Alarming vibration from the rear end
07-02-2015, 07:52 PM
#1
Instructor
Thread Starter
Alarming vibration from the rear end
After finally tuning up properly distributor and carburetor, went for a ride to enjoy the car.
Well, cruising at 50 was fine and the engine runs strong asking for more, but when i started going over the 60 I could hear and fell the rear shaking and growing worse till when reaching 80 where it become pretty alarming.
Went soon after to the tire shop to check for balance on rear wheels. They found out that the wheels were way out of balance. So fixed the problem went again to test the car but the vibration was still there.
What should I check? What could be the faulty part?
Suggestions?
Btw it's a 67 coupe 327/300
Well, cruising at 50 was fine and the engine runs strong asking for more, but when i started going over the 60 I could hear and fell the rear shaking and growing worse till when reaching 80 where it become pretty alarming.
Went soon after to the tire shop to check for balance on rear wheels. They found out that the wheels were way out of balance. So fixed the problem went again to test the car but the vibration was still there.
What should I check? What could be the faulty part?
Suggestions?
Btw it's a 67 coupe 327/300
Last edited by V8Heart; 07-02-2015 at 07:58 PM.
07-02-2015, 07:54 PM
#2
Team Owner
Not a soul can help you without knowing what year car. C1 and C2 rears are completely different beasts. No clairvoyants on the forum I'm afraid.
07-02-2015, 07:56 PM
#3
Le Mans Master
Is this for the '68 you have in your profile? Did this problem show up only after tuning the car? Sounds like the u-joints in the half-shafts.
07-02-2015, 07:59 PM
#4
Team Owner
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I'm assuming that the tire shop did a full dynamic balance? The one where they spin the tire and wheel at speed?
Has anything else been changed recently?
Did you feel any "kicking" in the steering wheel? Or did it feel more in the center or in the rear end?
Did you tap the brakes while this vibration was occurring? If so, what were the symptoms then?
Any new unusual noises?
I would start with checking wheel bearings, and drive shaft and half shaft balance.
Has anything else been changed recently?
Did you feel any "kicking" in the steering wheel? Or did it feel more in the center or in the rear end?
Did you tap the brakes while this vibration was occurring? If so, what were the symptoms then?
Any new unusual noises?
I would start with checking wheel bearings, and drive shaft and half shaft balance.
07-02-2015, 08:00 PM
#5
Instructor
Thread Starter
Well I couldn't have tested the car before I solved the problems with distributor/carburetor so that was my actual first test drive.
Any specific reasons why you mention the u-joints?
07-02-2015, 08:02 PM
#6
Instructor
Thread Starter
07-02-2015, 08:04 PM
#7
Team Owner
I have no idea where Vesuvio is but if your tire shop didn't have one of these:
http://www.gsp9700.com/ then find one that does.
Check that those tire guys torqued the wheels on properly as well...most shops are now pretty safety (and liability) conscious about that now - but not everybody...
Also there is a LOT going on in the rear of C2s so you need somebody that really knows their way around to check it out for you it it turns out to NOT be tires.
The suggestion about U-joints is spot on - that's the next thing to check (or have checked)..
http://www.gsp9700.com/ then find one that does.
Check that those tire guys torqued the wheels on properly as well...most shops are now pretty safety (and liability) conscious about that now - but not everybody...
Also there is a LOT going on in the rear of C2s so you need somebody that really knows their way around to check it out for you it it turns out to NOT be tires.
The suggestion about U-joints is spot on - that's the next thing to check (or have checked)..
07-02-2015, 08:08 PM
#8
Instructor
Thread Starter
I'm assuming that the tire shop did a full dynamic balance? The one where they spin the tire and wheel at speed? yes
Has anything else been changed recently? apart from removing the spare tire carrier, I haven't touched anything -I should ask the previous owner
Did you feel any "kicking" in the steering wheel? Or did it feel more in the center or in the rear end? rear, the front is very steady also because doesn't have power steering
Did you tap the brakes while this vibration was occurring? If so, what were the symptoms then? will try
Any new unusual noises? there has always been a ticking sound while moving since I bought the car -it goes off if while driving I push the clutch or put the car in neutral, don't know if it is linked to the vibration
I would start with checking wheel bearings, and drive shaft and half shaft balance. definitely
Has anything else been changed recently? apart from removing the spare tire carrier, I haven't touched anything -I should ask the previous owner
Did you feel any "kicking" in the steering wheel? Or did it feel more in the center or in the rear end? rear, the front is very steady also because doesn't have power steering
Did you tap the brakes while this vibration was occurring? If so, what were the symptoms then? will try
Any new unusual noises? there has always been a ticking sound while moving since I bought the car -it goes off if while driving I push the clutch or put the car in neutral, don't know if it is linked to the vibration
I would start with checking wheel bearings, and drive shaft and half shaft balance. definitely
07-02-2015, 08:12 PM
#9
Instructor
Thread Starter
I have no idea where Vesuvio is but if your tire shop didn't have one of these:
http://www.gsp9700.com/ then find one that does.
