T56 Issue? Please watch video
03-08-2011, 07:23 PM
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T56 Issue? Please watch video Is this normal? I've always had a knocking sound in my car when I go from accel to decel, or when it bucks in a parking lot, etc. I could never find it, but I think I may have just now.
The slip yolk piece rocks inside the transmission tailshaft, which is what that clunk sound is in the video. If you look closely you can see it moving. I think something needs to be replaced/fixed. What are your thoughts, is this normal? I know it looks like the U-joint is bad, but its solid.
Another thing to add, is my poly trans mount seems to be broken as well. The poly has de-laminated from the metal. Its all together, and looks normal, but you can feel what seems like metal on metal. Probably unrelated.
This setup is in a RX-7. The engine is mounted with poly mounts, and trans with poly mounts. The rear end is an IRS. The driveshaft angle was set to 1.5 deg.
http://www.youtube.com/watch?v=-FR0WgEti0Y
The slip yolk piece rocks inside the transmission tailshaft, which is what that clunk sound is in the video. If you look closely you can see it moving. I think something needs to be replaced/fixed. What are your thoughts, is this normal? I know it looks like the U-joint is bad, but its solid.
Another thing to add, is my poly trans mount seems to be broken as well. The poly has de-laminated from the metal. Its all together, and looks normal, but you can feel what seems like metal on metal. Probably unrelated.
This setup is in a RX-7. The engine is mounted with poly mounts, and trans with poly mounts. The rear end is an IRS. The driveshaft angle was set to 1.5 deg.
http://www.youtube.com/watch?v=-FR0WgEti0Y
Last edited by Kevin Doe; 03-08-2011 at 07:29 PM.
03-08-2011, 07:49 PM
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Just checked the 4 trannys on my floor with 2 shafts. Mine all do this and my turbo 400 does it more than the others.. No noises ever came from my cars like you are describing. I would start with replacing the mount. Then check your tq arm bushings and mounts. If you dont find anything there check out the rear end. Also go with 3 degrees on the shaft.
03-08-2011, 08:08 PM
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Just checked the 4 trannys on my floor with 2 shafts. Mine all do this and my turbo 400 does it more than the others.. No noises ever came from my cars like you are describing. I would start with replacing the mount. Then check your tq arm bushings and mounts. If you dont find anything there check out the rear end. Also go with 3 degrees on the shaft.
03-08-2011, 08:14 PM
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My buddy's RX-7 has IRS with LS1 swap and the car had a torque arm.......he said it was factory.....it didnt mount to tranny. Since your car has a Cobra diff mounted solid, Im sure theres a lot of noises coming from drivetrain.
03-08-2011, 08:15 PM
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My setup is in an RX-7, so no torque arm. I have a mustang cobra 8.8 IRS diff mounted in my car, nearly solid. The trans also mounts directly to my body, where a trans mount wasn't designed to be. I think thats why I have the noise transmitted to my chassis so much. Not sure. I went with 1.5 degrees since neither my trans or rear end moves, at all. Would you still go with 3 deg, with everything solid mounted on an IRS car?
03-08-2011, 09:52 PM
#7
i dont think the movement in the tailhousing is excessive and prob. not causing any problems but someone does make a heavy duty tail bushing that fixes excessive movement if you need one later on
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03-08-2011, 11:24 PM
#8
Are you sure the yoke is moving in the tailshaft or is the u-joint moving? From what I saw in the video I would take the driveshaft out and check the u-joint. If it's the tailshaft for sure it could have been the angle because it looked like a u-joint issue to me.
The noise is weird and that's also what makes me think u-joints. If it was the tailshaft you would have a whale of a vibration.
The noise is weird and that's also what makes me think u-joints. If it was the tailshaft you would have a whale of a vibration.
03-09-2011, 12:18 AM
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That is very normal movement.. I doubt that the U joints have failed. You would have a clicking or a vibration... If you really want to, just replace them.. Its easy and cheap.
Could the backlash on your rear gears be off here guys?? I would think you would get a clunking/knocking if that were going on. His setup is so solid I would imagine that it could produce a knocking noise..
