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Bottom line question. Can the flywheel be put on wrong as in not rotationally in the right location? If I recall correctly there is a metal locating dowel and the flywheel will only go on one way.
Full story - 1995 Z28, T56. The last time I had the engine/trans out I decided to replace the flywheel and clutch assy. Old flywheel had been resurfaced a couple of times but was doing ok.
I got a stock flywheel and clutch kit from NAPA (where I work so employee discount). Put it all together. I also purchased and installed Hawks Third Gen's adjustable clutch master cylinder and their clutch fork as mine had snapped into two pieces which is what began this process.
The car shifts and pulls great however, I now have a vibration that I didn't have before. I thought it was u-joints so I had them replaced by a machine shop. BTW I have the aluminum drive shaft not original steel one. BTW-II the pilot bushing was not replaced.
When the u-joints didn't fix the problem I thought to rev the engine in neutral. Vibration at roughly 2,000 rpm and multiples. So it's something with the engine...whose internals are stock. I'm assuming it's something I did or didn't do on the flywheel clutch installation or, of course it could be an out of balance flywheel or pressure plate.
So open to suggestions. I'm sure I'll have to pull everything again but would like to have an idea what to look for.
Again, clutch engages/disengages fine, doesn't slip on a hard pull, no noise coming from anywhere but especially not the bellhousing.
getting a stock replacement FW and clutch kit should be plug and play. With that said...most of these FW's & clutch kits are offshore made and the PP on most clutch brands do not have any balance holes in some of the 3 PP surface tabs nor do they have the paint dab on PP that you would line up with, or as close to, the dowel on the crank.
Stock LT1 motors are externally/rear balanced. The stock FW should have a cast in weight on back side and typically a few large drill counter sink type holes somewhere on the back and or pins placed in the outer holes of the FW
If the crank no longer has the dowel you just line up the FW so that hole lines up where the dowel would go if it was missing.
you can either pull the starter or drop the dust cover off bellhousing and have someone rotate engine by hand to see if the cast in weight is there. I have never seen a replacement stock FW without one though
for the purpose of this pic I positioned the PP & FW to show balance holes on PP and pins used to "zero" balance a stock FW after the cast on weight was ground off for my INTERNAL (not stock) motor. The blue paint marks on both PP & FW would be positioned to line up on assembly. This is just an example of how a PP is balanced from the manufacturer....not something many China made PP have anymore.
I have seen when a PP got dropped it skewed the angle of the PP hat and diaphragm. Happened to a SPEC kit I got with shipping damage. I visually saw something "off" when I took it out of box and called SPEC who promptly sent another and tech said "yeah that kit would have shook like a dog shiating razor blades"...so just throwing that out there as a possibility.
Question came to me showing I'm not fully understanding. If the correctly made flywheel is off the engine and tested for balance, should it be in perfect balance or is it supposed to have an eccentric weight on it that balances out the rotating assy of the engine?
The weight on the flywheel compensates for the material removed from the design of the rear flange of the crank, to provide for the installation of the 1-piece rear seal. If you spin the flywheel by itself, it will be out of balance and shake.
The 1-piece RMS flywheel has a smaller 3” bolt circle, compared to a 3.58” bolt circle for the 2-piece RMS flywheel. So they can’t be accidentally interchanged. A truly stock 1-piece flywheel is going to have the weight cast in. But aftermarket units may have a bolted on weight.
OK guys, after 9 months I've finally gotten the transmission out to get this fixed. I've got pictures for your review. I see on the PP that there is a yellow mark. Following Chimera's comment I should align that with the flywheel dowel pin.
Is this clutch marked correctly as to which side faces the flywheel. My Haynes says to put the damper springs facing the transmission which I would interpret is backwards from the label on this clutch. I did install it as the clutch plate indicated.
I didn't notice where I had the PP paint mark before I removed it.
Clutch plate I installed last Sept. Notice it says Flywheel Side.
This is the flywheel I installed last Sept. It has the weight at 9 o'clock and also some drilled places at 12 o'clock.
This is the current flywheel front (transmission) side showing.
This is the flywheel mounted on the car before I removed it. the crank has the dowel pin in place.
Flywheel side of the current pressure plate.
Transmission side of the current pressure plate. From a previous post I'm following that the yellow mark, at 12 o'clock,should be aligned with the dowel pin as closely as possible.
This is the backside of the old flywheel. I notice it has a metal pin, at 3 o'clock, in one of the outside holes that the replacement flywheel doesn't have.
Reminder of problem. A vibration when the engine is rev'd at about 2,000 rpm in idle or while driving.
I didn't replace the pilot bearing last Sept. I have a new one to put in now. The new one has roller bearings as opposed to the oil infused bronze bushing. Are the ones with actually bearing better? that is will I recognize any improvement or different feel? How well do the roller bearing pilot bearing last typically in a daily driver? Worse or better than the bushing.
Your clutch & FW pics look fine. The spring hub part of the disc goes towards FW. Sounds like you have installed everything right
The pin in the outer hole of the old FW was used in balancing. Some FW may have none
I have replaced several clutches and FW's without any balance issues on stock motors (internal balanced). Weird you are having issues on a stock motor but "maybe" the replacement FW is just off...although it does have the cast in weight and other drilled balance holes
Possible the pilot bushing is worn and the cause of the vibration. The bearing type is stock and recommended by Tremac. They should last 100k mi without issue
Given your FW & clutch look good and a pilot bearing replace and you still get a vibration....confirm your exhaust or anything else is not "grounding" against things like X member which would send vibrations into car
FWIW this blind hole puller makes removing old pilot bushing plug & play. Its at Autozone on their loan a tool deal. #27128
Thanks for the confirmation. The pilot bearing is being a pita coming out. I'll see if my nearby AZ has the tool you recommend. Last time I tried to use the puller with the two arms and I broke the tips off. This time I've tried grease and paper to force it out and it's not budging.
The vibration is definitely something with the engine as you can feel it all through the car. I've wondered about putting the old flywheel back on. I only replaced it because I had had it surfaced a time or two and thought my pedal was getting low to the floor. I've since replaced my master clutch assy with the adjustable assy from Hawks Third Gen. So I may go that route to see.
The AZ tool is real easy to use. Just a few good pulls with the slide hammer and out it comes. Harbor Freight also has the same type of puller for purchase
I have resurfaced a stock FW 3 times without issue...but it depends on how much is taken off. They sell shims you put between crank & FW to offset the difference taken off.
I know it is a PIA to do clutch swaps so putting back in the same parts may be concerning the issue will remain
Typically bad pilot bushings/bearings make noise vs vibration. Is the input shaft tip scored or groved??
You could take your old FW and new one to a machine shop and have them match balance the new one to old one. I have never had to do that. I have taken big $ billet "neutral" balanced FW's in to confirm they are zero balanced (for internal balanced motors, not stock ones) to find they were 26 grms off....
09-29-2017, 08:20 PM
