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I have a little bit of chatter in the clutch when I idle in neutral on my 1970 LS-5. The chatter goes away when I press the clutch petal. How do I know when the clutch is ready to be replaced? What other parts are involved in this job and what is a reasonable cost (parts/labor)? Are these parts all available from GM? Anyone have any experience with other suppliers?
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Tony -
Re: Clutch Replacement on LS-5
Tony----
It's hard to say what the chatter is, but a failing clutch wouldn't cause that type of problem. It may be a failing clutch release bearing or it may be an improperly adjusted clutch. C3s clutches are an art to get properly adjusted. It's usually difficult or impossible to get the amount of free play specified in the service manual without also causing incomplete release when the pedal is fully depressed. I usually try to adjust it so that I have "some" free play and complete disengagement with the clutch pedal fully depressed. When you cannot prevent the clutch from slipping after adjusting it properly signals the time for clutch replacement.
All of the necessary parts are still available from GM. Clutch cover with pressure plate is GM # 3884598. Clutch disc is GM # 10148045. Clutch release bearing is GM # 908244. These are usually the only parts you need to replace. However, if you need them the flywheel is GM #3993827 and the release fork is GM # 3887177.
Centerforce makes a good hi-performance replacement clutch, but I still prefer the GM set-up.In Appreciation of John Hinckley -
Re: Clutch Replacement on LS-5
Tony----
It's hard to say what the chatter is, but a failing clutch wouldn't cause that type of problem. It may be a failing clutch release bearing or it may be an improperly adjusted clutch. C3s clutches are an art to get properly adjusted. It's usually difficult or impossible to get the amount of free play specified in the service manual without also causing incomplete release when the pedal is fully depressed. I usually try to adjust it so that I have "some" free play and complete disengagement with the clutch pedal fully depressed. When you cannot prevent the clutch from slipping after adjusting it properly signals the time for clutch replacement.
All of the necessary parts are still available from GM. Clutch cover with pressure plate is GM # 3884598. Clutch disc is GM # 10148045. Clutch release bearing is GM # 908244. These are usually the only parts you need to replace. However, if you need them the flywheel is GM #3993827 and the release fork is GM # 3887177.
Centerforce makes a good hi-performance replacement clutch, but I still prefer the GM set-up.In Appreciation of John HinckleyComment
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Re: Clutch Replacement on LS-5
Tony, based or your description of the problem, I agree with Joe, it doesn't sound like the clutch itself. Have you checked the linkage rods to the clutch for wera and do rou have the anti-rattle springs installed? These can cause some intresting noises.Comment
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Re: Clutch Replacement on LS-5
Tony, based or your description of the problem, I agree with Joe, it doesn't sound like the clutch itself. Have you checked the linkage rods to the clutch for wera and do rou have the anti-rattle springs installed? These can cause some intresting noises.Comment
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Multiple Choice
Your throw-out bearing may still be in motion under a very light load from the fork even with your foot off the pedal. Sometimes old bearings make a slight scraping sound until they are fully loaded when you depress the pedal.
I've installed a variety of "street" clutches in Corvettes with mixed results. Here are my opinions. Sheiffer, Zoom, Weber, and Hays: too much pedal pressure for my taste, smooth engagement, strong holding, moderate cost. GM stock: light pedal pressure, smooth engagement, acceptable holding, very high cost. New stock aftermarket (Carquest, probably Luk): moderate pedal pressure, smooth engagement, acceptable holding, moderate cost. Centerforce: moderate pedal, smooth engagement, strong holding, high cost. Aftermarket rebuilt: high pedal pressure, possible chatter during engagement, acceptable holding, low cost.
I always resurface and balance the flywheel. I also suggest that you install a new pilot shaft bushing in the crankshaft. The GM bushing is now actually a little bearing, but real bushings are still available from the aftermarket. GM sells a quality pilot bearing, but your bellhousing must be perfectly aligned for a bearing to live as long as a bushing.Comment
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Multiple Choice
Your throw-out bearing may still be in motion under a very light load from the fork even with your foot off the pedal. Sometimes old bearings make a slight scraping sound until they are fully loaded when you depress the pedal.
I've installed a variety of "street" clutches in Corvettes with mixed results. Here are my opinions. Sheiffer, Zoom, Weber, and Hays: too much pedal pressure for my taste, smooth engagement, strong holding, moderate cost. GM stock: light pedal pressure, smooth engagement, acceptable holding, very high cost. New stock aftermarket (Carquest, probably Luk): moderate pedal pressure, smooth engagement, acceptable holding, moderate cost. Centerforce: moderate pedal, smooth engagement, strong holding, high cost. Aftermarket rebuilt: high pedal pressure, possible chatter during engagement, acceptable holding, low cost.
