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How Do You Replace C4 Shocks

Old 01-30-2011, 08:54 PM
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Jim Nichols
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Default How Do You Replace C4 Shocks

Does anyone have a link to how to replace the shocks on a 91 Coupe? I have checked the tech section without finding what I am looking for. Appreciate any help.
Old 01-30-2011, 09:09 PM
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It's pretty straight forward unless you have the adjustables, than it's just $$$$. Was there a specific problem you ran into?
Old 01-30-2011, 09:28 PM
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You need to access the top bolt of the rears under the carpet.



BTW use lots of PB blaster on those bolts.
Old 01-30-2011, 09:29 PM
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This will get you started

http://www.corvette-guru.com/uploads...rontShocks.pdf
Old 01-30-2011, 09:35 PM
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The Factory Service Manual is your friend.

Just my respectful opinion...if you're asking such a basic question, I highly recommend you take the car to a shop.
Old 01-30-2011, 09:37 PM
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zr1fred
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I think the 91 uses a bracket, adapter, plate (pick one) that bolts on to the top of the rear shock and then bolts onto/into the frame with two 13mm bolts.
Old 01-30-2011, 09:37 PM
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Originally Posted by JrRifleCoach


You need to access the top bolt of the rears under the carpet.



BTW use lots of PB blaster on those bolts.
There are no bolts you access by removing the carpet. You remove the two bolts that secure the mounting plate to the frame via the wheel well.
Old 01-30-2011, 09:53 PM
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Originally Posted by 96GS#007
There are no bolts you access by removing the carpet. You remove the two bolts that secure the mounting plate to the frame via the wheel well.
Sorry. Thought the late C4's had a single nut on the top. Read somewheres where the top nut was easier to access from the top?
Maybe it was a mod...

Old 01-30-2011, 11:39 PM
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Originally Posted by JrRifleCoach
Sorry. Thought the late C4's had a single nut on the top. Read somewheres where the top nut was easier to access from the top?
Maybe it was a mod...

Only if you use a hole saw and cut thru the top of the frame rail after cutting thru the body. Many people with dedicated track cars will do that in order to more easily adjust Koni adjustable shocks.
Old 01-31-2011, 12:03 AM
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Originally Posted by 96GS#007
Only if you use a hole saw and cut thru the top of the frame rail after cutting thru the body. Many people with dedicated track cars will do that in order to more easily adjust Koni adjustable shocks.
Ok, instead of the one bolt from shock, there are two bolts facing upward holding the bracket remove those two bolts and the bottom part of shock and it comes out. Then you remove that two bolt bracket and put it on your new rear shocks before it goes back in.
Old 01-31-2011, 12:08 AM
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When you look at it, the how-to will be pretty obvious.
Old 01-31-2011, 07:58 AM
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Originally Posted by Frizlefrak
When you look at it, the how-to will be pretty obvious.
Old 01-31-2011, 08:09 AM
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Default 4 hours

If you are handy you can do the complete job in less than 4 hours. If you are not handy have a friend come over that is handy and buy a case of beer and have at it.
Old 01-31-2011, 10:46 AM
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Originally Posted by JrRifleCoach
Sorry. Thought the late C4's had a single nut on the top. Read somewheres where the top nut was easier to access from the top?
Maybe it was a mod...

There were two different upper shock mounts. The early C4's used a bolt that went thru an eye on the top of the shock. There was a saddle-type mount to insert the eye of the shock and the bolt went thru the mount, thrut he eye and a nut on the bolt. Either way, you have to raise the car and remove the rear tires. The large bolt at the bottom does need some effort to remove and the shock has to be slid off the mounting pin.

The later C4's had a separate upper mounting bracket that attached to the shock. Those shocks attached to the bracket similar to the way the front shocks are attatched on the upper part. The bracket then was inserted into a hole on the underside of the frame rail and bolted in with two small bolts.

The front shocks are pretty straight forward, a nut on top of the shock rod for the upper end and two bolts that hold the lower end of the shock to the lower control arm. You don't even need to raise the front of the car to replace the front shocks. The nuts on the lower bolts are easily accessible with a long socket and the nut on the shock rod can be removed with a box-end wrench.
Old 01-31-2011, 01:07 PM
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Originally Posted by RockG
Ok, instead of the one bolt from shock, there are two bolts facing upward holding the bracket remove those two bolts and the bottom part of shock and it comes out. Then you remove that two bolt bracket and put it on your new rear shocks before it goes back in.
It's not hard to do. However, one thing to be aware of, which I just encountered, is that the upper half of the top bushing (that sits up inside the frame rail, can be swollen. On mine I really had to struggle to get it out of the hole in the frame.

Torque on all bolts and top studs is 20 ft lbs. The big nut on the lower rear is torqued to 60 ft lbs.
Old 01-31-2011, 01:58 PM
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Originally Posted by dwblindref
If you are handy you can do the complete job in less than 4 hours. If you are not handy have a friend come over that is handy and buy a case of beer and have at it.
Plan on doing very little wrenching and a lot of drinking. Start an hour before superbowl and still not miss kickoff.
Old 01-31-2011, 02:24 PM
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Originally Posted by 92ragtop
It's not hard to do. However, one thing to be aware of, which I just encountered, is that the upper half of the top bushing (that sits up inside the frame rail, can be swollen. On mine I really had to struggle to get it out of the hole in the frame.

Torque on all bolts and top studs is 20 ft lbs. The big nut on the lower rear is torqued to 60 ft lbs.
When the lower shock nut on the rear suspension is tightened, the car has to be on the ground at ride height. Snug the nut up and roll the car back and forth a couple times so the suspension settles and then tighten to the spec.

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To How Do You Replace C4 Shocks

Old 01-31-2011, 03:59 PM
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Joe B.
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Shock replacement is pretty straightforward, right, but here's a small dilemma. In general the top nut should be tightened to expand the bushing out to the dia. of the washer. The previous post said 20 ft. lbs. on the nut. Replacement washers are a harder urethane than the stock rubber ones so maybe 20 ft.lbs. isn't enough to properly expand the bushing. Comment? One other point, the stock bushings have a nice male female arrangement to them to keep them centered on the stud. Replacements will probably be the generic donut type. If the stockers are in perfect condition, as mine were, can or should they be reused?
Old 03-10-2011, 07:33 PM
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Default 94 fx3

Is this the same on the rear with FX3 actuators? Remove the two bolts and it all slides down out of the hole? I seen nothing when I pulled up my carpet.
Old 03-10-2011, 08:12 PM
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Originally Posted by Rocket-J
Is this the same on the rear with FX3 actuators? Remove the two bolts and it all slides down out of the hole? I seen nothing when I pulled up my carpet.
Yup. You unbolt the plate and then pull the shock assembly out of the hole in the frame. If the bushings are swollen, you may need to use some persuasion.

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