shaking/vibration during hard acceleration
Thread Starter
Melting Slicks
Joined: May 2002
Posts: 3,210
Likes: 1
shaking/vibration during hard acceleration
This afternoon I went to the drag strip and noticed that I'm getting a shaking/vibration at speed which is causing the car to be very unstable in 3rd-6th gear.
Here is the deal, I can launch fine and the 1-2 shift is OK. the problem is once I shift into 3rd gear and go WOT, the rear of the car feels like its shaking/unstable and it wants to come around on me. As a result I can't keep the car straight and stay on the gas at the same time, I almost lost control of the car a couple of times today. It only happens above a specific speed or when I'm in 3rd thru 6th and accelerating, it won't to it in 1st or 2nd at all.
I think the reason that it doesn't do it in 1st or 2nd is because the car isn't moving fast enough. Also, I'm thinking it might be a suspension or alignment issue, and not something related to the driveline, because on the ride home if I put the car in neutral and coasted the shaking feeling was still there even though the car wasn't in gear.
has anyone experienced anything like this before or have any ideas?
Here is the deal, I can launch fine and the 1-2 shift is OK. the problem is once I shift into 3rd gear and go WOT, the rear of the car feels like its shaking/unstable and it wants to come around on me. As a result I can't keep the car straight and stay on the gas at the same time, I almost lost control of the car a couple of times today. It only happens above a specific speed or when I'm in 3rd thru 6th and accelerating, it won't to it in 1st or 2nd at all.
I think the reason that it doesn't do it in 1st or 2nd is because the car isn't moving fast enough. Also, I'm thinking it might be a suspension or alignment issue, and not something related to the driveline, because on the ride home if I put the car in neutral and coasted the shaking feeling was still there even though the car wasn't in gear.
has anyone experienced anything like this before or have any ideas?
Thread Starter
Melting Slicks
Joined: May 2002
Posts: 3,210
Likes: 1
I should have mentioned in my first post the tire pressure was equal on both axles. when I got back to the pits that was the first thing I checked.
The tires I'm running are MT ET Streets which are 2 ply. I don't think they are coming apart internally but I guess I don't know for sure.
The shocks are OEM z06 units. I don't feel or hear anything unusual when I'm turning at spped but I wonder if there is a way to check if a shock is busted.
Race Director
Joined: Aug 2000
Posts: 10,649
Likes: 31
From: Central Florida
Are the MT ET Streets radials or bias-ply?
If the rears are bias-ply and the fronts are radial, that is the issue. And it is a combo normally avoided by racers who are judicious with risk. The recommended front tires to run with MT bias-ply are typically skinny bias-ply.
A quick test is to remount the stock rear tires (e.g. non-MT) and go for a drive. If the issue is still there, root cause is not the tires. If symptoms do disappear, the rear-to-front tire-construction mismatch is the likely cause.
Ranger
If the rears are bias-ply and the fronts are radial, that is the issue. And it is a combo normally avoided by racers who are judicious with risk. The recommended front tires to run with MT bias-ply are typically skinny bias-ply.
A quick test is to remount the stock rear tires (e.g. non-MT) and go for a drive. If the issue is still there, root cause is not the tires. If symptoms do disappear, the rear-to-front tire-construction mismatch is the likely cause.
Ranger
Last edited by Ranger; Aug 5, 2007 at 07:34 AM.
Racer
Joined: Aug 2003
Posts: 484
Likes: 1
From: Merrimack NH
Happened to me this summer and it's not a lot of fun when it happened. Obviously ranger is right about not mixing tires. I'll assume youre not doing that. Check all suspension to make sure everything is tight. My problem turned out to be the steering rack.
Burning Brakes
Joined: Oct 2004
Posts: 792
Likes: 19
From: ME
And if you find that putting your regular tires and wheels on doesn't fix the issue then my first guess would be your driveshaft bushings. Are you running heads and cam? Any heavy mods? By trend on this forum I find 100% of the guys with big modifications are ripping their driveshaft bushings apart. The symptoms are EXACTLY as you describe.
Racer
Joined: Aug 2003
Posts: 484
Likes: 1
From: Merrimack NH
And if you find that putting your regular tires and wheels on doesn't fix the issue then my first guess would be your driveshaft bushings. Are you running heads and cam? Any heavy mods? By trend on this forum I find 100% of the guys with big modifications are ripping their driveshaft bushings apart. The symptoms are EXACTLY as you describe.
Thread Starter
Melting Slicks
Joined: May 2002
Posts: 3,210
Likes: 1
With the stock Z06 rims on the car I can still feel the shaking/vibration I described above but its not as harsh or pronounced as with the drag pack on there. Part of the reason I suspect it not as bad w/stock rims is because I can't really 'get on it' with the stock F1 super cup tires w/o breaking traction on the street. If I was able to go WOT in 3rd w/o spinning it would probably be the same.
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Thread Starter
Melting Slicks
Joined: May 2002
Posts: 3,210
Likes: 1
My shaking/vibration seems to be coming from the rear of the car even though I can still feel it a little in the steering wheel. When I was going down the track I had the front of the car pointing straight, but when I would go WOT I could feel the rear end start to come around like I didn't have traction but I know I did.
Thread Starter
Melting Slicks
Joined: May 2002
Posts: 3,210
Likes: 1
And if you find that putting your regular tires and wheels on doesn't fix the issue then my first guess would be your driveshaft bushings. Are you running heads and cam? Any heavy mods? By trend on this forum I find 100% of the guys with big modifications are ripping their driveshaft bushings apart. The symptoms are EXACTLY as you describe.
