Weird vibration source FOUND!
Thread Starter
Burning Brakes
Joined: Mar 2008
Posts: 859
Likes: 53
From: Magnolia Texas
Weird vibration source FOUND!
I have been chasing a high speed vibration or “buzz” ever since I installed the ZZ454 and Tremec TKO600 transmission in my ’67 convertible. The “problem” manifests itself under moderate load in 3rd or 4th gear at about 2200 RPM and up. It also can be felt in 5th gear at about 75 mph or so. It was most noticeable in the floorboards at the driver’s feet. A passenger typically has a hard time feeling it. It has at time been severe enough to vibrate the rear-view mirror.
I thought for a while it was related to driveshaft angle and tried setting it at various angles, finally settling with the transmission tail shaft as high as I could get it. This was driven largely by the exhaust pipe hanger bracket. Hurst Driveline Conversions provided two spacers for this mount and using both spacers supplied for the transmission mount, the exhaust pipes were still low enough to occasionally vibrate against the clearance holes through the frame so I added an additional 1/8 inch of spacers between the rubber transmission mount and the frame bracket. While that seemed to help with the problem, it was still there to a degree. The odd thing was that if I unloaded the engine just a little, there is NO vibration at all which made me think it was not driveshaft related.
The next place I looked was the motor mounts. When I installed the 454, I was not able to find replacements mounts like the ones I used with the original 427 which were the old “standard” Chevy captured mount but no one seemed to have them anymore. The vendors SAID the replacements were correct but they were very flimsy and very thin compared to the originals so I went to NAPA and found a truck mount that was much more substantial but required the addition of washers on the bolt to take up the space between the mount and the frame. I also found the through bolt was not threaded long enough and was not holding the mount tightly against the frame. An additional washer under the nut took care of that which seemed to help the problem but, it was still there to a degree.
After driving the car for a while, it occurred to me that the fact that it was felt mostly at the driver’s feet was a clue. Also, I reasoned that the clutch cross shaft was the ONLY metal to metal contact of the running gear to the frame AND it connected to the frame right at the driver’s feet. The installed end play of the cross shaft is controlled by two nylon bushings that capture the ball on the frame end of the cross shaft but after removing the nut so the shaft could be moved back and forth, I found the stack-up end-play in my shaft to be essentially zero! I asked Roy (67-427ci) who has the same setup in his ’67 coupe, if he would measure the end-play in his clutch cross shaft which he very accommodatingly did for me, and reported that his end-play was about 5/16 of an inch. I remember thinking the clearance was “tight” when I installed the cross shaft while installing the engine but the ramification of that never occurred to me.
My ZZ454 does not have a boss cast into the block for the clutch cross shaft ball (I have heard the new ones do but mine doesn’t) so I used the (VERY nicely made) Scoggins Dickey bracket to provide the engine-side mount. I removed the cross shaft and the Scoggins Dickey bracket and found “witness marks” on the ball where the ball had been driven HARD into the bottom of the counter bore of the cross shaft. In addition, the nut on the back of the stud showed evidence of having been pushed HARD into the block.
After thinking about this for a while, I sent the cross shaft to a friend of mine who is a EXCELLENT machinist and he extended the counter bore another 3/8 inch or so to provide additional clearance. I reinstalled the cross shaft and took the car for a drive. SUCCESS!!! No more high speed vibration!!!
The message here is to be sure to check the end play of the clutch cross shaft before you install the nut on the frame end because if you don’t have enough end play, you might possibly have a vibration that is VERY difficult to find.
Steve
I thought for a while it was related to driveshaft angle and tried setting it at various angles, finally settling with the transmission tail shaft as high as I could get it. This was driven largely by the exhaust pipe hanger bracket. Hurst Driveline Conversions provided two spacers for this mount and using both spacers supplied for the transmission mount, the exhaust pipes were still low enough to occasionally vibrate against the clearance holes through the frame so I added an additional 1/8 inch of spacers between the rubber transmission mount and the frame bracket. While that seemed to help with the problem, it was still there to a degree. The odd thing was that if I unloaded the engine just a little, there is NO vibration at all which made me think it was not driveshaft related.
