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Old 02-09-2006, 02:00 PM   #1
brucep
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Default Why does my clutch shutter during low rpm launces?

The car is a 66 with L-79 and M21.

The clutch operation used to be perfectly smooth during low rpm takeoffs in 1st gear. Now there is a bit of a shutter if I let the clutch out slowly during low rpm starts (at or below 1500 rpms). Before I noticed this shutter I had dragged the clutch a bit while moving slowly up a steep grassy incline on a hot day behind a row of slow moving cars. After, I got out of the car and could smell something. I assumed I had overheated the clutch disk.

Would this cause my shutter? But whatever caused it, what options do I have for getting the clutch back to smooth engagements at low rpms? The clutch has about 5K miles on it, and I never abuse it (but for this one incident).

Thanks
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Old 02-09-2006, 03:34 PM   #2
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So you supported the weight of the car on the hill with the clutch partially engaged? How long? My guess is that the clutch and flywheel overheated and now the surface is glazed over and blue and possibly the flywheel has heat cracks.

Clutches are unforgiving items. When they get damaged or go bad, there is little you can do to repair. If the shudder is too bad, you're going to have to replace the clutch and most likely resurface the flywheel.


probably looks like this:
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Old 02-09-2006, 04:37 PM   #3
brucep
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Default say it aint so.

Nice(?) picture brian.
How long did I ride the clutch you ask? I'd say I was off and on the brake and clutch for a total of about a minute. I never would have thought anything of it if it weren't for the burn smell afterwards.

Last edited by brucep; 02-09-2006 at 04:39 PM.
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Old 02-09-2006, 06:19 PM   #4
GCD1962
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There are other things also that can create the chattering. Loose (or broken) spring in the clutch disk. Weak or broken spring in the clutch plate. Improper balance between the springs for the fingers on the clutch. All require the removal of the clutch & disk. I've always found that once you have it apart replace the clutch plate, disk, bearing and check flywheel for cracks or run out
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Old 02-09-2006, 06:42 PM   #5
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If for only a minute or so I would doubt extensive damage, but I don't know how you normally launch the car. Try a few "hard" launches on the clutch, it might help (and certainly won't hurt it any more than it is already)...
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Old 02-09-2006, 06:53 PM   #6
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I'm getting my car back tomorrow after, among other items, a new clutch and flywheel. My clutch would chatter so badly once in a while it would shake the car. My flywheel had heat spots badly in it, the part that depresses the throwout bearing had a piece missing off it, and the plates were glazed. It was the original clutch, 58K miles on it. To launch the car smoothly I also had to raise the rpms and as I let the clutch out gently feed more power.

I'm just glad I caught it before it let go completely.

Also went with a new HI PO lightweight flywheel.

If this keeps up I'll have a 2006/65' Vette.

Since I'm also into offshore boats I have come to the conclusion if it's fiberglass, it's expensive. This morning a buddy suggested my vanity plate should read: BOAT #2
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Old 02-09-2006, 07:51 PM   #7
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Quote:
Originally Posted by Denney
If for only a minute or so I would doubt extensive damage, but I don't know how you normally launch the car. Try a few "hard" launches on the clutch, it might help (and certainly won't hurt it any more than it is already)...



This has worked for me in the past. You might get lucky. If you just caught a faint smell of the clutch, I doubt you hurt it. If the odor lingered on, you may have.
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Old 02-09-2006, 09:48 PM   #8
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I've completely toasted a clutch four times while launching the car hard. Had to get it towed all four times.

Twice in a 68' 383 Barracuda

Once in a 70 Ram Air IV GTO

Once in a V-6 Capri don't remember the year (girlfriend's car, she was REAL happy), she'd just gotten it back that same day after replacing the tranny.....
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Old 02-09-2006, 09:48 PM   #9
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I agree with Denney and MikeM. I had a lot of clutch chatter at take off and was just living with it until this past fall at the Pure Stock (?) Muscle Car Drag Event I participate in.

When you're launching hard, say 1,500 to 1,800 R's, I would get a lot of tire spin but I ran my '5 about 9 times in drag race events and, guess what, no more chatter. She drives out nice and easy with very little loud pedal help. It did work for me.

Try it!

