Whoa.... Now I see why you needed a clutch! (saw ya on Amazon)

Thanks for the installation Tips!!

 

The clutch itself didn't seem to be damaged (pilot bearing, flywheel, disk, mechanism all seemed fine) but the slave cylinder wasn't happy. The car originally had 32K miles and I put about 3K miles of racing on it so I wasn't going to take any risk and I changed everything to be on the safe side.





Broken bellhousing and clutch with 35k miles

 

Part # and prices:
- Dorman CS360074 Clutch Slave Cylinder: $68 (Amazon)
- LuK 04-905 Clutch Set: $377 (Amazon)
- ACDelco 12554980 GM Original Equipment Manual Transmission Clutch Housing: $153 (Amazon)
- Bellhousing bolts NOS GM General Motors Chevrolet 11516862: 2 for $10 (eBay)
- Remote bleeder for C5: $50 (new on eBay)
- Level Zero Motorsport Poly Mount (95A duro with .0125" 6061-T6 scuff plates): $132 (eBay)
- HPE C5 Corvette Differential Torque Limiting Mount: $389 (Hoosier Performance Engineering)

Total: $1179 ($608 repair parts and $571 upgrades)

 

Well,,,,,,,,,,,,,,,,,,Every MN6/MN12/T60-60 Corvette engine is re balanced at the engine factory after engine assembly further than an Automatic C5/C6. Manual transmission drivetrains are more sensitive to minor engine out of balance conditions than automatic car are and are further balanced.

Small balance PINS are pressed in the outer rim of the flywheel and the damper was also weight adjusted if necessary and if it needs additional balancing.

When you remove the OEM flywheel,, you are suppose to mark it in relation to how it is factory installed on the crank to maintain that proper balance.

IF,, you change flywheels, and you had balance pins in the old OEM flywheel, you SHOULD have the new fly wheel OFF SET BALANCED to MATCH the old flywheel.

If you don't, you could and usually induce unwanted vibrations in the drivetrain around the 2000-3500 RPM range.



IF, additional balancing was done to you engine,, the new flywheel should be OFF SET balanced to the old flywheel and referenced back to the same clock position on the crank.

Bill

 

You can't really mess up the flywheel position as there is an extra hole for alignment and it can only go one way.

I just went and look back at the old flywheel again:


Back of the old flywheel

There are a number of holes that have been drilled I guess to balance the flywheel. There might be one small pin below the letter N but is this to just balance the flywheel itself.

So I went to research the forum some more and it looks like this has already been discussed here: https://www.corvetteforum.com/forums...post1574050923

The GM manual clearly states that the clutch kit for 1997-2004 LS1/LS6 engines is a separately balanced assembly and is not used to balance the engine. So by replacing the whole assembly, I don't think I will have any issue (and I didn't notice any vibration besides the extra ones caused by the poly motor mounts).

I guess what you call the damper is the harmonic balancer and this is the one that is used to balance the engine itself so that the engine is 0 balanced. The clutch kit is 0 balanced too. I had no reason to remove the harmonic balancer so the engine is still 0 balanced too.

 

ALL GM flywheels are ZERO balanced from the manufacture. The DRILLED holes at different depths are thoes ZERO BALANCE holes

YES,, that one single pin was what GM added to further balance your engine.

Will ONE PIN cause you issues... We will see when you are all back together and back on the road.

That flywheel can be remounted in SIX different positions on the crank. There is NO alignment pin in the crank to fit in that extra hole. If someone at the factory had a bad day and decided that they wanted to mount it one bolt hole OFF of that alignment hole position, it would bolt right in and you would NEVER know the difference.

Bill

 

I don't think I agree with that. The pin is to balance the flywheel/mechanism assembly, not the engine. This is why it is inserted at the back of the flywheel when the mechanism is bolted to the front of the flywheel and the whole clutch assembly is balanced.

If you look closely at the flywheel, you will see that there is a 7th hole. There is the exact same hole at the back of engine where you bolt the flywheel. The 7th hole on the flywheel and the engine were aligned on the old flywheel and I don't think this was a coincidence. The new flywheel also came with that same 7th hole. So I realigned it the same way.

I am already back together and on the road and I haven't noticed any vibration issue.

 

Here is the MASTER clutch balance issue post of all post

Thbwlz is the MASTER on this topic.

- C5 Clutch Vibration Issues: http://forums.corvetteforum.com/c5-t...post1585950971

Read through this entire post... Its an education.

He explains it better that anybody.

Im GLAD you didnt have any noticable vibration issues!

Bill

 

This is indeed a very interesting thread. It doesn't look like I have any weights on my front damper so I might have been lucky that I had a pretty balanced engine in the first place.
There are some minor vibrations in the car but I attribute them to the poly mounts for the engine and diff since it does vibrate at idle. The new flywheel (LS7 style) does not seem to have the same pin holes, so I guess one would have to adjust the balancing some other way for that kind of flywheel.

 

Whoa.... Eye Opener. Thanks Bill! You always seem to be lurking and spreading truth at the right moment.

Mech Eng. here. Now, after spending a lot of time as a freelance mechanic for various exotic cars (in my younger days), I recently bought a corvette (selling my 944) thinking hey, these thing are simple, durable, "Like a rock". Right?
Hmmm, not so. They are finely engineered with a 3rd eye on costs and efficiency. Beautiful.

Back on topic. - I seem to recall GM having a on-car engine vibration analyzer, with indexed input/output? Perhaps there an aftermarket solution, or I need to go build one...

 

It could be that LUK left those holes out as cost savings, since the aftermarket isn't likely to be as demanding as GM. Parts always seem to degrade in quality without the original QC measures and procedures in place.

Now I have to rethink my whole game plan. (or cross my fingers)

Glad it's working out for you Lefrog!

 

I helped a Forum member from CANADA with a severe clutch vibration problem. So severe, that he didn't want to drive his car.

He didn't save the old flywheel and didn't clock the crank for any sort of reference.

I asked him to look for machine balancing businesses in his area and he found a guy that had a mobile machine. The guy came out, hooked up the accelerometers and made it perfect. He added washers under the bolt locations on the pressure plate where weight was needed.

I have also helped a couple of members just add washers to the bolts that secure the pressure plate to the fly wheel. Add a washer or two to ONE BOLT POSITION at a time, run the engine and see if the vibrations get better or worse.

Do that for each bolt position until you find a position that improves the vibrations. Add or subtract washers as necessary to eliminate the issue.

When you have the correct weight under that bolt hole location, remove the bolt and washers and weigh them. Find a LONGER bolt for that hole ( to get the proper thread engagement for that bolt hole) and add washers to match the finial balance weight.

 

The pfadt mounts are available again through aFe Power:

http://afepower.com/shop/details_new...dt&brandID=142

 

I can't believe the vendors on this forum:
1. Read the entire thread, the project is completed and I already provided the part # and prices for what I got
2. Don't send me a PM with your commercial offers, if I need something I will contact you
3. Selling your trans mount at $520 is not a good deal when Hoosier engineering sells it for $389. We shop around and are not stupid.
4. Also a special note for the vendors who advertise continuously in the tech threads, it's annoying and it's even more annoying when you advertise for parts you don't have in stock.

On this note, you all have a good weekend and keep an eye on your bellhousings!

 

1. Sorry, just letting you know that the parts you asked for earlier in the thread are available now. You asked the question. Obviously I hadn't made it through the whole thread.
2. Noted.

The thread is very well documented. I too had a transmission bell housing fail after I backed into a k-rail at 60+mph. All the mounts on that car were OEM. The failure was clearly due to the impact.