T56 shifting issue
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Joined: Nov 2007
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From: Woodstock GA
T56 shifting issue
This tranmission is not in my C3, its in my 97 Camaro SS, but I'm hoping someone here will have some ideas. For a little background, the car had a fairly new clutch and the slave was replaced within the last 20k miles. I was driving on the interstate, and it wouldn't downshift out of 6th...well, I eventually got it into 2nd, and got off the road. Before this, it shifted fine...no noise, no jumping out of gear, no hydraulic issues. I limped it how, took it apart, and didn't really see anything wrong. The hydraulics looked ok. Since I had it apart, and had a new McLeod disk and pressure plate, I put them in. No change. Someone on another forum suggested that a pin may have come loose inside the transmission (it had happened to the guy replying), but that doesn'tmake sense to me since I can shift into any gear, as long as the engine isn't running. Any ideas? I have a T56 rebuild manual and will tear into this thing if I have to, but I'm thinking maybe it is the hydraulics...even though they aren't leaking, and the fluid level is adequate. Could it by bypassing internally and not building pressure?
Racer
Joined: May 2007
Posts: 296
Likes: 4
From: London Ontario
Sounds like the clutch isn't disengaging to me, which would lead me to believe it is a hydraulic problem. Does the clutch feel spongey, It could have got air in it and not be disengaging all the way. I am no expert but that would be my best guess. It never hurts to bleed the system if you have the time and tools
Drifting
Joined: Sep 2004
Posts: 1,625
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From: Miami FL
Try contacting Amber @ SixSpeed, Inc. Everybody swears by them on the LS1tech forum and other forums. I will be ordering my Viper T56 for my 69 vette from them today.
http://0174de9.netsolstores.com/
http://0174de9.netsolstores.com/
Thread Starter
Pro
Joined: Nov 2007
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From: Woodstock GA
Sounds like the clutch isn't disengaging to me, which would lead me to believe it is a hydraulic problem. Does the clutch feel spongey, It could have got air in it and not be disengaging all the way. I am no expert but that would be my best guess. It never hurts to bleed the system if you have the time and tools
Thread Starter
Pro
Joined: Nov 2007
Posts: 741
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From: Woodstock GA
Try contacting Amber @ SixSpeed, Inc. Everybody swears by them on the LS1tech forum and other forums. I will be ordering my Viper T56 for my 69 vette from them today.
http://0174de9.netsolstores.com/
http://0174de9.netsolstores.com/
Team Owner
Joined: Oct 2004
Posts: 23,831
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From: Springfield MO
St. Jude Donor '07
What baffles me is, how does it go from no clutch issue at all to suddenly no clutch, while crusing at 2000 rpm? Thats what has me. The car is at my parents house (it was closer than going home), so I can't run out and check, but I have never had to bleed an LT1 clutch. Just dumped in some fluid, pump it a couple of times, and its good. I'll be able to check sometime this week, just to be sure.
Drifting
Joined: Sep 2006
Posts: 1,259
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From: MS
The pickups with the ZF 6-speeds would also lose the clutch after extended highway driving, and this was do to excessive heat boiling the fluid in the clutch master cylinder. Not sure what the problem is, but something to consider. Can't remember the exact procedure, but Chevy had a test to diagnose a clutch that was not fully disengaging. Let it idle in neutral for a minute or two or after you have been driving it and it's hot, then push in the clutch, wait I think 3 or 4 seconds and then go straight to reverse. If it grinds, the clutch is not disengaging properly. Somebody might correct the number of seconds you are supposed to wait, maybe it's a little longer.
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Thread Starter
Pro
Joined: Nov 2007
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From: Woodstock GA
The pickups with the ZF 6-speeds would also lose the clutch after extended highway driving, and this was do to excessive heat boiling the fluid in the clutch master cylinder. Not sure what the problem is, but something to consider. Can't remember the exact procedure, but Chevy had a test to diagnose a clutch that was not fully disengaging. Let it idle in neutral for a minute or two or after you have been driving it and it's hot, then push in the clutch, wait I think 3 or 4 seconds and then go straight to reverse. If it grinds, the clutch is not disengaging properly. Somebody might correct the number of seconds you are supposed to wait, maybe it's a little longer.
Intermediate
Joined: Nov 2007
Posts: 45
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From: Lincoln NE
I agree I think it sounds like a key in one of the synchronizers.
I have a T56 in my Corvette and just had the same thing happen to me. Just one day got stuck in 4th gear. Drove it a couple of more times after that with no problem, them boom, stuck in third gear.
Got the tranny out, it was the pins in the 3rd / 4th synchro.
I bet that is your problem except with 5th / 6th synchro.
I have a T56 in my Corvette and just had the same thing happen to me. Just one day got stuck in 4th gear. Drove it a couple of more times after that with no problem, them boom, stuck in third gear.
Got the tranny out, it was the pins in the 3rd / 4th synchro.
I bet that is your problem except with 5th / 6th synchro.
Last edited by dahctor; Apr 16, 2008 at 08:06 PM.
Melting Slicks
Joined: Sep 2004
Posts: 2,412
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Hold on the clutch pedal with the car stopped and the engine idling with the windows down, then drop it suddenly (in neutral) you should be able to hear it smack against the flywheel. I have a T56 in my C3 and I can hear it drop. If you don't hear anything I would suspect the hydraulics, check for fluid leaks and check the fluid level.
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From: Woodstock GA
I agree I think it sounds like a pin in one of the synchronizers.
I have a T56 in my Corvette and just had the same thing happen to me. Just one day got stuck in 4th gear. Drove it a couple of more times after that with no problem, them boom, stuck in third gear.
Got the tranny out, it was the pins in the 3rd / 4th synchro.
I bet that is your problem except with 5th / 6th synchro.
I have a T56 in my Corvette and just had the same thing happen to me. Just one day got stuck in 4th gear. Drove it a couple of more times after that with no problem, them boom, stuck in third gear.
Got the tranny out, it was the pins in the 3rd / 4th synchro.
I bet that is your problem except with 5th / 6th synchro.
Last edited by 1981Z06Vette; Apr 16, 2008 at 04:54 AM.
Thread Starter
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Joined: Nov 2007
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From: Woodstock GA
Hold on the clutch pedal with the car stopped and the engine idling with the windows down, then drop it suddenly (in neutral) you should be able to hear it smack against the flywheel. I have a T56 in my C3 and I can hear it drop. If you don't hear anything I would suspect the hydraulics, check for fluid leaks and check the fluid level.
Melting Slicks
Joined: Sep 2004
Posts: 2,412
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My blower whine is deafening at idle, I have big heads and a big cam aswell. And I have long tube headers flowing into dual 3" mandrel bent pipes quieted only by straight through Dynomax bullet mufflers. But I can still hear the clutch smack.
Intermediate
Joined: Nov 2007
Posts: 45
Likes: 0
From: Lincoln NE
Did you try to turn on the car and put it in reverse (if it grinds it is clutch disengagement)? With nothing in front of you car...can you start it in gear, or does it try to jump?
If no on both of those, then it is a synchro.
It is hard to fix, you need specialty tools and some know how. With the right tools and the right instructions anything is easy though. There is a ton of information on the internet about the transmission.
Last edited by dahctor; Apr 16, 2008 at 08:06 PM.
Team Owner
Joined: Jan 2006
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From: Crossville TN
If there are "shear pins" in that unit, and they have sheared, you're putting too much torque through the unit for it to survive. That's the purpose of a shear-pin in a tranny box....to keep it from turning to junk when you overload it.
Intermediate
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From: Lincoln NE
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From: Woodstock GA
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