A recent intermittent problem on my 63 is occuring. When going into 1st gear from reverse I am getting a grinding sound and vibration with the clutch depressed. It stops when the clutch is released, it also happens occasoinally when reverse is selected and the clutch is depressed. Shifter is original with 100k plus on it, tranney rebult 3000 miles ago by local shop used by ncrs members, clutch , fly wheel and throw out bearing replaced with tranney( Centerforce). In all other ways it is fine,no problems once moving or up shifting. Could the shifter be worn out ? Is it not coming out of reverse fully? Any help would be appreciated!
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Re: 63 Muncie 4 spd
James-----
I'd say that your clutch needs to be adjusted. On a Corvette, clutch adjustment can be tricky. Often times, when you have the specified amount of free-play, you will also have incomplete disengagement at full deflection. You MUST have some free-play, but you may have to settle for less than the GM spec.In Appreciation of John Hinckley -
Re: 63 Muncie 4 spd
There have been some recent threads over on the C1 & C2 Corvette Forum on Centerforce clutches. Based on what I've read these clutches don't appear to be engineered to OEM dimensions, so they often don't release properly with the OEM clutch linkage, or you can't obtain proper freeplay.
You might want to go over to the Corvette Forum (C1 $ C2 discussion) and page "ghostrider20". I think Mark ended up removing the Centerforce and replacing it with an OEM replacement clutch from Sachs, Luk, or Borg-Warner.
I've always had very good service from OEM clutch components and the OEM replacement components from these vendors are engineered to OEM specs. Unless your drag racing, you don't need an aftermarket clutch. Like most aftermarket equipment, I think they're way overhyped.
DukeComment
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Re: 63 Muncie 4 spd
Duke----
Yes, I agree. The "adjustment problem" is the primary reason that I use and recommend GM clutches. For a 63-81 Corvette, even when a GM clutch is used the clutch adjustment is often "tricky". When other clutches are used, even a slight difference from OEM dimensional specs can make the adjusment virtually impossible. Since I ABSOLUTELY HATE to "go back in" to replace components that I can't get to work properly (and, especially, clutches) I forego the "performance improvement" that aftermarket clutches MAY provide and go with a "known quantity". GM clutches are great street clutches, too.
I realize that many folks have used and are extremely pleased with aftermarket clutches, especially Centerforce, but I, personally, would only go that route if a GM clutch was not available. And, for myself, I've seen to it that a 3X lifetime supply WILL BE AVAILABLE [none for sale].
As a matter of fact, virtually all the GM clutch components for 53-81 Corvettes are now discontinued. All of the 10.4" pressure plate assemblies and all of the friction disc for both 10.4" and 11" clutches are also now discontinued.In Appreciation of John HinckleyComment
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Re: 63 Muncie 4 spd
Now that most of the GM clutch components are discontinued, that leaves the aftermarket, which I subdivide into the "hot rod replacment market" such as Centerforce, and the OEM replacment market such as Luk, Sachs, and Borg-Warner.
Since I've never heard any complaints about fit or performance on the OEM replacment clutches, my personal choice and recommendation to others would be to opt for the Luk, Sachs, or Borg-Warner when the time arrives for a new clutch.
DukeComment
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Re: 63 Muncie 4 spd
James:
I installed a standard (do NOT specify heavy duty, unless your left calf and quadracep are used to a severe workout) Borg Warner clutch unit in my 1965 327/365. In my opinion (and a few powershifts @ 6000RPM), this unit can more than handle whatever you can throw at it in normal and/or very spirited street use.
Make sure your pivot ball stud in the bellhousing is correct for your application (Joe L. should be able to help you out with p.n.'s) as this could be the root of your problem. If all linkages are proper, then setting your free play to spec should not cause any problems.
JoeComment
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Re: 63 Muncie 4 spd
Thanks all for the replies. It seems the vote is that the Centerforce clutch maybe the problem. Just a point of clarification before I start replacing the clutch..it has operated very satisfactorily for at least 3000 miles with no adjustment problems etc. so I,m assuming this problem wouldn't necessarily start at the initial installation . Are there any adjustments that could be off I should check, aside from the clutch play, like the shifter linkages etc.that could cause these symptoms before I begin removing the tranney? ThanksComment
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Re: 63 Muncie 4 spd
I reviewed you original post and the symptoms are not completely clear to me, so let me give you some background and maybe some tests you can accomplish.
