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Discussion Starter · #1 ·
Well we are onto the next step in the investigation of why I have lost two thrust bearings on a new engine break-in. Both times the engine was installed in the car with everything attached. The thrust bearing did not wreck until the clutch was applied.

Since then engine was successfully broken in on an engine dyno effectively ruling out the engine as the source of the problem.

So the next step is to find out what the problem is. From inspection, it's not the T5. So what we are left with is the JMC hydraulic clutch, the SPEC stage 2 disc and pressure plate, and the Mcleod scattershield.

The mechanic thinks the scattershield is warped, from inspection it looks fine, but you never know.

Your help and thoughts would be deeply appreciated as I can't afford to wreck another thrust bearing.

Steve
 

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Scattershield warped? Seems like that ought to be an obvious flaw. Some feeler gauges and a straight edge should confirm that pretty quick.

You have checked the shield for alignment with crank center?...they have technique for 'How-to" included in the box, you can pull it from the 'Net if you can't find documentation. Either the vendor or some place like Summit will have off-set dowels that let you adjust alignment.

that doesn't sound like an issue that would cause thrust bearing wear...but then, I'm not a machinist. Do you have a mechnical or hydralic linkage...is it possible that lever is over extending?

I can understand your trepidation, apprehension after two failures. One thing about Ford guys...we don't seem to mind working for the glory!

** Sorry about the big words, I guess I could have used "dread"?
 

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Well something has to be pushing the crankshaft forward.

I would mock it up without the clutch assy. Just the flywheel, bellhousing and transmission.

Sounds like the transmission input shaft is a bit too long.

Is the pilot bearing correct?? Installed correctly??

After bolting it together, sans clutch, see what you have for thrust clearance. If you haven't any, well there is your problem.

<font size=-1>[ This Message was edited by: Gearhead99 on 10/7/06 1:33pm ]</font>
 

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With the hydraulic throw-out brg I would say you have a problem with it. First - is it adjustable - some are some are not. Check how far it can travel and how far it needs to travel - If it can travel too far then you are probably using hydralic force to ruin your thrust brgs. Either adjust it so it won't over travel or limit the actuating rod so you can't over travel the master cyl.
Paul
 

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Lots of good ideas above. Something is making the input shaft of the tranny push forward.

Driveshaft length can also cause the crank to be pushed forward. Even if the car hasn't been moved, the driveshaft yoke can cause a bind. You must check slack with all wheels on the ground (or on jack stands) and there should be about 1" of remaining forward movement available.
 

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I feel your pain. I destroyed the thrust bearing in my 331 stroker in the first 500 miles, but I did it w/ an automatic. My issue was that the converter was pushing the flexplate into the back of the engine because I was using all aftermarket stuff and I didn't check my clearances figuring everything would be okay (I was just bolting a trans up). After getting it all fixed, the soulution was using two of those metal plates that go between the engine and transmission (the one's that mount the starter, forget what you call them) and it spaced the converter and flexplate far enough back so that they are not pushing against the crank. Wish I would have checked this before, but I guess it's just another one for the books.
 

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Discussion Starter · #7 ·
Thanks for the input fellas. We know the T-5 shaft is not pushing forward as the crank endplay remains constant with the assembly attached. I have a hydraulic slave cylinder not a throw-out bearing and it is fully adjustable. We have insured quite a bit of clutch freeplay.

The driveshaft has been meaured and checked and statically, the crank endplay remains constant.

The bellhousing is slightly warped,

Keep the ideas coming, they are much appreciated.
 

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Bolt the trans up to the engine with the clutch/flywheel removed.

Reach up in there and feel for free rotation of the input shaft of the tranny.

Also, and this may have already been covered in the last round of thrust wipeouts, is all of the bearing material being cleaned off of the crank after the thrust wipes? As in being re-polished? Is the #3 main web OK? Have you tried to increase the endplay to .010 or so?

Greg
 

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Discussion Starter · #9 ·
On 2006-10-07 08:58, GregP wrote:
Bolt the trans up to the engine with the clutch/flywheel removed.

Reach up in there and feel for free rotation of the input shaft of the tranny.

Also, and this may have already been covered in the last round of thrust wipeouts, is all of the bearing material being cleaned off of the crank after the thrust wipes? As in being re-polished? Is the #3 main web OK? Have you tried to increase the endplay to .010 or so?

Greg
Hi Greg,

The crank was rechecked and was fine after the bearing failures. This last rebuild, we now have the crank endplay at .008 instead of the initial .006. to allow for more clearance. #3 web appears to be true and clearance is consistant on rotation.

