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Resurfacing the flywheel gives people a false impression.
All of those original black "hot spots" are still there, because the metal has actually changed hardness in those locations. After a few miles of use, all the hot spots will re-appear. The grinding process just smears the harder and softer areas all together so that they look nice and the surface is flat. (Which is why they grind them with a stone....turning one in a lathe (like was done when the flywheel was made) is impossible....even the best carbide tooling just bounces off of the hot spots.)
Regardless of that, what you are trying to accomplish is to replace the clutch pieces as needed to have it hold the power (easy to accomplish, with a new disc) and be smooth (these single disc clutches are very forgiving, when properly lubricated and installed.)
The biggest problem with these clutches occurs when people try to mix early and late T/O arm and T/O bearing pieces.
The rule to remember is that the T/O bearing and the T/O arm must have one "crowned" surface and one flat surface. Both crowned....bad. Both flat....terrible.
Greg,
I'm trying to understand what you are saying here.
My flywheel was and is fairly flat. So resurfacing did not buy me anything? I could have reused it? The machinist did say that those spots were very hard and could not be removed.
Are you saying to buy a new flywheel or if the old was was straight, just reuse it?
So a new clutch (friction) disk and all parts properly lubricated is most important.
As well as not mixing new and old TO bearing and release levers.
My local bearing guy kind of chuckled at me when I showed him this bearing.
So If I would like to reuse my -07 arm and guide tube,
- I need to buy a new TO bearing assembly and replace the bearing in my assembly or
- Buy the new bearing, arm and guide tube?
I'll have to look for the crowned and flats of a T/O bearing and T/O arm.
the TOB bearing I greased/modded , I was clearly able to see a bearing shield your part doesnt appear to show this,
so you are in for a new bearing ,
As Greg said make sure to match the new TOB and release arm and guide tube the new parts should all be GTS parts
Biggest issue here was the missing ball cup.
Why not replace the bearings, lubricate the shaft with the proper sticky grease, and put it together and drive it.
Not a lot of downside.
If it doesn't feel right, its easy to go back in.
Doesn't roger have a rebuilt bearing for the s4/gt?
I'm trying to understand what you are saying here.
My flywheel was and is fairly flat. So resurfacing did not buy me anything? I could have reused it? The machinist did say that those spots were very hard and could not be removed.
Are you saying to buy a new flywheel or if the old was was straight, just reuse it?
So a new clutch (friction) disk and all parts properly lubricated is most important.
As well as not mixing new and old TO bearing and release levers.
My local bearing guy kind of chuckled at me when I showed him this bearing.
So If I would like to reuse my -07 arm and guide tube,
- I need to buy a new TO bearing assembly and replace the bearing in my assembly or
- Buy the new bearing, arm and guide tube?
I'll have to look for the crowned and flats of a T/O bearing and T/O arm.
Thanks,
Ken
Not trying to rain on your parade....just throwing out information in my usual abrupt way.
Your flywheel should be fine....I reuse them until they turn blue on the backside, which means they are "heat treated" all the way through. (I have them surfaced, too, when they are not smooth.)
Just making the point that pretty reground flywheels are still full of hard hot spots in a relatively soft base material and regrinding them is a false sense of it being like new. There's "ugly" under that pretty surface, still.
As long as you re-use your original T/O arm and T/O bearing, you will be fine. If you buy a new T/O bearing, you will need an 09 arm and a new T/O collar....no other option. You can not combine the curved surface of the 07 arm with the curved surface of the new style T/O bearing.
It's amazing how often this^^^^is messed up and has to be redone....and you have to be a stinking Ninja to get the clutch back out and get the arm off of the pressure plate and T/O bearing, because both curved surfaces take up all of the "extra" space.
There's a factory service bulletin on the T/O bearing/arm supercession. I'm sure someone here can post it, for prosperity.
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
You may be onto something here. I have looked at the tech bulletin and I appear to have the new style TOB and guide sleeve.
The tech bulletin references the TOB ID with the polyamide inserts at 32 mm, I measure 32.2 to the high sides of the inserts.
