New Member- Tech Question
Thread Starter
5th Gear
Joined: May 2011
Posts: 5
Likes: 0
New Member- Tech Question
First off, Hi guys.
My name is Jesse, first time poster here on the forums.
Anyway what brings me here is that my dad purchased a 1987 Z52 corvette. I do not know much about cars, hence why I'm here!
It was always my dad's dream to own a 71 vette or so, but this one had the right price tag on it.
Anyway here's the issue:
We've taken it to multiple mechanics and all have said there are no mechanical problems with the engine. It pulls hard through all the gears (4 + 4 tranny) however there is a somewhat apparent vibration that comes on right about the 3000 rpm mark. The vibration is a pretty high frequency and could be missed by simply haulin through the gears.
The easiest way to feel it is to accelerate in 2nd gear up through the 3k rpm range- it then feels obvious.
We have no idea what is causing this issue, and I was hoping you guys could shed some light on the subject. Again, multiple mechanics have confirmed the motor is running correctly, that there is some sort of other issue causing the vibration. I've heard something about a harmonic balancer? Other variables?
I really appreciate the input, and thanks in advance!
Jesse
My name is Jesse, first time poster here on the forums.
Anyway what brings me here is that my dad purchased a 1987 Z52 corvette. I do not know much about cars, hence why I'm here!
It was always my dad's dream to own a 71 vette or so, but this one had the right price tag on it.
Anyway here's the issue:
We've taken it to multiple mechanics and all have said there are no mechanical problems with the engine. It pulls hard through all the gears (4 + 4 tranny) however there is a somewhat apparent vibration that comes on right about the 3000 rpm mark. The vibration is a pretty high frequency and could be missed by simply haulin through the gears.
The easiest way to feel it is to accelerate in 2nd gear up through the 3k rpm range- it then feels obvious.
We have no idea what is causing this issue, and I was hoping you guys could shed some light on the subject. Again, multiple mechanics have confirmed the motor is running correctly, that there is some sort of other issue causing the vibration. I've heard something about a harmonic balancer? Other variables?
I really appreciate the input, and thanks in advance!
Jesse
Thread Starter
5th Gear
Joined: May 2011
Posts: 5
Likes: 0
It's difficult to say...
We initially thought it was a stutter in the motor, so it feels as if the vibration originates in front end of the car.
It would not surprise me if it could be coming from the drive shaft somehow?
I was surprised when no professional mechanic could pinpoint the cause or location of the issue. It comes on suddenly, as if from the front end. Allegedly not caused by the motor itself.
Are there any components of an 87 that tend to go out over time and can cause this type of vibration? We have no idea where to start.
Once again I appreciate the feedback, I've had great success troubleshooting mechanical issues for my street bike, jet skis, etc. on forums.
Jesse
We initially thought it was a stutter in the motor, so it feels as if the vibration originates in front end of the car.
It would not surprise me if it could be coming from the drive shaft somehow?
I was surprised when no professional mechanic could pinpoint the cause or location of the issue. It comes on suddenly, as if from the front end. Allegedly not caused by the motor itself.
Are there any components of an 87 that tend to go out over time and can cause this type of vibration? We have no idea where to start.
Once again I appreciate the feedback, I've had great success troubleshooting mechanical issues for my street bike, jet skis, etc. on forums.
Jesse
Le Mans Master
Joined: Jul 2007
Posts: 5,356
Likes: 2
From: No HOA, New Hampshire
Cruise-In X Veteran
St. Jude Donor '09
I would look at front bearings, and then wheel/tire balance. It could be as simple as tire pressure. My 88 vibrates @ 50 mph if there is less than 30# in the front tires.
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
You might want to isolate it to see i it is rpm speed or road surface related.
The engine does not care what gear you are in or even i moving i a bad damper lywheel clutch or whatever is out o balance.
If wheels or suspension shaking it will be speed related also the driveshaft and half shafts are speed related not gear position or rpm related.
If it is the tune-up it will miss under a heavy load so slow down to around 20 in third then roll into the throttle hard and see if pulls smoothly up to speed.
Personally I would give it a good tune-up no matter what as it is 24 year old car and unless you know the plugs wires cap and rotor and fuel filter are new and installed correctly they are worth doing for reliability alone. Might as well give it an oil change while at it air the tires up check the spare etc. I would assume nothing and do your own used car recondition service. You should buy a factory service manual (red cover) as well as having a mechanic do everything will get pricey fast. A flat rate mechanic does not want to even see the car as they are not difficult to work on but are time consuming.
The engine does not care what gear you are in or even i moving i a bad damper lywheel clutch or whatever is out o balance.
If wheels or suspension shaking it will be speed related also the driveshaft and half shafts are speed related not gear position or rpm related.
