Topic: Question about "stepped" flywheel

[scott.475]

Guys, I'm going to order up a Marlin clutch in the next day or two. I know it is important to get the flywheel stepped a certain way, so I am planning on taking it to an actual clutch shop, or at least a shop that has the right machine for doing the operation. Still, I am worried that they might tell me they can do it, but then not do it. I have always been confused about exactly what stepping is, I don't think it as obvious as I think it is. I have always thought that, if the flywheel were flat on a table, face up, and you looked at it from the edge, a certain part of the outside diameter would be cut a little deeper than the inner diameter, thereby causing a "step" between the different cuts. BUT, I have read other things that make me think that it results in more of a "dome" to the face. I just have no idea. Someone please tell me what I need to look for to make sure my flywheel has been cut right.

[79coyotefrg]

  well when i had mine done at the local race shop,  they used a machine to "turn"  the flywheel as the cutting head milled it on one side,  as it was turned  it was milled all the way around,  this left a kinda half moon shape all the way around the flywheel,  the took off .050

[FIREBALL]

Any reputable clutch/trans shop that surfaces flywheels should know exactly what to do. Shouldn't be an issue at all. When you pull the FW off it will be obvious. The surface that the disc makes contact with is raised above the surface that the pressure plate bolts to. Don't worry about it. Look at it befor you take it in, and when you get it back make sure there's still a step on the face.

[lowgeared]

Call me a cheap ass...but on all three of my rigs with manuals they are running "custom lowgeared" 400 grit palm sanded flywheels.  Not only free, but never had a clutch slip a day in my life.   

[Marlin]

From the factory, the pressure plate was designed to work with a stepped flywheel that has a .018" to .020" raised area for the disk surface.
Thur the years, and doing many, many many.... clutch jobs, I found out that by increasing the step to .026", this will wake up the clutch performance

Insist on having the flywheel machined using a fluid cooled stone grinder type machine. It cannot be machined on a lathe or any other machine.

The three 8mm dowels must be removed and both surfaces ground. Remember to insist on a .026" step.
It cannot have a domed face. It must be a flat true two step surface.


Marlin

[scott.475 [OP]]

Fireball and Marlin, perfect, thanks! The .026 steps makes the pressure plate sit closer to the flywheel, I finally get it!

[Fireimp141]

so a .18 to a .26 step? alright

[Skinny_Pedal]

so a .18 to a .26 step? alright

yes

[scott.475 [OP]]

so a .18 to a .26 step? alright

yes

Marlin says .026, a big difference from .26. He is consistent in several posts that it should be 26 thousanths, NOT 26 hundredths

Here are the other posts I found: http://board.marlincrawler.com/index.php?topic=3512.0 http://board.marlincrawler.com/index.php?topic=2723.0  http://board.marlincrawler.com/index.php?topic=4105.0 (3rd post from end, reply #18) http://board.marlincrawler.com/index.php?topic=4803.0

[BigMike]

so a .18 to a .26 step? alright

Well actually the 0.026" is the actual difference between the two surfaces. The person who is surfacing the flywheel only has one measurement to decided on. The two surfaces are the clutch's frictional surface and the surface that the pressure plate bolts down on. Therefore, if these two surfaces have a greater difference, ie the clutch friction surface is higher than the pressure plate bolting surface, then the area between the pressure plate and the flywheel is decreased, so the clutch is in effect tighter.

The effect of this will be that the actual friction "point" on the down travel of the clutch will be moved higher. That's how you can tell if your clutch is worn out. A new clutch should have a friction "point" of somewhere near the end of the clutch pedal movement, and a badly worn out clutch will have a friction "point" almost at the very beginning of the clutch pedal movement.

As the clutch disk wears, it gets thinner, and less expansion between the flywheel and the pressure plate is needed in order to release the clutch; in this case your foot doesn't have to really press the pedal down so far and the clutch is already disengaged.

So by surfacing the flywheel beyond what Toyota recommends, you are placing the pressure plate closer to the clutch disk, so more clutch pedal movement is required to disengage the clutch.

Now this is good for the following reasons:

• The clutch will last longer because these is less space for it to work with, so it will still be working even when it is badly worn and very thin, it will still work.
• Since the space is decreased yet the clutch is still the same thickness, the pressure plate will actually "grip" the clutch at a higher level of force because the springs in the press. plate will be displaced at a greater distance. Spring rate is equal to the spring constant x distance. So the more the pressure plate is "opened" the greater the spring force. So with the flywheel surfaced at a greater difference than what Toyota recommends, now the pressure plate has to open up more to "let go" of the clutch.
• The above reason amounts to better gripping force from the pressure plate, so the clutch Performance is increased due to more friction, as Marlin said in his post above.

The only bad thing about doing this is that when you first do it and your clutch is fresh and thick, the clutch pedal will have to be pressed almost all of the way to the floor just to release the clutch. This is great because the clutch frictional pressures are greater, BUT, this means that it will be more difficult to speed-shift (hehe if you even do that with a truck ) and if you have a bad habit of not pressing the clutch pedal all the way down before shifting, then there will still be some friction on the clutch disk, and when ever you shift, the synchros need to change the speed of the input of the trans - which is connected to the clutch disk right? So if you only press the clutch pedal down about 60% when it really needs ohh say 80% to really completely release the clutch disk, then the clutch isn't completely released, and when you shift, the synchros will be trying to change the speed of the clutch disk and of course the frictional forces still acting on the clutch disk are pretty high for a little synchro to act against, so this can be very detrimental to your transmission shifting performance if you do not use the clutch correctly.

And through all of the many years of experience, Marlin has found out that the flywheel surface difference of 0.026" offers the best clutch performance while still being able to disengage the clutch disk from the drivers seat. For instance, if you were to try, or say 0.030" or something, when you put it all back together, it's likely that even with the clutch pedal all the way down to the floor, the clutch could still be engaged and you would never ever be able to shift at all if the engine is on or if you are traveling at speeds greater than 5mph or so.

So surface your flywheel to 0.026" and be happy with the results!
BigMike

[FIREBALL]

Boy your long winded. Did you get that from your dad?

[BigMike]

jealous

[brainlessfool]

Well I for one would like to welcome the retrun of "tech master mike"

 a fitting replacement for the viking cat overlords!


          ---> bf   <---bm

[KYOTA]

viking cat overlords!
 

Dont start that crap again 

[brainlessfool]

what? you dowt the power of the Viking cat overlords? 

[88runner]

here we go again

[BigMike]

[FIREBALL]