First, reverse is an old fashioned non-synchronized sliding gear. While in neutral with the clutch out, the clutchgear/countershaft and reverse idler is spinning. When you push in the clutch and immediately engage reverse, you will get a grind. A way to overcome this is to depress the clutch and wait a few seconds for the clutch gear/countershaft to spin down before engaging reverse. Another way is to first engage first gear, or any other forward gear. The resulting forward gear synchronizer action will stop the countershaft and allow reverse engagement without clash. This procedure is known as "clearing the gears" and is a good practice for skilled manual transmission drivers. I learned this when first exposed to typical three speed non-sychro first gear transmissions from the early prewar era. Prior to first gear engagement, it was SOP to "clear the gears" by depressing the clutch and engaging second gear, then first.
One summer while in college I drove GM Coaches on Alaska tours and they were equipped with four-speed "crash boxes" (non-sychronized), which required double clutching both up and down. Since there were no sychronized gears there was no effective way to clear the gears. The proper technique to engage first gear was to declutch and move the lever just to the point where I could feel the gears "kissing", then give the lever a quick jab to engage the gear. This way first gear could be engaged without clash. This technique is apparently lost to current coach chauffeurs, as everyone in recent memory just pushed the lever forward to the sound of gradually winding down clashing gears. Who the hell trains these people???!!!
A good way to check for clutch drag is to declutch in neutral and then just begin to engage reverse by moving the lever enough so you can just feel the gears begin to "kiss". You should feel the vibration frequency of the kissing gears decrease as the clutchgear/countershaft speed runs down. If the frequency remains constant and the clutchgear/countershaft does not run down, then the clutch is dragging. This can be corrected by DECREASING freeplay, however if decreasing freeplay does not eliminate the clutch drag at about a half inch or less of freeplay, then there is something amiss in the linkage or the clutch dimensions are too far from OEM spec to allow the clutch linkage to properly disengage the clutch.
In the forward gears, synchronizer action can overcome some clutch drag, but it will increase shift effort and synchronizer wear, so it's always a good idea to test for clutch drag using the reverse engagement test I outlined above anytime you check the clutch freeplay adjustment.
DukeComment
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Re: 63 Muncie 4 spd
james-----
If the clutch has performed satisfactorily for awhile, then I'd say that the clutch is not the source of your problem. The discussion regarding aftermarket-type clutches creating adjustment problems was, more-or-less, a general and follow-up discussion. As I mentioned from the start, I think that a clutch adjustment problem is at the root of yourr problem. Whether or not this is related to an aftermarket clutch installation is just a possibility. It could just be a plain old clutch adjustment problem.In Appreciation of John HinckleyComment
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Re: 63 Muncie 4 spd
Could your "problem" be attributed to good ole' "Lack Of Use"? If you only drive the car rarely and the car is stored in somewhat humid conditions, then you can suffer from the LOU syndrome... Does you problem "Clear up" after driving/shifting a number of times??? I have had a clutch actually "not release" when depressed after a period of LOU. (The car is stored in my basement garage) I attempted to start the car with the clutch depressed and in gear and the car "jumped". After the disc "freed" itself from the flywheel then everything was ok.... It definitely took me by surprise, (I thought I might have a collision with the wall) so now I always make sure I've got it in Neutral and the clutch disengaged before I attempt to start it after a long period of LOU.... Just some experiences
SteveComment
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Re: 63 Muncie 4 spd
I've always used Centerforce II's in my non-Corvette project cars, and they're outstanding (I've also fabricated the clutch linkage on those "from-scratch" cars to suit the application, and haven't had any free play-vs.-disengagement problems). I put a LuK "Vintage Replacement Line" diaphragm clutch in my '57 Corvette (from Paragon), and it operated perfectly and I had no linkage adjustment anomalies to deal with - all stock parts, no problems. LuK is the largest clutch manufacturer in the world - they are the OEM supplier of the 12" Viper clutch, which has proven to be far superior in service to any of the "tuner" clutches for the Viper.Comment
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