Regards,

Jim
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Old 02-09-2006, 10:10 PM   #10
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My racing technique may be off, but for me, when I "hard launch" I rev the motor in my 65 to 4500-5000 RPM, and let the clutch out slow enough so that when it is fully "Out" the RPM is 4000-4500. Not a daily deal, but for the strip, it works great. With 4:11's or the 5:13's I had in my chevelle it was a matter of seconds we are talking about.

My last clutch failure was racing a 69 Z28 camaro. Shifting from 2nd to 3rd I bent the fingers on the clutch and pushed the T-O bearing through them. Clutch pedal stayed on the floor, and it made a lot of noise.

I never had a chatter as you describe.

As mentioned, if you go to the trouble to get the clutch out, replace it, and resurface the flywheel.

The funky smell is the same as hot brakes. If you have ever driven over the road trucks, or follow behind them in the mountains, you have smelled the infamous brake/clutch smell.

I have only smelled that once in my vette, and it was from my buddy driving it home from the bar, while I was in the car. He launched in 3rd and in an attempt to keep the car rolling, he just road the clutch and mashed the gas.

Mark
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Old 02-09-2006, 10:22 PM   #11
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Hey ghostrider,

How ya' be? How's the rebuild progressing on your '5?

Ya' know, you young whipper snapper's always did have a hotter foot at those drag events. I just didn't want to go up in smoke which I usually do on that last yellow...just standin' around burnin' rubber. 4,500 - 5,000 r launches! HOLY MACKERAL! That would surely cure a clutch chatter!

Jim
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Old 02-09-2006, 10:34 PM   #12
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Doing good !

The rebuild is in the parts collecting period.

I got the motor out a few weeks ago, and last week brought it over the builder.

As of now, going with
Lt-1 Cam
L-88 Flywheel (15lbs.)
Crower Rods
585 lifters (maybe the last set on planet earth)
New LUK Clutch

I spent most of the cold ice laden month of Jan blasting and painting parts. Everything that came off was cleaned, blasted and painted.

Took my driveshaft over to the driveline services and they balanced it at 4500 RPM, and said it had some run out, so hopefully that will address the high MPH vibration.

The car is going up to my buddies alignment/frame shop sometime this month for a complete front end re-build. New A-arm bushings, ball joints etc. With the motor out, why not?

My hood is going to the body shop this week to get the frame "gum dropped" back on. It is loose in all but a few spots.

Mark
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Old 02-09-2006, 11:22 PM   #13
78Vette-SA
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First shutter then eventual big bang!

I would surface the flywheel and throw a new clutch in it. But that's me.

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Old 02-09-2006, 11:36 PM   #14
brucep
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So one school of thought is get rough with it and that will smooth it out, the other is replace it before it totally comes apart?

Last edited by brucep; 02-10-2006 at 07:53 AM.
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Old 02-10-2006, 09:05 AM   #15
GCD1962
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re-read my post about the springs in the clutch. Improper pressure has more to do with chatter than anything else. It was a very common problem also for cars with closed driveshafts.
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Old 02-10-2006, 09:27 AM   #16
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Quote:
Originally Posted by 78Vette-SA
First shutter then eventual big bang!

I would surface the flywheel and throw a new clutch in it. But that's me.

Click the image to open in full size.
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EXACTLY the reason I replaced my whole clutch and flywhee. Have heard the "big bang" before and don't want to hear it again.
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Old 02-10-2006, 12:03 PM   #17
brucep
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Quote:
Originally Posted by GCD1962
re-read my post about the springs in the clutch. Improper pressure has more to do with chatter than anything else. It was a very common problem also for cars with closed driveshafts.

I get shutter, but no chatter (vibration without noise).
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Old 02-10-2006, 07:24 PM   #18
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Clutch chatter (not noise, but vibration on engagement) has many posssible causes, glazed flywheel, warped flywheel or pressure plate, broken motor or transmission mount, worn clutch fork or front bearing retainer, clutch disc defects, severly off center bellhousing to engine alighnment (not likely with stock GM), worn linkage parts. About the only way to be sure to fix it is to tear it down and replace any parts with any wear, surface flywheel and pressure plate, and clean everything.
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Old 02-10-2006, 07:25 PM   #19
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repeat

Last edited by DansYellow66; 02-11-2006 at 07:44 AM.
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Old 02-10-2006, 07:31 PM   #20
Formula Outlaw
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Got the car back today. Man, what a difference, wouldn't know it was the same car. Replaced everything including flywheel.

Now I just need to learn to drive it again.....
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Old 02-10-2006, 07:31 PM
 
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