates that provide only the minimum amount of holding pressure. But add a single-pressure plate with a belleville spring strong enough to push the space shuttle off the launch pad, and you're entering a world of trouble. Now you're forcing your hardened crank (or pulling depending on your clutch) against this cheap, pot metal washer with at least 5 times the force of the stock pressure plate. Complete this pudding sandwich with a nice cold morning start with a good 5 seconds of no oil pressure and active lubrication, and you just took a cool .001 off your thrust washer. Multiply that by a month of mornings and you just lost .031 off your thrust washer. (not exact measurements but you get the idea) See if you're thrust washer wants to stay put in it's comfy little spot now. Soon you'll find it in the pan like I did. A myth? Is gravity a myth? This is you're physics and measurement-backed standpoint. Plus, I don't think they make one oil that can prevent this disaster from happening. All you can do is be aware of it and plan accordingly. Here's the safe bet:

    1. BYPASS THE CLUTCH SWITCH

    2. Buy a twin or triple disc clutch. These clutches obtain the holding power by expanding the clutch surface area over multiple clutches, making it unnecessary to have a ridiculously strong pressure plate. These clutches also feature a near-stock pedal feel.

    3. Inspect the crank for walk frequently. With the engine off, have a friend slowly depress the clutch pedal while you look at the harmonic balancer. It would be best to use a dial gauge (one that checks runout) but a ruler would do the trick. You should use the ruler or dial gauge to observe the distance the harmonic balancer travels laterally. Bottom line... IT SHOULDN'T. If you get a visible amount of lateral movement, you could be in trouble. ON a GE block, the manaul states that the operating thrust range is from .0008-.0087 in. THE MAX IS .0118 in. That's tiny. Here's something for comparison: A 20AWG wire is .0320 inches. So if you can SEE your harmonic balancer move laterally, you should plan on pulling the engine soon. Hope this helps. Tricky Ricky, I hope you enjoyed your pudding.

    Note: Standard thickness for OEM thrust washers is .0764-.0783 in. I doubt these measurements differ much on the GTE block.

    Kill
    Last edited by Ki11bert; 01-06-2012 at 08:33 PM.

  26. #149

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    Quote Originally Posted by sansoub View Post
    in usa, you have a clutch switch?

    in france, no switch, you can start in neutral position without applying clutch
    Yes,
    My Brother in law from England couldn't start our manual shift cars because he didn't know to depress the clutch !!!

  27. #150

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    At the final long block tear down phase of my rebuild due to crank walk. Here's the video of Crank Run. Maybe just a tad bit out of the 1:8 thousandths of play that Toyota (11 is the service limit) recommends as the max amount of movement!

    We'll be tearing apart the block and checking out the smashed thrust washers and I'll post our finds in this thread. Also of note, with the timing belt cover removed and crank bolt off, there was extensive metal shavings from where the extreme play in the crank ground into the oil pump assembly.

    http://www.youtube.com/watch?v=AqfqM...&feature=share
    Last edited by 2jECMO; 01-15-2012 at 10:31 PM.

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