So you suspect the driveshaft bushings, that would make sense, can you point me in the direction of some posts where people experienced the same symptoms as me?
I don't know if mine are stock or upgraded. I assume they are stock because nothing was mentioned about them being upgraded when I purchased the car.
Race Director
Joined: Aug 2000
Posts: 10,649
Likes: 31
From: Central Florida
http://forums.corvetteforum.com/showthread.php?t=151702
http://forums.corvetteforum.com/show....php?t=1571081
Good shots of the couplers too. http://forums.corvetteforum.com/show....php?t=1770766
Ranger
Last edited by Ranger; Aug 5, 2007 at 12:10 PM.
Thread Starter
Melting Slicks
Joined: May 2002
Posts: 3,210
Likes: 1
looks like servohead got it right on the money. According to the symptoms described in that thread my bushings are shot. It makes sense too, since I've had the car I absued it with about 20 - 10sec passes most with 1.5 or better 60's. That kind of shock to the driveline is bound to stress those stock rubber units.
Now to decide whether to upgrade to solid billet aluminum ones from LGM or the U-joint from ECS...
Racer
Joined: Aug 2003
Posts: 484
Likes: 1
From: Merrimack NH
what kind of symptoms did you have? was there anything you noticed @ low speed while turning?
My shaking/vibration seems to be coming from the rear of the car even though I can still feel it a little in the steering wheel. When I was going down the track I had the front of the car pointing straight, but when I would go WOT I could feel the rear end start to come around like I didn't have traction but I know I did.
My shaking/vibration seems to be coming from the rear of the car even though I can still feel it a little in the steering wheel. When I was going down the track I had the front of the car pointing straight, but when I would go WOT I could feel the rear end start to come around like I didn't have traction but I know I did.
Last edited by BrentNY; Aug 5, 2007 at 09:31 PM. Reason: spelling
Burning Brakes
Joined: Oct 2004
Posts: 792
Likes: 19
From: ME
Well now knowing what kind of 1/4 times you're running, WOW! I would have thought that you'd have ripped those couplers right out of the car after the 2nd pass! Darn chevy's making too much horsepower again... Get some better ones in there! You'll see, I hear the best setup is to only use one alluminum coupler as if you put 2 then you'll have driveline vibration issues.
Good luck, glad I could be of help to you! Now if I could just fix my car!!
Get some better ones in there! You'll see, I hear the best setup is to only use one alluminum coupler as if you put 2 then you'll have driveline vibration issues.Good luck, glad I could be of help to you! Now if I could just fix my car!!
Thread Starter
Melting Slicks
Joined: May 2002
Posts: 3,210
Likes: 1
Thread Starter
Melting Slicks
Joined: May 2002
Posts: 3,210
Likes: 1
Update:
update:
I pulled the drivetrain out this weekend and to my surprise the torque tube couplers were in perfect shape. They both look brand spanking new
I'm going to install a new aluminum bushing while I have the thing apart anyway but I guess its back to square one. I really don't want to put the car back together at this point just to have the same problem under WOT. I'm open for suggestions...
Some things I noticed that might be contributors to what I'm feeling:
The boot on the tie rod of the DS rear is ripped and the balljoint boot on the PS rear is ripped also.
Both of happend on the very first time I removed the trans because I used a seperator fork to remove them
. I know now that there is a much faster/easier way to drop the rear w/o having to do that. Needless to say they will be getting replaced before everything goes back in. Could this have caused the symptoms I was feeling??
I pulled the drivetrain out this weekend and to my surprise the torque tube couplers were in perfect shape. They both look brand spanking new
I'm going to install a new aluminum bushing while I have the thing apart anyway but I guess its back to square one. I really don't want to put the car back together at this point just to have the same problem under WOT. I'm open for suggestions...
Some things I noticed that might be contributors to what I'm feeling:
The boot on the tie rod of the DS rear is ripped and the balljoint boot on the PS rear is ripped also.
Both of happend on the very first time I removed the trans because I used a seperator fork to remove them
. I know now that there is a much faster/easier way to drop the rear w/o having to do that. Needless to say they will be getting replaced before everything goes back in. Could this have caused the symptoms I was feeling??
Thread Starter
Melting Slicks
Joined: May 2002
Posts: 3,210
Likes: 1
Update
I hope I don't jinx myself by posting this but I figured down the road if anyone is experiencing the same thing it might be useful to know.
It appears I fixed the problem. I've been driving around all weekend beating the car and there is no vibration from the driveline what so ever
Turns out it was either too much play from the tie-rod ends having ripped boots, too much play from the pass side lower ball joint having a ripped boot, or a combination of both. Whatever the case maybe I replaced all the above last Friday night and that did the trick. It feels awesome being able to go WOT again, I forgot what it was like to lose traction in 3rd gear
. All I need is an alignment which I hope to get this week sometime and she will be perfect once again.
It appears I fixed the problem. I've been driving around all weekend beating the car and there is no vibration from the driveline what so ever
Turns out it was either too much play from the tie-rod ends having ripped boots, too much play from the pass side lower ball joint having a ripped boot, or a combination of both. Whatever the case maybe I replaced all the above last Friday night and that did the trick. It feels awesome being able to go WOT again, I forgot what it was like to lose traction in 3rd gear
. All I need is an alignment which I hope to get this week sometime and she will be perfect once again.
