The Stovebolt Site Forums The Shop Area Driveline Flywheel/pressure plate balance?

Hey all,

Looking at the flywheel, pressure plate, and pressure plate housing for my 41 Chevy...all of them have been drilled for balance. I indexed the pressure plate and housing so those are good. How do you index a PP assembly that was not original to the flywheel. The maintenance manual makes it very clear that the "x"'s on the PP and flywheel match.

What to do?

Thanks,

Paul

Most replacement clutch covers are balanced during the manufacturing/rebuilding procedure so don't worry about how it's installed. I'll bet there have been at least a few clutch changes on that rig since 1941!
Jerry

Jerry,

Yeah it has many different parts: Engine, crank, flywheel and pressure plate. I was concerned that if the heavy/light sides on each component could add to new out-of-balance issues. I will treat them as individually balanced components.

Thanks for the intel.

Paul

Fortunately, inline 6 cylinders are very well-balanced naturally. It's not even necessary to use "bob weights" when spin-balancing the crankshaft due to the counterweights being spaced at 120 degree angles. Can't get away with that with a 4, a V8, or a V6 engine! As long as each rotating part gets balanced individually, the accumulated errors when the parts are assembled generally doesn't add up to enough to cause a significant amount of vibration.
Jerry

I once had a 1991 GMC truck.
The pressure plate failed.
The clutch pedal would go to the floor, but the clutch wouldn't disengage.
I shut off the truck and stuck it in 2nd gear.
I started the truck and it took off down the road.
I pulled into the nearest GM dealer.
They put in a new pressure plate, clutch, throw-out bearing and resurfaced the flywheel.
After driving the truck awhile I noticed a vibration.
With the truck parked and in neutral if I pressed the gas pedal slowly,
gradually increasing RPM, I could feel a shake in the gas pedal.
I told the GM Dealer that did the repair about it.
They told me that I drove the truck to their garage and they have
no way of telling if the truck had the vibration before the repair.
I complained to the owner of the dealership and he said if they took it all apart
again and nothing they did was wrong, I would have to pay for the labor.
I said do it and that it did not vibrate before the pressure plate failed.
Well, it ended up that the New Genuine GM pressure plate was 18 grams out of balance.

The service adviser told me they asked the machine shop that resurfaced the flywheel,
to check both the flywheel and pressure plate together for balance.
I guess the only way to check a pressure plate for balance is to mount it to the flywheel.
The machine shop said they could weld a weight on the pressure plate to balance it.
The service adviser told them not to touch it, because they needed it as proof so they could get reimbursed for their labor.

When I picked up the truck, I told them that if the rear main bearing seal starts
to leak or if a tranny bearing starts making noise, I'll be back.

Lesson learned:
It might be a good idea to check if the flywheel, pressure plate and clutch all mounted together, are balanced before installation.
I'm not sure if you can balance, with the clutch disc sandwiched between the flywheel & pressure plate.

I don't know about the disc, but most shops that do balancing can balance the flywheel and pressure plate together.

Thanks for the information. I hope they are relatively balanced as I plan to bolt it all back up today. It has been raining here for the last 10 or so days, but beautiful sunny driving weather is coming.

Just a thought...if the flywheel and pressure plate are not balanced well, couldn't the pressure plate be rotated to mount in a different location while assembled?

Wish me luck.

Paul

The most common procedure for balancing a diaphragm spring pressure plate is to weld a short piece of round stock to the cover, sort of like a wheel weight. The Borg & Beck style pressure plate has a series of holes drilled in the cover, and a slug of Mallory metal (heavier than lead) is tapped into one of more of the holes for balancing purposes. Spinning the flywheel and clutch cover is a good idea- - -including the disc isn't, because there's no way to predict where it will lock up when the clutch is engaged because it's splined to the transmission input shaft.
Jerry

Got it all put back together today. It was raining today so my test drive was not on maintained highway. Revving the engine in neutral does not reveal any vibrations, it is actually much better than it was before. The clutch functions great, and getting a good free play adjustment was easy with the new combination of parts. I am anxious to double clutch with a non-synchronized transmission that does not have a dragging clutch disk. I suspect I may see a boost in my proficiency.

Waiting for a sunny day.

Thanks guys, I appreciate the coaching.

Paul

That is very good to hear Paul!