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1j crank walk

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Old 06-03-12, 02:10 PM   #16
xspsi6
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Originally Posted by scoobySC3 View Post
The way my feeble brain understand it is that when the engine is running you have oil pressure, which the main and rod bearings "float" on, but with the engine off, you have no oil pressure, so the bearings are in direct contact with the crank as they do not have the oil as a buffer. So when you push in the clutch with the engine off you are moving the crank, and putting more stress on the bearings, then you turn the key/start the engine with the clutch depressed and you get a moment of no oil pressure and the engine internals rotating with all of that stress from the crank not being in good alignment, so it would put extra wear on all of the bearings. Now with the car running and the clutch depressed, you have that oil pressure/buffer so it should not put as much stress on the bearings, but probably still not ideal to have the crank move forward/aft at all.

Does that sounds right lol?
Thanks,
Rick
Yes this is correct as the lack of hydrodynamic lubrication upon dry start up along with a stiffer than stock clutch pressure plate to add clamping force to a clutch set will cause a major thrust bearing failure since there is metal to metal contact during the first couple of seconds of run time .

Here is a good read on how hydrodynamic lubrication works...
http://www.marinediesels.info/2_stro...ubrication.htm
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Old 06-03-12, 02:41 PM   #17
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I have never heard of this happening to any other motor besides the 2jzgte. Like stated before the supra community lowered the chances of this happening by doing the clutch bypass mod. Hope you get your problem sorted out and come back stronger. Good luck
This is a huge issue on the 4g63t as stated already in this thread. Especially 7 bolts. At any rate, it can happen to ANY engine with a heavy clutch, and more quickly depending on things like clutch start switches, holding the clutch in at traffic lights, and high rpm shifts. It can also happen in automatic cars if the converter ballons.

All you can do is disable the clutch switch, and try to avoid the situations mentioned above that will accelerate thrust wear.
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Old 06-03-12, 06:54 PM   #18
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Originally Posted by scoobySC3 View Post
The way my feeble brain understand it is that when the engine is running you have oil pressure, which the main and rod bearings "float" on, but with the engine off, you have no oil pressure, so the bearings are in direct contact with the crank as they do not have the oil as a buffer. So when you push in the clutch with the engine off you are moving the crank, and putting more stress on the bearings, then you turn the key/start the engine with the clutch depressed and you get a moment of no oil pressure and the engine internals rotating with all of that stress from the crank not being in good alignment, so it would put extra wear on all of the bearings. Now with the car running and the clutch depressed, you have that oil pressure/buffer so it should not put as much stress on the bearings, but probably still not ideal to have the crank move forward/aft at all.

Does that sounds right lol?
Thanks,
Rick
This is the first time I have heard of crankwalk and what you described makes a lot of sense.
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Old 06-04-12, 09:45 AM   #19
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Crankwalk is real and what others have said above is correct.
lack of oil pressure can do crazy things to your engine.
Inline engines have it even worse because the crank is so long and it needs to be perfectly aligned.
I disabled my clutch start switch years ago.

abbreviated DIY:
find clutch pedal (if someone asks for a picture for this step just leave right now).
at the top against the firewall side there is a switch which gets pressed in when the clutch pedal is all the way at the bottom.
Remove said connector on said switch, and insert a small wire or paperclip to jump the 2 pins.

This will get your car to start now without the clutch being depressed. It will not affect cruise control or anything else because that is all take care of by the other clutch switch which engages when the pedal is only slightly pressed (there are 2 sensors on the clutch).
Also, If you are using an auto ecu on a manual harness (not so common scenario), this is how you get the starter to work.
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Old 06-04-12, 09:22 PM   #20
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Originally Posted by stockhatch View Post
This is a huge issue on the 4g63t as stated already in this thread. Especially 7 bolts. At any rate, it can happen to ANY engine with a heavy clutch, and more quickly depending on things like clutch start switches, holding the clutch in at traffic lights, and high rpm shifts. It can also happen in automatic cars if the converter ballons.

All you can do is disable the clutch switch, and try to avoid the situations mentioned above that will accelerate thrust wear.
You learn something new everyday. I have owned all kinds of cars but no Mitsubishi. I haven't seen any auto supra have crankwalk. The only supra's I did see having that problem were the ones with unsprung disks. The 2jzgte that were having that problem were assembled in Mexico from what I can remember. It's been a while since I've been out off the supra community and I'm getting old so my memory isn't all that great
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Old 06-05-12, 08:44 AM   #21
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WAIT WAIT WAIT!!! okay i understand how this works. but if your tranny is in neutral. why is the crank being pushed when you press the clutch in??