If it is the tune-up it will miss under a heavy load so slow down to around 20 in third then roll into the throttle hard and see if pulls smoothly up to speed.
Personally I would give it a good tune-up no matter what as it is 24 year old car and unless you know the plugs wires cap and rotor and fuel filter are new and installed correctly they are worth doing for reliability alone. Might as well give it an oil change while at it air the tires up check the spare etc. I would assume nothing and do your own used car recondition service. You should buy a factory service manual (red cover) as well as having a mechanic do everything will get pricey fast. A flat rate mechanic does not want to even see the car as they are not difficult to work on but are time consuming.
Thread Starter
5th Gear
Joined: May 2011
Posts: 5
Likes: 0
Sorry I should have made myself more clear,
the vibration is not speed related. It is most apparent at about 3k rpm in second gear, but the vibration can still be felt at approx the same rpm in 1st gear. It can likely be felt at the same rpm in 3rd however I didn't have the chance to get it that far around the suburbia area I live.
The car just had all plugs, wires, cap (no fuel filter yet- but the mechanic said the fuel line pressure was fine?). The car can run under a load uphill with ease. All tire pressures are set at 35lbs or so. Where to go from here?
the vibration is not speed related. It is most apparent at about 3k rpm in second gear, but the vibration can still be felt at approx the same rpm in 1st gear. It can likely be felt at the same rpm in 3rd however I didn't have the chance to get it that far around the suburbia area I live.
The car just had all plugs, wires, cap (no fuel filter yet- but the mechanic said the fuel line pressure was fine?). The car can run under a load uphill with ease. All tire pressures are set at 35lbs or so. Where to go from here?
Burning Brakes
Joined: Feb 2009
Posts: 785
Likes: 3
From: Richmond Virginia
Any mods done--is it completely stock ? I would think if it was engine dampner or fly wheel it would be felt in neutral at around 3K--have you tried that?
You mentioned drive shaft. Has any one checked the u joints and the joints in the half shafts?
You mentioned drive shaft. Has any one checked the u joints and the joints in the half shafts?
Thread Starter
5th Gear
Joined: May 2011
Posts: 5
Likes: 0
No mods done. Dad's a fan of completely stock... go figure...
u joints were replaced about 10k miles ago
joints in the half shafts unchecked...
have NOT tried 3k in neutral yet, I'll give that a crack asap
u joints were replaced about 10k miles ago
joints in the half shafts unchecked...
have NOT tried 3k in neutral yet, I'll give that a crack asap
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Melting Slicks
Joined: Jan 2009
Posts: 3,482
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From: folsom california
if the cars not moving (in neutral or park) does the vibration manifest itself ? if yes I would say its engine related ?
can you SECURELY jackup and block the car but allow the rear wheels to rotate and if the vibration then persists, its driveline or rear wheel balance / out of round related ? is there a (smog ?) shop nearby with a set of rollers you could put the car on and attempt this same test under load ?
if the above tests are negative and the vibration only occurs when on the road then its probably front tire / wheel bearing / suspension related.
these things are not always easy to track down, a vibration can travel through a car and be heard or sensed a place distant from its actual source. good luck
can you SECURELY jackup and block the car but allow the rear wheels to rotate and if the vibration then persists, its driveline or rear wheel balance / out of round related ? is there a (smog ?) shop nearby with a set of rollers you could put the car on and attempt this same test under load ?
if the above tests are negative and the vibration only occurs when on the road then its probably front tire / wheel bearing / suspension related.
these things are not always easy to track down, a vibration can travel through a car and be heard or sensed a place distant from its actual source. good luck
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
I'm thinking it's also possible to be transmission related (in that scenario). On automatics doesn't the torque converter still spin with the motor? On sticks, the input shaft still rotates in neutral with the clutch let out. In both cases, there can be balance issues there as well.
Thread Starter
5th Gear
Joined: May 2011
Posts: 5
Likes: 0
Great responses, I really appreciate it!
I could not feel the vibration in neutral.
We do not have a secure way to raise the car, hence why we have to keep taking it into the shop.
Its on its way again to check up on the driveshaft, half shaft and u-joints that were replaced a few thousand miles ago. Also getting a new convertible top for the summer!
Thanks guys I think I know the direction of pursuit. I'll keep updated with the prognosis!
Jesse
I could not feel the vibration in neutral.
We do not have a secure way to raise the car, hence why we have to keep taking it into the shop.
Its on its way again to check up on the driveshaft, half shaft and u-joints that were replaced a few thousand miles ago. Also getting a new convertible top for the summer!
Thanks guys I think I know the direction of pursuit. I'll keep updated with the prognosis!
Jesse