The next place I looked was the motor mounts. When I installed the 454, I was not able to find replacements mounts like the ones I used with the original 427 which were the old “standard” Chevy captured mount but no one seemed to have them anymore. The vendors SAID the replacements were correct but they were very flimsy and very thin compared to the originals so I went to NAPA and found a truck mount that was much more substantial but required the addition of washers on the bolt to take up the space between the mount and the frame. I also found the through bolt was not threaded long enough and was not holding the mount tightly against the frame. An additional washer under the nut took care of that which seemed to help the problem but, it was still there to a degree.
After driving the car for a while, it occurred to me that the fact that it was felt mostly at the driver’s feet was a clue. Also, I reasoned that the clutch cross shaft was the ONLY metal to metal contact of the running gear to the frame AND it connected to the frame right at the driver’s feet. The installed end play of the cross shaft is controlled by two nylon bushings that capture the ball on the frame end of the cross shaft but after removing the nut so the shaft could be moved back and forth, I found the stack-up end-play in my shaft to be essentially zero! I asked Roy (67-427ci) who has the same setup in his ’67 coupe, if he would measure the end-play in his clutch cross shaft which he very accommodatingly did for me, and reported that his end-play was about 5/16 of an inch. I remember thinking the clearance was “tight” when I installed the cross shaft while installing the engine but the ramification of that never occurred to me.
My ZZ454 does not have a boss cast into the block for the clutch cross shaft ball (I have heard the new ones do but mine doesn’t) so I used the (VERY nicely made) Scoggins Dickey bracket to provide the engine-side mount. I removed the cross shaft and the Scoggins Dickey bracket and found “witness marks” on the ball where the ball had been driven HARD into the bottom of the counter bore of the cross shaft. In addition, the nut on the back of the stud showed evidence of having been pushed HARD into the block.
After thinking about this for a while, I sent the cross shaft to a friend of mine who is a EXCELLENT machinist and he extended the counter bore another 3/8 inch or so to provide additional clearance. I reinstalled the cross shaft and took the car for a drive. SUCCESS!!! No more high speed vibration!!!
The message here is to be sure to check the end play of the clutch cross shaft before you install the nut on the frame end because if you don’t have enough end play, you might possibly have a vibration that is VERY difficult to find.
Steve
Last edited by 67*427; Jun 24, 2010 at 04:52 PM.
Melting Slicks
Joined: Apr 2003
Posts: 2,830
Likes: 491
From: Florida
Someone here a few weeks back had the engine clutch pivot stud break while driving. Others noted this has happened to them in the past. I ordered all new parts for mine after reading that. After that hammering you might want to replace yours too.
Pro
Joined: Nov 2006
Posts: 677
Likes: 0
From: Davie FL
I have been chasing a high speed vibration or “buzz” ever since I installed the ZZ454 and Tremec TKO600 transmission in my ’67 convertible. The “problem” manifests itself under moderate load in 3rd or 4th gear at about 2200 RPM and up. It also can be felt in 5th gear at about 75 mph or so. It was most noticeable in the floorboards at the driver’s feet. A passenger typically has a hard time feeling it. It has at time been severe enough to vibrate the rear-view mirror.
I thought for a while it was related to driveshaft angle and tried setting it at various angles, finally settling with the transmission tail shaft as high as I could get it. This was driven largely by the exhaust pipe hanger bracket. Hurst Driveline Conversions provided two spacers for this mount and using both spacers supplied for the transmission mount, the exhaust pipes were still low enough to occasionally vibrate against the clearance holes through the frame so I added an additional 1/8 inch of spacers between the rubber transmission mount and the frame bracket. While that seemed to help with the problem, it was still there to a degree. The odd thing was that if I unloaded the engine just a little, there is NO vibration at all which made me think it was not driveshaft related.