I always resurface and balance the flywheel. I also suggest that you install a new pilot shaft bushing in the crankshaft. The GM bushing is now actually a little bearing, but real bushings are still available from the aftermarket. GM sells a quality pilot bearing, but your bellhousing must be perfectly aligned for a bearing to live as long as a bushing.Comment
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Re: Clutch Replacement on LS-5
HI,
I too have 1970 LS5 and I just went through this a 2-3 weeks ago. I got quotes from three different shops. The complete job included clutch, pressure plate, bearing, and fly wheel re-surface. Quotes were from $650- to $785.00. That is alot of money to me. Thats where this site has been great, I asked for the step by step proceedure and Joe Lucia posted great instructions. It took less than 7 hours, and that included time to take the fly wheel to the machinist to be re-surfaced. The clutch kit was $175.00 and the machine work was 18.00. With the money we saved I bought a new exhaust from Corvette Central.
This is what JOE LUCIA sent me, so all the credit goes to him.
1)Remove driveshaft 2)Remove shifter linkage, including shifter rods attached to the transmission and remove complete shifter unit from the car 3)Unbolt and remove rear transmission mount and exhaust bracket 4)Remove speedometer cable at transmission 5)Remove transmission lock cable(which connects to bracket on steering column). 6)Remove 4 bolts retaining transmission to bellhousing 7)Pull transmission back until input shaft clears bellhousing; then drop nose and lower to floor. 8)Disconnect clutch linkage at clutch fork 9)Remove bellhousing to block retaining bolts 10)Remove bellhousing 11)Remove clutch pressure plate assembly by removing 6 bolts retaining it to flywheel. 12)Remove clutch release bearing from clutch fork 13)Install new clutch release bearing on fork; carefully pack the inner, annular groove in the bearing(between bearing and transmission bearing retainer) with hi-temp grease. Lightly grease the outer groove where bearing attaches to fork. 14)Check flywheel surface for heat cracking or uneven surface or excessive heat marking(bluing). Resurface or, preferably, replace if necessary. If replacing or removing flywheel, I recommend replacingflywheel bolts with new ARP flywheel bolts. 15)Install new pressure plate and clutch disc assembly. Use pilot shaft to retain and center the disc. I recommend an old transmission input shaft of 10 spline 1-1/8" size(like your transmission input should be if your trans is original). These work better than plastic or wooden pilot shafts available in auto parts stores. 16)Torque pressure plate bolts to specifications; I recommend using new ARP pressure plate bolts. 17)Reverse all other procedures to re-install. 18)Adjust clutch per service or AIM instructions.
Mark#32244Comment
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Re: Clutch Replacement on LS-5
HI,
I too have 1970 LS5 and I just went through this a 2-3 weeks ago. I got quotes from three different shops. The complete job included clutch, pressure plate, bearing, and fly wheel re-surface. Quotes were from $650- to $785.00. That is alot of money to me. Thats where this site has been great, I asked for the step by step proceedure and Joe Lucia posted great instructions. It took less than 7 hours, and that included time to take the fly wheel to the machinist to be re-surfaced. The clutch kit was $175.00 and the machine work was 18.00. With the money we saved I bought a new exhaust from Corvette Central.
This is what JOE LUCIA sent me, so all the credit goes to him.
1)Remove driveshaft 2)Remove shifter linkage, including shifter rods attached to the transmission and remove complete shifter unit from the car 3)Unbolt and remove rear transmission mount and exhaust bracket 4)Remove speedometer cable at transmission 5)Remove transmission lock cable(which connects to bracket on steering column). 6)Remove 4 bolts retaining transmission to bellhousing 7)Pull transmission back until input shaft clears bellhousing; then drop nose and lower to floor. 8)Disconnect clutch linkage at clutch fork 9)Remove bellhousing to block retaining bolts 10)Remove bellhousing 11)Remove clutch pressure plate assembly by removing 6 bolts retaining it to flywheel. 12)Remove clutch release bearing from clutch fork 13)Install new clutch release bearing on fork; carefully pack the inner, annular groove in the bearing(between bearing and transmission bearing retainer) with hi-temp grease. Lightly grease the outer groove where bearing attaches to fork. 14)Check flywheel surface for heat cracking or uneven surface or excessive heat marking(bluing). Resurface or, preferably, replace if necessary. If replacing or removing flywheel, I recommend replacingflywheel bolts with new ARP flywheel bolts. 15)Install new pressure plate and clutch disc assembly. Use pilot shaft to retain and center the disc. I recommend an old transmission input shaft of 10 spline 1-1/8" size(like your transmission input should be if your trans is original). These work better than plastic or wooden pilot shafts available in auto parts stores. 16)Torque pressure plate bolts to specifications; I recommend using new ARP pressure plate bolts. 17)Reverse all other procedures to re-install. 18)Adjust clutch per service or AIM instructions.
Mark#32244Comment
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