Throwout Bearing Shim?

sdleo29

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When I did my 6060 there was no shim behind the TB of the tranny I bought, but on my 3650 there was a 1/8" shim behind it. I was wondering what dictates whether you need one or not? I can see the bell housing is much deeper in the 3650, but does it matter what clutch you use?

I have a spec 2+ going back in, just changed out plate on flywheel and got a 26 spline disc; the clutch had only 3k miles on it, so I felt I didn't need to change the pressure plate.

Thanks
 

Department Of Boost

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The slave should be pre-loaded correctly.

-Measure from the block/trans mounting surface to the tips of the "finger springs" on the pressure plate.

-Measure from the mounting surface on the bell housing to the "face" of the slave.

-You're going to need to account for the thickness of the "bell housing spacer/plate" into one of the above measurements. Or just put in on the block and do the first measurement with it already on there.

-Take your two measurements and see how much pre-load is being placed on the slave when the trans is bolted up. You want about one inch.

-Shim for goal

Depending on a lot of things I have run shims anywhere from 1/8-1/2" to get things right.
 

eighty6gt

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Hey,

How'd you get the 1" # - did you dismantle a factory fresh car?

I'm going to just get shims made when I do my clutch/trans. I'm machining the flywheel, start with that thickness, if it's anything substantial.
 

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Hey,

How'd you get the 1" # - did you dismantle a factory fresh car?
I do that when the trans is out of the car. Every time I do a trans job.

I'm going to just get shims made when I do my clutch/trans. I'm machining the flywheel, start with that thickness, if it's anything substantial.

So you're saying that you're going to surface your flywheel and whatever you took off your going to make a ship that thick?
 

sdleo29

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I have about 1.125 , without considering the bell housing spacer plate as you call it, did you mean the flywheel cover that sits on the locating pins between trans and back of motor? If that's the case I should be within 1/16 assuming 1" is optimal.
 

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I have about 1.125

without considering the bell housing spacer plate as you call it, did you mean the flywheel cover that sits on the locating pins between trans and back of motor?
Correct.


If that's the case I should be within 1/16 assuming 1" is optimal.

What is the distance from the block to the pressure plate fingers? This is tricky to measure because the fingers are "in" the pressure plate. So you need to measure from the block to the pressure plate "face". Then measure from the pressure plate face to the fingers and subtract the second measurement from the first. If you can give me both of those measurements.

What is the distance from the bell housing mounting surface to the slave?

How thick is the flywheel cover spacer plate thing?
 

eighty6gt

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I do that when the trans is out of the car. Every time I do a trans job.



So you're saying that you're going to surface your flywheel and whatever you took off your going to make a ship that thick?

Seems reasonable, the PP/etc will move towards the engine by that distance.

I meant how you got the 1" as a specification - I'd assume an unworn factory flywheel, new PP and disc gets you 1" of preload. I'm probably needlessly paranoid about needing a small shim due to the flywheel material removal, but it seems like so many people have clutch issues.
 

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Seems reasonable, the PP/etc will move towards the engine by that distance.
It is reasonable, but that assumes that the slave had enough preload to start with. I have yet to see one that did.

I meant how you got the 1" as a specification
Years of experience. Understanding how the system works (or should) and the input from some very smart/experienced people in the industry.

Funny story. My buddy who is an engineer at SVT was over a few weeks ago when our S550 got a T56. I had him help measure so we could make a shim. I explained what we were doing and why and he thought it was interesting. Monday morning he calls me from work to explain it in more detail to him so he could pass the info along with his co-workers. The guys at SVT are now using this method when setting cars up.

- I'd assume an unworn factory flywheel, new PP and disc gets you 1" of preload.
No

I'm probably needlessly paranoid about needing a small shim due to the flywheel material removal, but it seems like so many people have clutch issues.

You need a shim to make it work as good as it can work. And it will be a lot thicker than what you removed from the FW.
 

sdleo29

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Correct.









What is the distance from the block to the pressure plate fingers?

rough and tough about 3- 7/16


This is tricky to measure because the fingers are "in" the pressure plate.

Yes agreed, I assumed this to be negligible, it's roughly less than 1/16 but that is by eye, left calipers at other house.



What is the distance from the bell housing mounting surface to the slave? 2- 5/16



How thick is the flywheel cover spacer plate thing?
. 1/16 - 3/32


How critical is this, is more preload more or less desirable ,or is it just as bad to be more than less? I know I am within .0625 and .125 of that 1", high side that is
 

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. 1/16 - 3/32


How critical is this, is more preload more or less desirable ,or is it just as bad to be more than less? I know I am within .0625 and .125 of that 1", high side that is

There is a lot of wiggle room. You could be .250 +/-. I would go toward more preload than less though.

You're looking good.
 

eighty6gt

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ah, so the factory was wrong.

I wonder why people like the 2013 GT500 master. Hoping you don't wind up with excess travel with the master and a heavily preloaded TO bearing assembly.

I can't believe the pressure plate fingers can be preloaded by an inch and the clutch isn't disengaged. Also that the throwout bearing will run at engine rpm for the duration of vehicle operation, with no outside lubrication.

https://www.youtube.com/watch?v=K4Y0PoUdG3A Unrelated video, but does indicate constant engagement. (read the comments for tech regarding a single disc swap on a GT500. 1" taller throwout stack.) I also found that idling a bearing at engine speed is easier on it than accel/decel to and from 0. I suppose bearings such as the ones in the FEAD are sealed and do experience high loads, and they do OK, at higher than engine speeds.


https://youtu.be/qrF0BBgSv4Y

here's a ram video, .150" clearance on a single disc, no preload.
 
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Department Of Boost

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ah, so the factory was wrong.
I've never measured what the factory preload actually is. But keep in mind that their setting is based on using OEM parts. When you throw aftermarket stuff in factory settings go out the window. For example, Ford knows how much the fingers "take a set" which directly effects preload. Who knows what the individual aftermarket stuff does?

I wonder why people like the 2013 GT500 master. Hoping you don't wind up with excess travel with the master and a heavily preloaded TO bearing assembly.
Most people like things because of internet fashion. Rarely do I see things based on actual science/testing.

It's impossible to have excess travel.

I can't believe the pressure plate fingers can be preloaded by an inch and the clutch isn't disengaged.
You don't preload the fingers. Yop preload the the slave.
 

eighty6gt

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Ah, I see what you mean now.

Thanks for all the info!! I'd have felt stupid installing a .020 shim. Regarding the master cylinder, I haven't yet compared them but I have to assume the 2013 has a larger bore, with all of the attributable benefits.
 

eighty6gt

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Actually measured the installed components today.

Exedy slave to bell surface = 68 mm
block surface including steel plate to pressure plate rearmost extent: 82mm
pressure plate rearmost extent to clutch fingers = 4 mm

82 - 4 = 78

78 - 68 = only 10mm or around 3/8" preload.

I'm adding a 3/8" shim. What is interesting is this will completely bring the slave's locating outer feature outside of the transmissions male feature. I will have to eyeball the slave so it is reasonably concentric on the clutch fingers (who cares, as long as it misses the input shaft - the bearing rotating surface is not even concentric to the inner sleeve. I'll get a photo later.
 

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