The next place I looked was the motor mounts. When I installed the 454, I was not able to find replacements mounts like the ones I used with the original 427 which were the old “standard” Chevy captured mount but no one seemed to have them anymore. The vendors SAID the replacements were correct but they were very flimsy and very thin compared to the originals so I went to NAPA and found a truck mount that was much more substantial but required the addition of washers on the bolt to take up the space between the mount and the frame. I also found the through bolt was not threaded long enough and was not holding the mount tightly against the frame. An additional washer under the nut took care of that which seemed to help the problem but, it was still there to a degree.
After driving the car for a while, it occurred to me that the fact that it was felt mostly at the driver’s feet was a clue. Also, I reasoned that the clutch cross shaft was the ONLY metal to metal contact of the running gear to the frame AND it connected to the frame right at the driver’s feet. The installed end play of the cross shaft is controlled by two nylon bushings that capture the ball on the frame end of the cross shaft but after removing the nut so the shaft could be moved back and forth, I found the stack-up end-play in my shaft to be essentially zero! I asked Roy (67-427ci) who has the same setup in his ’67 coupe, if he would measure the end-play in his clutch cross shaft which he very accommodatingly did for me, and reported that his end-play was about 5/16 of an inch. I remember thinking the clearance was “tight” when I installed the cross shaft while installing the engine but the ramification of that never occurred to me.
My ZZ454 does not have a boss cast into the block for the clutch cross shaft ball (I have heard the new ones do but mine doesn’t) so I used the (VERY nicely made) Scoggins Dickey bracket to provide the engine-side mount. I removed the cross shaft and the Scoggins Dickey bracket and found “witness marks” on the ball where the ball had been driven HARD into the bottom of the counter bore of the cross shaft. In addition, the nut on the back of the stud showed evidence of having been pushed HARD into the block.
After thinking about this for a while, I sent the cross shaft to a friend of mine who is a EXCELLENT machinist and he extended the counter bore another 3/8 inch or so to provide additional clearance. I reinstalled the cross shaft and took the car for a drive. SUCCESS!!! No more high speed vibration!!!
The message here is to be sure to check the end play of the clutch cross shaft before you install the nut on the frame end because if you don’t have enough end play, you might possibly have a vibration that is VERY difficult to find.
Steve
I thought for a while it was related to driveshaft angle and tried setting it at various angles, finally settling with the transmission tail shaft as high as I could get it. This was driven largely by the exhaust pipe hanger bracket. Hurst Driveline Conversions provided two spacers for this mount and using both spacers supplied for the transmission mount, the exhaust pipes were still low enough to occasionally vibrate against the clearance holes through the frame so I added an additional 1/8 inch of spacers between the rubber transmission mount and the frame bracket. While that seemed to help with the problem, it was still there to a degree. The odd thing was that if I unloaded the engine just a little, there is NO vibration at all which made me think it was not driveshaft related.
The next place I looked was the motor mounts. When I installed the 454, I was not able to find replacements mounts like the ones I used with the original 427 which were the old “standard” Chevy captured mount but no one seemed to have them anymore. The vendors SAID the replacements were correct but they were very flimsy and very thin compared to the originals so I went to NAPA and found a truck mount that was much more substantial but required the addition of washers on the bolt to take up the space between the mount and the frame. I also found the through bolt was not threaded long enough and was not holding the mount tightly against the frame. An additional washer under the nut took care of that which seemed to help the problem but, it was still there to a degree.
After driving the car for a while, it occurred to me that the fact that it was felt mostly at the driver’s feet was a clue. Also, I reasoned that the clutch cross shaft was the ONLY metal to metal contact of the running gear to the frame AND it connected to the frame right at the driver’s feet. The installed end play of the cross shaft is controlled by two nylon bushings that capture the ball on the frame end of the cross shaft but after removing the nut so the shaft could be moved back and forth, I found the stack-up end-play in my shaft to be essentially zero! I asked Roy (67-427ci) who has the same setup in his ’67 coupe, if he would measure the end-play in his clutch cross shaft which he very accommodatingly did for me, and reported that his end-play was about 5/16 of an inch. I remember thinking the clearance was “tight” when I installed the cross shaft while installing the engine but the ramification of that never occurred to me.