Is it a constant knocking (knock, knock, knock) or is it only when the gearset is loaded and then unloaded??
If it is a constant knock, is it speed or rpm sensitive?
Could the backlash on your rear gears be off here guys?? I would think you would get a clunking/knocking if that were going on. His setup is so solid I would imagine that it could produce a knocking noise..
Is it a constant knocking (knock, knock, knock) or is it only when the gearset is loaded and then unloaded??
If it is a constant knock, is it speed or rpm sensitive?
03-09-2011, 12:25 AM
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The knocking is only when loading/unloading. To me it always sounded like an extreme stack up of backlash in the drivetrain (clutch disc springs, trans gears, diff gears, diff tripods). When loading and unloading I figured it would all smack together in one direction, then smack in the other, transmitting a hellacious noise in the cabin. Its been this way since the day I got the car together (~4 years ago). I never thought much about it recently till I removed my exhaust to start building a new exhaust setup and noticed it.
My diff gears are setup with 0.010" backlash. When I changed to the 4.10s I was hoping that the stock 3.55s had a ton of backlash and I'd be able to get rid of the clunking/knocking noise but nope. I've had passengers ask me "what is banging under the car" when it happens. Seems to be common for people that do these swaps.
Thanks for relieving my "worst case" thoughts, thinking I had to pull the trans and rebuild.
My diff gears are setup with 0.010" backlash. When I changed to the 4.10s I was hoping that the stock 3.55s had a ton of backlash and I'd be able to get rid of the clunking/knocking noise but nope. I've had passengers ask me "what is banging under the car" when it happens. Seems to be common for people that do these swaps.
Thanks for relieving my "worst case" thoughts, thinking I had to pull the trans and rebuild.
03-09-2011, 10:06 AM
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I know the video looks misleading, but there is no lateral play in the U-joint. All teh movement is from the yoke rocking inside the transmission.
03-09-2011, 12:16 PM
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https://ls1tech.com/forums/manual-tr...t-bushing.htmlUsually if the slip yoke is not scarred or worn down, it's good. Comparing the wear section to the part that remains outside the transmission would give you some idea if it's worn down.
03-09-2011, 04:40 PM
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Doe, I have all my trannys including the one in my car currently (bc I checked it as well becoming concerned after the inception of this thread) doing the same thing as yours and I do not get any clucking.. The only clunking I have ever heard from a driveline like you describe once was a broken tq arm bushing (which you dont have) and excessive backlash in the rear (which you have had checked twice with same problem going on).. Therefore I am stumped without actually being able to look at the car..
Im my mind I have ruled out
The Rear Backlash (if what you say is true about current settings)
The U joints
The Output shaft
Some Cobras came with 12mm bolts from the factory, but the holes in the bushings accept 14mm bolts. Make sure they are 14's.
The rear IRS bushing at the rear diff cover, rips. That causes clunking too. Check that, and replace it with poly bushings if they have failed. One for the rear and two for the front.
Did you ever determine whether the poly bushing was bad or not?
When the car knocks can you feel it in the whole car or just the shifter?
Does it do it consistently enough that you could put the car on a lifft and run it through the gears to find the knock general area?
Is it possible you have a bad suspention bushing/loose bolt? This is what I would move on to next..
Im my mind I have ruled out
The Rear Backlash (if what you say is true about current settings)
The U joints
The Output shaft
Some Cobras came with 12mm bolts from the factory, but the holes in the bushings accept 14mm bolts. Make sure they are 14's.
The rear IRS bushing at the rear diff cover, rips. That causes clunking too. Check that, and replace it with poly bushings if they have failed. One for the rear and two for the front.
Did you ever determine whether the poly bushing was bad or not?
When the car knocks can you feel it in the whole car or just the shifter?
Does it do it consistently enough that you could put the car on a lifft and run it through the gears to find the knock general area?
Is it possible you have a bad suspention bushing/loose bolt? This is what I would move on to next..
Last edited by Sargeant Sh!tbag; 03-09-2011 at 04:48 PM.
