Car Raises and Lowers!!
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Joined: Sep 2009
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From: Suffolk County New York
St. Jude Donor '10, '14
Car Raises and Lowers!!
Hello all
I have ventured back to the Vette world with a new to me 1982 base model. I have been fixing valve covers leaks and transmission leaks for the past few days, which I expected.
Here is my question. With the car running with my foot on the brake, when I place the Transmission in reverse, the back of the car raises significantly. When I put it in Drive, with my foot still on the brake, without moving, the car lowers back to its beginning stance. Normal? If not, where do I start looking. Thank you.
I have ventured back to the Vette world with a new to me 1982 base model. I have been fixing valve covers leaks and transmission leaks for the past few days, which I expected.
Here is my question. With the car running with my foot on the brake, when I place the Transmission in reverse, the back of the car raises significantly. When I put it in Drive, with my foot still on the brake, without moving, the car lowers back to its beginning stance. Normal? If not, where do I start looking. Thank you.
Last edited by PARANORMAL; Feb 7, 2021 at 04:04 PM.
Thread Starter
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From: Suffolk County New York
St. Jude Donor '10, '14
2026 Loser of the Year
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From: New Or-leens Loo-z-anna
Rookie guess:
It's possible the large rubber cushion at the lower front part of the differential is loose or flattened so much it is allowing the differential to cause the rear end to raise/lower.
What is your idle RPM with the car in gear/foot on brake? Too much idle RPM can compound the problem.
Is the rear spring and both shocks in good shape?
It's possible the large rubber cushion at the lower front part of the differential is loose or flattened so much it is allowing the differential to cause the rear end to raise/lower.
What is your idle RPM with the car in gear/foot on brake? Too much idle RPM can compound the problem.
Is the rear spring and both shocks in good shape?
Last edited by doorgunner; Feb 7, 2021 at 05:22 PM.
Thread Starter
SUPPORT AUTISM
Joined: Sep 2009
Posts: 1,954
Likes: 48
From: Suffolk County New York
St. Jude Donor '10, '14
Rookie guess:
It's possible the large rubber cushion at the lower front part of the differential is loose or flattened so much it is allowing the differential to cause the rear end to raise/lower.
What is your idle RPM with the car in gear/foot on brake? Too much idle RPM can compound the problem.
Is the rear spring and both shocks in good shape?
It's possible the large rubber cushion at the lower front part of the differential is loose or flattened so much it is allowing the differential to cause the rear end to raise/lower.
What is your idle RPM with the car in gear/foot on brake? Too much idle RPM can compound the problem.
Is the rear spring and both shocks in good shape?
Thread Starter
SUPPORT AUTISM
Joined: Sep 2009
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From: Suffolk County New York
St. Jude Donor '10, '14
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Its just the torque of your motor trying to turn your rear axle with the brakes on. Its just a soft spring that is more for comfort than performance.
Last edited by Rescue Rogers; Feb 8, 2021 at 08:06 AM.
Race Director
Joined: Mar 2016
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From: Napa Valley California
I would be on the safe side and check the front differential bushing as Doorgunner suggested.
When I purchased my 73 it had a slight clunk and the rear lifted slightly higher than I thought it should when shifting into reverse.
After I purchased it I had a safety inspection done on the car, and they told me it was something common when the diff bushing was warn.
They installed a new one for me and it greatly improved the reverse squat and no more clunk.
The one they removed was hard, cracked and deteriorated.
When I purchased my 73 it had a slight clunk and the rear lifted slightly higher than I thought it should when shifting into reverse.
After I purchased it I had a safety inspection done on the car, and they told me it was something common when the diff bushing was warn.
They installed a new one for me and it greatly improved the reverse squat and no more clunk.
The one they removed was hard, cracked and deteriorated.
Drifting
Joined: May 2018
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From: Brampton, Ontario Canada
Except for the 49 year old part. I'm thinking 39 
Last edited by How Are You; Feb 8, 2021 at 08:27 PM.
Team Owner
Joined: Jan 2006
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From: Crossville TN
What is the idle speed of your engine, once it has fully warmed up? If the idle speed is significantly higher than GM specifications, that could cause the symptoms you are observing. And, if that is the case, there is some 'issue' with the controls system. Perhaps the ECM is not recognizing that the engine temp has warmed and is maintaining a "choke idle" setting. A defective temp sensor might cause such an issue...but it likely would NOT cause a 'trouble code' to be issued by the ECM (no check engine light would show).
Thread Starter
SUPPORT AUTISM
Joined: Sep 2009
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From: Suffolk County New York
St. Jude Donor '10, '14
What is the idle speed of your engine, once it has fully warmed up? If the idle speed is significantly higher than GM specifications, that could cause the symptoms you are observing. And, if that is the case, there is some 'issue' with the controls system. Perhaps the ECM is not recognizing that the engine temp has warmed and is maintaining a "choke idle" setting. A defective temp sensor might cause such an issue...but it likely would NOT cause a 'trouble code' to be issued by the ECM (no check engine light would show).
Burning Brakes
Joined: Jul 2004
Posts: 1,194
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From: If your not the lead dog the view never changes Boise, Id
Every independent rear suspension, automatic transmission car I have owned does the squat when put into gear. Some more than others but they all did.
Thread Starter
SUPPORT AUTISM
Joined: Sep 2009
Posts: 1,954
Likes: 48
From: Suffolk County New York
St. Jude Donor '10, '14
Rookie guess:
It's possible the large rubber cushion at the lower front part of the differential is loose or flattened so much it is allowing the differential to cause the rear end to raise/lower.
What is your idle RPM with the car in gear/foot on brake? Too much idle RPM can compound the problem.
Is the rear spring and both shocks in good shape?
It's possible the large rubber cushion at the lower front part of the differential is loose or flattened so much it is allowing the differential to cause the rear end to raise/lower.
What is your idle RPM with the car in gear/foot on brake? Too much idle RPM can compound the problem.
Is the rear spring and both shocks in good shape?
What is the idle speed of your engine, once it has fully warmed up? If the idle speed is significantly higher than GM specifications, that could cause the symptoms you are observing. And, if that is the case, there is some 'issue' with the controls system. Perhaps the ECM is not recognizing that the engine temp has warmed and is maintaining a "choke idle" setting. A defective temp sensor might cause such an issue...but it likely would NOT cause a 'trouble code' to be issued by the ECM (no check engine light would show).
Last edited by PARANORMAL; Feb 19, 2021 at 06:52 PM.