Check that those tire guys torqued the wheels on properly as well...most shops are now pretty safety (and liability) conscious about that now - but not everybody...
Also there is a LOT going on in the rear of C2s so you need somebody that really knows their way around to check it out for you it it turns out to NOT be tires.
The suggestion about U-joints is spot on - that's the next thing to check (or have checked)..
http://www.gsp9700.com/ then find one that does.
Check that those tire guys torqued the wheels on properly as well...most shops are now pretty safety (and liability) conscious about that now - but not everybody...
Also there is a LOT going on in the rear of C2s so you need somebody that really knows their way around to check it out for you it it turns out to NOT be tires.
The suggestion about U-joints is spot on - that's the next thing to check (or have checked)..
Vesuvio is the volcano near where I live, in Italy.
Can we include in the list the clutch?
07-02-2015, 10:12 PM
#10
Le Mans Master
Re-read post #3. The slight ticking you heard prior to the violent vibration in the rear was probably the needle bearings in the u-joints falling out
BTW, I just got back from your beautiful country. Spent some of the time on the Amalfi coast staring at Mt. Vesuvius while boating out to Capri.
BTW, I just got back from your beautiful country. Spent some of the time on the Amalfi coast staring at Mt. Vesuvius while boating out to Capri.
07-02-2015, 10:49 PM
#11
Team Owner
Here is some info that may help you isolate your problem...
07-02-2015, 11:02 PM
#12
Team Owner
I would have just rotated the rear tires to the front to see if causing vibration
So next go see if there is any shims that fell out, naturally if they did they won't be there so see, so see if there is play in the nose of those arms. hit them side to side with a rubber mallet would be next. Do you remember bouncing the car over any big jarring speed bump or potholes or did you run anyone over lately? halfshaft u-joint going, they will just kind of make a popping, clicking or grind noise as the bad angle rotates around, not really a vibration. Check the rims also to see if any welds broke. the rear bearings would give a whistle, or a hum like a 4x4 tire sound and maybe some detectable play, but not a vibration. i am also thinking of running it with the back end jacked under extreme danger to yourself and put your hand on the diff for vibrations! i am also feeling the tune up is too much of a coincidence. Are you sure the engine isn't missing and it is traveling from the source back thru the drivetrain!
Unfortunately I can only form a clairvoyant connection with your cars, if you have let me drive them!
Unfortunately I can only form a clairvoyant connection with your cars, if you have let me drive them!
Last edited by TCracingCA; 07-02-2015 at 11:57 PM.
07-02-2015, 11:42 PM
#13
Melting Slicks
You might want to check the differential carrier mount. You can get a pretty good vibration if the bushing is bad or if it's loose. I'd also check the half shaft yolks.
Gary
Gary
07-02-2015, 11:50 PM
#14
Team Owner
rear diff bushing is a big clunk sound
usually on initial acceleration or deceleration, and yokes give you the squirrely wiggle not necessarily noisy!
PS check the op on your parking brakes also!
PS check the op on your parking brakes also!
Last edited by TCracingCA; 07-02-2015 at 11:59 PM.
07-02-2015, 11:57 PM
#15
Melting Slicks
07-03-2015, 12:05 AM
#16
Team Owner
ya i hate when i do that!
But what is the proper ettiquette (how many posts do you wait to pass) prior to adding your own two cents!
but those are definitely good things to check, and i have had both of those happen in my personal bucket list! i definitely needed you around back then! Where the heck were you? Come to think about it, where the heck was the Corvette forum back then!sorry!
07-03-2015, 07:08 AM
#17
Team Owner
Gary could be on to something there....it was a bigger problem in the earlier mid-years but some of those differential carriers were unreinforced and if the car was flogged heavily the mount points would wallow out. Sometimes just replacing the units with reinforced versions cleared up vibration/noise issues.
First pic is plain carrier mount; second are reinforced mounts. There was a TSB for this issue covering 63-65 cars. May have been already addressed by the factory on later midyears but it only takes a minute to check
First pic is plain carrier mount; second are reinforced mounts. There was a TSB for this issue covering 63-65 cars. May have been already addressed by the factory on later midyears but it only takes a minute to check
07-03-2015, 07:35 AM
#18
Race Director
I think it's covered in the FAQ threads Frankie posted but I would include checking the rear transmission bushing for excessive wear. Easy to check just grab the yoke behind the transmission and try to move it up/down/laterally. It should be tight with no play (but they often aren't). Also look at the transmission mount to make sure it is in good shape and not separated.
07-03-2015, 01:46 PM
#19
Instructor
Thread Starter
Made some road testing today: the vibration is in function of the speed not the rpm. While at vibration point pushed the clutch and geared in neutral but nothing changed.
Lifting the car I couldn't tell if the trailing arms lost shimming, but there was play on both sides. Can this be the issue?
Hopefully tomorrow I will have some more time to lift the car and check differential bushings and carrier.
Lifting the car I couldn't tell if the trailing arms lost shimming, but there was play on both sides. Can this be the issue?
Hopefully tomorrow I will have some more time to lift the car and check differential bushings and carrier.