My ZZ454 does not have a boss cast into the block for the clutch cross shaft ball (I have heard the new ones do but mine doesn’t) so I used the (VERY nicely made) Scoggins Dickey bracket to provide the engine-side mount. I removed the cross shaft and the Scoggins Dickey bracket and found “witness marks” on the ball where the ball had been driven HARD into the bottom of the counter bore of the cross shaft. In addition, the nut on the back of the stud showed evidence of having been pushed HARD into the block.
After thinking about this for a while, I sent the cross shaft to a friend of mine who is a EXCELLENT machinist and he extended the counter bore another 3/8 inch or so to provide additional clearance. I reinstalled the cross shaft and took the car for a drive. SUCCESS!!! No more high speed vibration!!!
The message here is to be sure to check the end play of the clutch cross shaft before you install the nut on the frame end because if you don’t have enough end play, you might possibly have a vibration that is VERY difficult to find.
Steve
Steve I was reading your thread and had to pause for a little bit. I was about ready to order new half shafts and a new driveshaft to see if I can get rid of that annoying vibration at 40+mph.I also have the zz454 and have talked to Roy previously on some other engine related things.I remember putting in the clutch cross shaft and it was a sob.I might have found the problem. Is there anyway you can take a picture of what you did and post it? thanks Vic Z.
Thread Starter
Burning Brakes
Joined: Mar 2008
Posts: 859
Likes: 53
From: Magnolia Texas
Hi Vic z,
The cross shaft is back in the car so there isn't much to photograph. If your shaft has little or no end play, take it out of the car and have someone machine the COUNTERBORE on the engine end of that shaft so the ball on that end will go DEEPER into the shaft. In my case, I had about 3/8 of an inch machined out. What this did was allow the shaft to have some end play once it was back in the car.
Does that make sense???
Steve
The cross shaft is back in the car so there isn't much to photograph. If your shaft has little or no end play, take it out of the car and have someone machine the COUNTERBORE on the engine end of that shaft so the ball on that end will go DEEPER into the shaft. In my case, I had about 3/8 of an inch machined out. What this did was allow the shaft to have some end play once it was back in the car.
Does that make sense???
Steve
Le Mans Master
Joined: Sep 2003
Posts: 8,934
Likes: 657
From: Norwalk ohio
2019 Corvette of the Year Winner
St. Jude Donor '15
I have a 383 and TKO600. I don't get any vibrations if I am in 5th gear running around 70 mph. If I am down around 55mph then I get a vibration that makes me want to shift back to 4th gear and the vibration goes away....does this sound familiar to you? or is this different?
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Thread Starter
Burning Brakes
Joined: Mar 2008
Posts: 859
Likes: 53
From: Magnolia Texas
Firstgear....
That's different than mine was. Mine was under LIGHT load that started around 2200 and up. Under no load or full load, it wasn't bad. Most notable in 3rd and 4th.
Steve
That's different than mine was. Mine was under LIGHT load that started around 2200 and up. Under no load or full load, it wasn't bad. Most notable in 3rd and 4th.
Steve
Le Mans Master
Joined: Sep 2003
Posts: 8,934
Likes: 657
From: Norwalk ohio
2019 Corvette of the Year Winner
St. Jude Donor '15
Pro
Joined: Nov 2006
Posts: 677
Likes: 0
From: Davie FL
Yes we did Mike. I was concerned since it might have been in there so tight that it could have been binding.This was a great catch by Steve !!. I do have a 1/4" to 5/16" gap. To eliminate this pesky vibration,something tells me that the driveshaft needs balancing or the weight fell off. I have had the tires shaved and balanced by the GSP9700Hunter machine.
Melting Slicks
Joined: May 2005
Posts: 2,826
Likes: 3
From: Tennessee
I have a 383 and TKO600. I don't get any vibrations if I am in 5th gear running around 70 mph. If I am down around 55mph then I get a vibration that makes me want to shift back to 4th gear and the vibration goes away....does this sound familiar to you? or is this different?
A vibration that is more rpm related usually points to the driveline angle.