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<font size=-1>[ This Message was edited by: DrStang on 10/8/06 1:58am ]</font>
 

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Its them Gremlins,... I tells ya', its them alright. Them Damn Gremlins. Yup. They's all over the place. They'll git c'ha, then ya'll a believe me.

"Miner Pete" - 1852, just before he disappeared in the Sierra's.
 

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Hey ive got a wild idea.
Im no expert by any means in the manual trans area But is it possible that Under power that something is moving forward in the trans and pushing against the thrust??? Since youve checked everything under the sun staticly.
Maybe its time to entertain some other ideas. Maybe swap another T5 trans in this time ?? Or maybe tear into the box and check some clearances ??
I dont know but id HATE to see you trash another thrust bearing. Im sure if your like me that after 3 rebuilds that youd probably be out of money and patience (I can hear that 1/2 craftsmen breaker bar hitting the other side of the garage now)
GOOD LUCK
Robert
 

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I take it the front face of the thrust bearing is the one that is failing right? That would mean that the crank was being forced forward into it. I have seen this happen with very high load clutches in drag motors but street clutches don't typically have that kind of loading. Is the bearing getting proper lubrication? Have you checked the clearance on the rods for end-play? (journal to crank) Are you running a gear drive? Are you using the steel plate between the bellhousing and block (ie:block plate)? Are you checking the clearance at the thrust bearing with the clutch and tranny bolted up? Is your cam thrust plate in place? Is the crank radius small enough that the bearing is not draging on the journal radius?
Paul
 

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Discussion Starter · #13 ·
On 2006-10-08 01:54, PaulS1950 wrote:
I take it the front face of the thrust bearing is the one that is failing right? That would mean that the crank was being forced forward into it. I have seen this happen with very high load clutches in drag motors but street clutches don't typically have that kind of loading. Is the bearing getting proper lubrication? Have you checked the clearance on the rods for end-play? (journal to crank) Are you running a gear drive? Are you using the steel plate between the bellhousing and block (ie:block plate)? Are you checking the clearance at the thrust bearing with the clutch and tranny bolted up? Is your cam thrust plate in place? Is the crank radius small enough that the bearing is not draging on the journal radius?
Paul
Thank you for your input,

I assume the bearing is getting proper lubrication, The engine is always started with the clutch pedal free. The clearance is constant with the tranny and clutch bolted up. Block plate is being used. The other questions I can't confirm but I assume are fine as the engine was dyno'ed on a stand and survived 3 days of pulls.
 

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Is there any way that you can run the engine with the tranny and clutch bolted to it and depress the clutch pedal and then take the pan off to check the thrust bearing wear? If it is ok until you shift gears it has to be the clutch putting pressure on the crank pushing it forward against that thrust surface.
If you can find a way to measure the crank end play while operating the clutch you might be able to trace down the exact cause and find the cure.
Paul
 

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If you push the crank forward, wouldn't the "rear" thrust be worn, not the "front"?? The thrust is mounted on the block, not the crank.
 

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Discussion Starter · #16 ·
On 2006-10-09 19:14, Gearhead99 wrote:
If you push the crank forward, wouldn't the "rear" thrust be worn, not the "front"?? The thrust is mounted on the block, not the crank.
Yes it's the rear of the thrust bearing - crank face

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<font size=-1>[ This Message was edited by: DrStang on 10/10/06 11:07pm ]</font>
 

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Dr.Stang,get on with another build!! This dilemma is costing DOLLARS!! Never heard of a thrust bearing failing soo much and you keep going at a fix!! With a THRUST bearing failing so many times the PROBLEM should be obvious!!Man,scrap your current build and START completely over with another build!If it was a driveline problem,I think the clutch would not engage if there was a CLEARANCE problem!! Just NEVER heard of this situation and you trying to repair it soo many times!!! JUST my 3 cents!!
 

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Discussion Starter · #19 ·
On 2006-10-10 17:29, ran347nosgt wrote:
Dr.Stang,get on with another build!! This dilemma is costing DOLLARS!! Never heard of a thrust bearing failing soo much and you keep going at a fix!! With a THRUST bearing failing so many times the PROBLEM should be obvious!!Man,scrap your current build and START completely over with another build!If it was a driveline problem,I think the clutch would not engage if there was a CLEARANCE problem!! Just NEVER heard of this situation and you trying to repair it soo many times!!! JUST my 3 cents!!
Just about there my friend... this is the last kick at the can.
 
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