Z06 Corvette

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2004 Z06 Rear Shock Upgrade


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The 2001 Z06 suffers from a twitchiness under hard acceleration from a standing start. According to Corvette chassis engineers this is due to jounce shock valving which is too stiff, coupled with jounce bumpers which are too tall. This inhibits weight transfer to the rear tires and produces the brief but attention grabbing side to side movement of the rear end.

The solution to this problem was introduced on the 2002 Z06 and reached its pinnacle on the 2004 Z06 with much improved shock damping curves. So I decided to replace my OEM 2001 rear shocks with the 2004 parts which carry GM part number 10339945 (AC Delco part number 540-137). Price from my Chevy dealer was $135.00 each. The 2004 front shocks carry GM part number 10339944.

What follows is a step-by-step illustration of the installation process with photos for anyone who wants to go the same route. Where appropriate I'll provide photos that clarify a topic. I'll also point out the errors posted on other Corvette sites with respect to bolt torque, etc.

Here is a list of parts that you will need.

Rear shock absorbers (2) (GM part number 10339945, AC Delco part number 540-137 )

You will need a fair amount of tools for this upgrade. Here is a list.

4 jack stands
1 very low jack

3/4-inch 1/2-inch drive socket (lug nuts)

24mm sockets (2) (Lower shock mount bolt and nut) 13mm socket (upper shock mount bolts) 18mm box wrench (tie rod end link nuts)
13mm ratcheting box wrench (upper shock mount bolts) 6mm metric hex key (tie-rod mounting stud)

18-inch 1/2 inch drive breaker bar
15-inch 1/2 inch drive breaker bar
3/8-inch drive air ratchet (optional but recommended)
3/8-inch drive ratchet
1/2-inch drive ratchet

1/2-inch drive torque wrench (click type is better)

The first step in the process is jacking the car. In their infinite wisdom, the Chevrolet engineers made certain that this is harder than it has to be and should be. It is not possible to use the jacking points and place jack stands at the jack points, unless you can make the car levitate while you remove the jack and insert the jack stand.

There are various techniques, none very attractive, and I choose to jack up the front first. Slide a very low jack under the air dam and position it in the center of the front cross member (see arrow). Jack the car and place jack stands as far out on the front cross member as possible.

Next raise the rear by placing the jack under the center of the rear cross member. I place the jack stands on each side of the jack point, then lower the car onto the jack stands. I place a two-by-four under the cross member so there is no metal-to-metal contact.

Once you have the car in the air it's time to remove the rear wheels. After the wheels are removed you can remove the old shock.

Start by loosening the lower shock mount bolt. You will need two 24mm sockets and a ratchet and a breaker bar (or two breaker bars). Use one on the bolt-head and one on the nut as you loosen either. The point is to get the nut off the bolt and slide the bolt out of the lower control arm mounting bushing. This bolt is installed with 162 ft-lb of torque so removing it will take a few grunts. It helps to put a jack under the lower control arm and raise it an inch or two to take the tension off the lower mounting bolt.

Next loosen and remove the upper shock mount bolts with a 13mm socket mounted on the end of a six inch extension, using a ratchet.

You will need to disconnect the tie-rod end in order to get the old shock out and the new one in. This requires a 6mm hex key to hold the stud stationary and an 18mm box wrench to loosen the nut. The shop manual indicates you need a ball joint separator to get the tie-rod end out of the knuckle but mine just slid out when the nut was removed. Here is the tie-rod end after removal from the knuckle.

Slide the new shock into position and lower or raise the jack until you can slide the bolt back into the mounting hole easily.

Torque the upper mounting bolts to 22 ft-lb and the lower mounting bolt to a whopping 162 ft-lb.

Reinstall the tie-rod end. Here is a shot of the new shock mounted and the tie-rod end reconnected. When you're all done you can reinstall the wheel. Note that I had previously installed stainless steel brake lines, aluminum stabilizer bar end links, polyurethane stabilizer bar bushings, and drilled and slotted GM Durastop rotors (which I replaced with Baer Decelarotors soon after).

Reinstall the wheel and torque the lug nuts to 140 ft-lbs (per the Corvette Shop Manual page 3-98).

This job takes about two hours.


Doing business with AJ-USA aka Direct Source Outlet in San Diego, CA.


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Creation Date: Tuesday, July 3, 2007
Last Modified: Tuesday, July 3, 2007
Copyright Ray Smith, 2007

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