C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

clutch bleeding revisited

Old 05-09-2003, 08:27 AM
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Jim85IROC
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Default clutch bleeding revisited

I've had the new master & slave in the car for a few hundred miles, and I swear the shifting is getting worse every day. I've bled and bled and bled and haven't seen an air bubble since right in the beginning. It also seems to feel like my clutch is fully disengaging. When stopped, I can drop it into 1st or reverse all day long with absolutely no difficulty. My difficulty comes when I drive. Sometimes the 1-2 grinds a little bit. Downshifts are a nightmare all together. Downshifting into 4th or 3rd is smooth as silk sometimes (especially if I heel & toe to match the rpms), and other times it won't let me in no matter how many times I double clutch unless I really force it. Downshifting into 2nd is a gear-grinding fiasco unless I'm going under 15 and I do it very slowly. Downshifting into 1st at anything over 5mph grinds and won't engage.

The transmission wasn't behaving too well before the master/slave swap, but it wasn't this bad. Of course, right after the swap it wasn't this bad either. It's like it gets worse daily.

Do I just keep bleeding until the end of time dispite the fact that it seems like the clutch is fully disengaging, or can I just chalk this up to the transmission? A rebuild is in my very near future, but I want to make damn sure my hydraulics don't kill the new one.


[Modified by Jim85IROC, 8:27 AM 5/9/2003]
Old 05-09-2003, 09:21 AM
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Atok
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Default Re: clutch bleeding revisited (Jim85IROC)

Have you checked the fuild level in the transmission lately? That might be your problem. If it's not fluid level it sounds like the sychros in your tranny are worn out. :(
Old 05-09-2003, 10:29 AM
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Jim85IROC
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Default Re: clutch bleeding revisited (Atok)

My 17mm allen socket just came in, and I've got 3 quarts of castrol sitting on the work bench. That's today's project. But... if it's low on fluid, chances are the damage has already been done. I just want to feel confident that my hydraulics are sound so I don't ruin a very expensive rebuild.
Old 05-09-2003, 10:42 AM
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HammerDown
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Default Re: clutch bleeding revisited (Jim85IROC)

Sounds to me like your hydraulic system is ok. I mean, if there is no air in the system, and the clutch is fully disengaging, that's all there is to it. I think you're either low on fluid, or the syncros are bad due to some problem that was present before you bought the car. Either way, I really hope you can get this worked out. When your car gives you this much trouble on a regular basis, it's hard not to look at it with anything but frustration. Just stay on it, you'll figure something out. :cheers:
Old 05-09-2003, 11:30 AM
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frank moran
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Default Re: clutch bleeding revisited (Jim85IROC)

I have a similar problem, mine grinds going just into 2nd, especially when in OD. If its not in OD its ok but still have to be careful I have a trans kit for it so as soon as i get rid of an 84 in my garage I'm going to get into the gear box, I suspect synchros...but i would sure like to see it be air in th system, I'll try bleeding with a mitivac from the bottom up.
Old 05-09-2003, 12:44 PM
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Aaron71771
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Default Re: clutch bleeding revisited (Jim85IROC)

Jim, I would say if you have smooth shifting (1st to reverse) after first starting the car in the morning and not pumping the clutch at all (brake on), then your hydralics are working fine. When you pull the trans, it wont be that hard to check the cluch system out.

My car will actually try to move when I shift, and after being put in gear it tries to move some. I have a heck of a time shifting between first and reverse. I am pretty sure this is what a non-fully releasing clutch feels like. My cluthc fork is so far into the bell housing (don't know why yet)I get maybe 1/4" to 1/2" of total slave rod movement.
Old 05-09-2003, 01:48 PM
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Jim85IROC
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Default Re: clutch bleeding revisited (Aaron71771)

Aaron, your problem is without a doubt that the clutch isn't fully releasing.

I think you read one of my other threads where I described how I bench bled my master cylinder. That was super easy, and seems to have worked perfectly. I would definately say that you should try it. You can get a vacuum gun like mine from Eastwood for about $35.
Old 05-09-2003, 02:13 PM
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Aaron71771
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Default Re: clutch bleeding revisited (Jim85IROC)

Jim,

My clutch is fully bleed now, there is zero air in it. My problem now is something to do with where my clutch fork is, not sure what until I pull it apart :(
Old 05-09-2003, 05:26 PM
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Davemc1963-87conv
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Default Re: clutch bleeding revisited (Jim85IROC)

Jim, make sure you are using a GL5 gear oil and not a GL4. (I inadvertantly tried Redline MTL once which is a GL4 not GL5 and the shift quality was terrible, I soon flushed it out and used a fully Synthetic GL5. I have made an assumption you have a 4+3, if its a ZF all this is totally irrelevant to you. However if you need a lot of force to shift gears with a 4+3, GM recommends you add up to two bottles of 'positraction' gear additive. Boy does this make a difference together with fully synthetic 75/90. As an aside, if you use heavier oil such as a straight 90w or heavier gear oil, your gear shifting will be difficult when cold.
As for bleeding. In the UK, we have a product called 'Easybleed' manufactured by a company called Gunsons I believe it may be marketed by a division of Actron in the US. I may have also seen it in a JC Whitney catalogue as well, but can't be sure. It is a reservoir bottle that screws on to the master cylinder and pressure bleeds the system by using the presure from a car tyre. The clutch master cylinder on my 87 is a Girling unit and the Easybleed has an adapter/top specifically to fit it. It works a treat and is about £25 over here.
Hope this is of some help :steering:
Old 05-10-2003, 08:57 AM
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Atok
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Default Re: clutch bleeding revisited (Jim85IROC)

What method do you use to bleed your clutch system? I've seen numerous different opinions on how it should be done but none that match the GM recommended procedure. When I replaced my cylinders I just followed the procedure in the GM Service Manual, works like a charm. The "meat" of the procedure is to remove the slave cylinder from the clutch housing, hold the slave so the bleed screw is pointing straight up, have someone press and hold the clutch pedal, open the bleed screw. While holding the pedal, close the bleed screw. Repeat until no more air. Worked A1 for me. I had the tranmission out of the car at the time (changing clutch) and verified the clutch was releasing fully so I know this procedure works.

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