ive driving sticks most of my life. now correct me if iam wrong. but if iam in neutral right. iam disengaged from the engine correct?? then if i shift into gear then iam making contact with the crankshaft right??
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Old 06-05-12, 09:34 AM   #22
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WAIT WAIT WAIT!!! okay i understand how this works. but if your tranny is in neutral. why is the crank being pushed when you press the clutch in??
ive driving sticks most of my life. now correct me if iam wrong. but if iam in neutral right. iam disengaged from the engine correct?? then if i shift into gear then iam making contact with the crankshaft right??
No your disengaged from the tranny in neutral the pressure plate is always attached to the flywheel
and the flywheel to the crank. When you step on the clutch in a 6spd or 154 the slave cylinder pulls the Pressure plate off the disk and flywheel but it does put pressure on the front thrust bearing and over time or extreme PP torque ratings will cause play in the thrust bearings and may and I have seen on several occasions the rear thrust bearing just fall into the oil pan on both V160's as well as 154's this is the reason for the clutch delete as well as most high hp supra guys going to multiple plate clutches for less extreme pressure from the plate and the ability of the 2,3,4, disc configurations to handle the HP
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Old 06-05-12, 09:50 AM   #23
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Originally Posted by SEXC View Post
You learn something new everyday. I have owned all kinds of cars but no Mitsubishi. I haven't seen any auto supra have crankwalk. The only supra's I did see having that problem were the ones with unsprung disks. The 2jzgte that were having that problem were assembled in Mexico from what I can remember. It's been a while since I've been out off the supra community and I'm getting old so my memory isn't all that great
So my RHD 95 Supra Direct import from Japan had a 2jzgte from MexicoLMAO and thats why when I disassembled to build my 2JZ after it being in the car for 17yrs with a RPS max clutch About 3yrs on clutch and the factory sprung flywheel I was starting to get some very remedial crank walk as evident on the front bearing being outside of factory spec and some very light wear noted on the bearing.
Also unsprung disks have no bearing on crank walk, its the Pressure plate that creates the issue and lack of oil on dry start up between the thrust bearing and crank that wears away the bearing face and eventually goes outside of tolerance!!!!!!!!!!!
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Old 06-05-12, 10:52 AM   #24
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so if you have gotten a engine off a jdm auto. more than likely the bearings are in better shape due to no clutch wear?? interesting..
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Old 06-05-12, 10:58 AM   #25
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so if you have gotten a engine off a jdm auto. more than likely the bearings are in better shape due to no clutch wear?? interesting..
Theoretically yes but the point is the clutch start delete is a huge part of the equation. It also doesn't take alot of time or energy to to pull the pan on a JDM motor before installing and check the thrust bearings and tolerance, its only 1 Cap.
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Old 06-05-12, 11:25 AM   #26
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where at??

Click the image to open in full size.
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Old 06-05-12, 12:13 PM   #27
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Its main cap #4 this cap is larger than the rest and has a detent in the cap for the thrust bearing on each side of the cap there a 4 total 2 on the cap and 2 on the block casting for cap.
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Old 06-05-12, 12:19 PM   #28
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No your disengaged from the tranny in neutral the pressure plate is always attached to the flywheel
and the flywheel to the crank. When you step on the clutch in a 6spd or 154 the slave cylinder pulls the Pressure plate off the disk and flywheel but it does put pressure on the front thrust bearing and over time or extreme PP torque ratings will cause play in the thrust bearings and may and I have seen on several occasions the rear thrust bearing just fall into the oil pan on both V160's as well as 154's this is the reason for the clutch delete as well as most high hp supra guys going to multiple plate clutches for less extreme pressure from the plate and the ability of the 2,3,4, disc configurations to handle the HP
I had heard this exact same thing on the v160 and r154 because they are the pull setup.
do you know if the w58 has this same problem being a push type?

I remember a very similar thread and there was a nice explanation/answer in post 15.
http://www.clublexus.com/forums/perf...-na-t-w58.html
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Old 06-05-12, 04:48 PM   #29
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I had heard this exact same thing on the v160 and r154 because they are the pull setup.
do you know if the w58 has this same problem being a push type?

I remember a very similar thread and there was a nice explanation/answer in post 15.
http://www.clublexus.com/forums/perf...-na-t-w58.html

I unfortunately have no experience with that particular set up but I would summarize by saying that there are thrust bearings on both sides of the cap to control movement of the crank (crank walk ) and in theory would be possible on any type of clutch configuration but most likely more predominant on the turbo based transmissions due to the constant upgrades in theses particular vehicles, heavier clutches, from the requirements of our insatiable thirst for more power.
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Old 06-05-12, 09:37 PM   #30
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Now can we get back to the OP's original conversation!!!
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Last edited by 99SC42; 06-06-12 at 09:41 AM..
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