Manual Transmission T56 | T5 | MN12 | Clutches | Hydraulics | Shifters

Shifting problem persists...

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Old Aug 18, 2008 | 05:59 PM
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Default Shifting problem persists...

Can see an old thread regarding my problem here on ls1.com:
http://www.ls1.com/forums/forumdisplay.php?f=65

This morning while driving to a friends house I realized, if I shift hard/fast enough I go through this "notchy barrier", but a loud banging/grinding noise occurs. So, we decided to bleed my clutch after installing the new 02s and finally aligned the borla exhaust tips that we were planning on. My hydraulics did have air in it according to my friend which was doing the bleeding from underneath, but this did not help my notchy/grinding(when pushing it hard) shifting.

All this goes away if when I shift, I don't let go of the clutch and try to shift again. Example:

1) Press clutch down
2) Shift into any gear which is notchy/grinding if pushed hard and fast.(its as if a barrier is before the actual gear)
3) DO NOT RELEASE CLUTCH
4) Shift into any gear which is ultra smooth and brisk, almost as if the shifter just gets sucked into place... I ALWAYS WANT THIS FEELING!!!

The car is a '99 with 45k miles, stock shifter(but I doubt a shifter would magically get rid of a banging/grinding sound when shifting hard)
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Old Aug 19, 2008 | 04:57 PM
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Nobody has an idea?
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Old Aug 20, 2008 | 08:30 AM
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Do the clutch test to see if your clutch is fully disengaging:

Bring the car to a dead stop on a level surface with nothing in front of you. Push the clutch pedal to the floor and hold it there. Shift the car into first gear and leave the clutch pedal to the floor. Rev the car up to about 5500-6000 RPM or higher (where you shift) and see if the car starts creeping forward.

If the car starts moving at all, then your clutch is not fully disengaging at high RPM and you have an issue. Do this test once when you first start the car, once after some "spirited" driving for a few miles, then again when you're pulling the car in. Report back after that.
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Old Aug 20, 2008 | 09:22 PM
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Originally Posted by PewterScreaminMach
Do the clutch test to see if your clutch is fully disengaging:

Bring the car to a dead stop on a level surface with nothing in front of you. Push the clutch pedal to the floor and hold it there. Shift the car into first gear and leave the clutch pedal to the floor. Rev the car up to about 5500-6000 RPM or higher (where you shift) and see if the car starts creeping forward.

If the car starts moving at all, then your clutch is not fully disengaging at high RPM and you have an issue. Do this test once when you first start the car, once after some "spirited" driving for a few miles, then again when you're pulling the car in. Report back after that.
Didn't seem to have any movement at all and brought rpm to like 5.5-6k
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Old Aug 21, 2008 | 01:27 AM
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I experience something like that mostly in the lower rpm range if i try to jam it from first to second it feels like it hits a brick wall and then it gives if i keep applying pressure and goes into gear, it does not happen at higher rpms to me though. Also sometimes it will shift fine at all rpms out of nowhere.. so im going to bleed it again and again and see if it changes anything.

I have an ls7 clutch though.. not sure what yours is.
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Old Aug 21, 2008 | 07:20 PM
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One more thing that was happening when I was bleeding the clutch.
After I would pump and hold the clutch down for my friend to open up the bleeder valve. After he closed the bleeder valve and I let my foot off the clutch it wouldn't come back up. I would have to pull it back up with my hand or foot then sometimes pump it at least once and it would come up right away or a couple of times pushing/pulling the clutch for it to stay up again. This happened all the way through.

Would this mean anything?
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Old Aug 21, 2008 | 09:13 PM
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sounds like the same thing I am dealing with. I need a rebuild on my transmission ow because my syncros are hurt, the shift forks are probably bent, and the sliders may be broke as well.

I drove my car hard be4 I put in a strong clutch and it ended up hurting the transmission.
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Old Aug 21, 2008 | 09:23 PM
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Originally Posted by Tripintaz
sounds like the same thing I am dealing with. I need a rebuild on my transmission ow because my syncros are hurt, the shift forks are probably bent, and the sliders may be broke as well.

I drove my car hard be4 I put in a strong clutch and it ended up hurting the transmission.
Shouldn't that cause the problem to ALWAYS happen though? It seems if I depress the clutch and the shift its notchy, but if I shift again without letting go of the clutch its smooth as butter signifying(atleast to me) that something inside the tranny can't be really screwed up as it should always be notchy and not sometimes??
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Old Aug 22, 2008 | 11:05 AM
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If the pedal is remaining in the depressed position it is possible that you are having a hydraulic issue...most likely the slave cylinder. It seems like your issue is related to fluid transfer, meaning that the fluid once pushed to the slave is not returning up the line to the master when the pedal is released. This can be caused by air in the lines or by bleed-by where the fluid is passing the seals within the slave or master causing pressure to build behind the plunger that send it down to the slave.

The first thing I would do is try bleeding the hydraulics and see if there is any improvement in the pedal response. Also, check the fluid color as any discoloration can signal break-down and the need for a flush and refill. While you are at it, you can also have the hydraulic lines that route near the header wrapped with a heat resistant wrap to reduce the chances of boiling and thus aeration. I hope this info helps. Let me know if you need anything else. Thanks!
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Old Aug 22, 2008 | 06:08 PM
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Originally Posted by SPEC-01
If the pedal is remaining in the depressed position it is possible that you are having a hydraulic issue...most likely the slave cylinder. It seems like your issue is related to fluid transfer, meaning that the fluid once pushed to the slave is not returning up the line to the master when the pedal is released. This can be caused by air in the lines or by bleed-by where the fluid is passing the seals within the slave or master causing pressure to build behind the plunger that send it down to the slave.

The first thing I would do is try bleeding the hydraulics and see if there is any improvement in the pedal response. Also, check the fluid color as any discoloration can signal break-down and the need for a flush and refill. While you are at it, you can also have the hydraulic lines that route near the header wrapped with a heat resistant wrap to reduce the chances of boiling and thus aeration. I hope this info helps. Let me know if you need anything else. Thanks!
Ill try bleeding again, whats the best fluid to use? Any dot3/4?

Also, is there a quick/easy way to check the slave/master?
If not, whats the best way to check the slave/master and how would I go about doing this?

Thanks for the help so far!
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