The OD of the guide tube is supposed to be 31.8 mm and that is what I get.
I do have the old -07 arm that may have been modified. I guess I need to get a -09 arm or verify the modification to this arm for function.
Stan,
Maybe this is why I could not service the bearing, it is probably the new style.
The saga continues. I have a stack of previous owner service records and none of them mention this work.
Your original problem was not the clutch itself but the hydraulic system or the release arm mechanism that disengages it. You said the car would launch forward when cold starting the engine, the slipping marks on the flywheel and pressure plate show this. So, you still have to figure out why the clutch wasn't disengaging or you'll be back to square one.
Yes, I am working on trying to figure this out with the help here.
I believe the hydraulic system is good. I verified the full operating travel of the slave rod, per the WSM.
Your original problem was not the clutch itself but the hydraulic system or the release arm mechanism that disengages it. You said the car would launch forward when cold starting the engine, the slipping marks on the flywheel and pressure plate show this. So, you still have to figure out why the clutch wasn't disengaging or you'll be back to square one.
What I have found is that I was missing the release arm ball cup. I think that could have been contributing to the problem. With that missing the clutch would not have released as far as designed to.
The old release arm (-07) was used with updated TO bearing and guide tube. The release arm is thicker / wider where the bearing sits, this would make dis-assembly/assembly more difficult? Not sure how this would affect the clutch operation?
The -07 arm was milled some and not evenly, to accept the later style bearing. There may have been a little sideways drag or pull, I'm not sure if that would have affected the clutch operation.
The PP fingers and the short shaft splines did not have any visible lubrication on them. This could have affected the ability of the clutch disk to slide on the short shaft.
The previous PO did not do any work directly on the car, to my knowledge. The clutch work would most likely have been done by a shop.
I think the biggest contributors to the issue I was having were the missing ball cup and lack of lubrication.
If the clutch disk did not slide well on the short shaft and if the combination of the ball cup and the -07 arm and new style TOB and guide tube impacted the clutch separation, this could have caused both the occasional lurch on cold startup and the occasional slipping that I could not reproduce on demand.
Right now my plans are to;
Replace the pilot bearing
Replace the rear crank seal
I did get the flywheel surfaced
Get a new -09 arm
Get a new TO bearing
Get the proper grease and properly grease the clutch parts
Reuse the clutch disk
Reuse the PP
edit -- get a new ball cup
as Landseer said
Biggest issue here was the missing ball cup.
Why not replace the bearings, lubricate the shaft with the proper sticky grease, and put it together and drive it.
Not a lot of downside.
If it doesn't feel right, its easy to go back in.
Malcolm,
Thanks for the link, I had not read that one yet. But I had seen similar information.
It's not the missing ball cup. I've seen ones that were missing and the clutch still worked normally. Is the arm milled or was it "machined" by the release bearing? Hard to tell from your pictures.
You may be onto something here. I have looked at the tech bulletin and I appear to have the new style TOB and guide sleeve.
The tech bulletin references the TOB ID with the polyamide inserts at 32 mm, I measure 32.2 to the high sides of the inserts.
The OD of the guide tube is supposed to be 31.8 mm and that is what I get.
I do have the old -07 arm that may have been modified. I guess I need to get a -09 arm or verify the modification to this arm for function.
Stan,
Maybe this is why I could not service the bearing, it is probably the new style.
The saga continues. I have a stack of previous owner service records and none of them mention this work.
Thanks,
Ken
Yes, you have the wrong mixture of parts. The T/O arm has been hitting the fingers of the pressure plate because the two curved surfaces pushes the arm too close to the pressure plate.
Is the arm milled or was it "machined" by the release bearing?
I honestly do not know. I am not sure what a new -07 arm looks like. There are milled areas on the engine side of the arm. They are not evenly milled on each side. Then the shiny areas where the TO bearing has caused some wear during use.
From other threads I have read this miss match of parts could have been why it was a little difficult to get the arm off of the ball.
02-08-2016, 11:40 PM
