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Change rear shocks on a Chevy Blazer or GMC Jimmy.

Suspension Repairs:

Replacing Rear Shocks On A
1999 GMC Jimmy or Chevy Blazer

May Also Apply To S10 Pickup and GMC Compact Pickups

 
In This Article:
The upper mounting bolts are removed with a socket and long extension. The nut is removed from the lower bolt and the bolt driven out. The shock absorber is removed.
Related Articles:
Skill Level:
3 (Intermediate)
Time Taken:
2+ Hours
Author:
Bruce W. Maki, Editor
Project Date:
September 2011
By Bruce W. Maki, Editor
By HammerZone.com Staff
Start >>

How To Diagnose Worn-Out Shocks:

1. When there is oil seepage on the outside of the shock. This appears as a wet spot, usually with dust sticking to it.

2. When the vehicle fails the "bounce test": Push repeatedly on the bumper with your foot to get the car bouncing up and down, then stop pushing. The vehicle should bounce one-and-a-half times and stop. Any more bouncing means the shocks are worn out.

BUT... A vehicle can pass the bounce test and still have worn shocks. This 1999 GMC Jimmy was that way.

3. When the vehicle has to much "body roll" when turning, or seems to bounce up and down too much on humps and bumps. This was my situation. On the freeway, I'd hit a slight hump and feel the car bounce two or three times. It was a subtle effect that some drivers might not notice.

 

Changing Shock Absorbers:

First, the vehicle must be raised and supported safely.

GMC Jimmy raised on jacks with wheels removed.

I raised the car with a large floor jack and placed jack stands under the rear axle just a few inches inboard from the leaf springs.

I lowered the spare tire and set it aside. This gave me more elbow room, and a chance to lubricate the little winch that lowers and raises the spare tire.

 

 

This is the right rear shock absorber. The lower end is easy to reach.

Original rear shocks on Jimmy / Blazer.
 

 

Upper mounting bolts on rear shock absorber, Chevy Blazer or GMC Jimmy.

The upper end is held to the frame with two bolts (red arrows).

(This picture is looking almost straight up.)

I sprayed some penetrating oil on the tips of the bolts where they protrude above the frame, and also on the nut at the lower end.

 

 

I used a 13mm socket, a long extension, and an impact wrench to remove the upper bolts.

They came out without a fight.

Removing upper shock bolts with socket and long extension.
 

 

Removing nut from lower mounting bolt on rear shocks, GM truck.

On the lower bolt, I used a 21mm impact socket on the nut and a 21mm wrench to hold the bolt head.

I later discovered that one of my 13/16" wrenches would fit on the bolt head.

 

 

A Simple Step... NOT!

I used a hammer to tap out the bolt (red arrow).

Actually, I attempted to tap out the bolt. I could turn the bolt head a little, but it felt "springy". The bolt had rusted onto the metal sleeve inside the rubber grommet at the bottom end of the shock, so I had to spray penetrating oil all over the area while working the bolt head back and forth. Eventually I was able to rotate the bolt completely and drive the bolt out, but I had to thread the nut onto the end of the bolt to prevent damage to the threads while hammering.

Driving out lower shock bolt  at rear of car, not always easy.
 

 

Trouble With Removing The Lower Shock Bolts:

While removing the lower bolt on the other shock, I began to realize why so many mechanics use a torch to simply cut away the bolts when replacing shock absorbers.

Removing the nut on the lower bolts was easy with an impact wrench. You'd think that the bolt would just slide out of the hole, but you'd be wrong. The lower bolt on the driver's side rear shock was badly rusted to the metal sleeve inside the rubber grommet. Using an impact wrench on the bolt to break it free was pointless, because the rubber grommet just absorbed all the impact. Of course, I sprayed a lot of penetrating oil all over the bolt area, but that made little difference. I threaded the nut onto the end of the bolt and pounded like mad on it with a 3 pound sledge hammer, but all I accomplished was bending the metal mounting ears on the frame.

So I used a reciprocating saw (i.e. Sawzall) to cut the outer steel ring around the rubber grommet in two places. I was able to remove the shock while leaving the grommet and inner steel tube still in place. I wanted to expose the inner metal tube and hold it with a pipe wrench or Vise-Grips while turning the bolt. I continued with the Sawzall and made several cuts in the rubber (not easy) and then tried pulling away chunks of the grommet, but the rubber was so well-bonded to the inner metal tube that only small bits came off. At this point I had been fighting this bitch for about 2 hours.

I got about one-third of the rubber hacked away before I decided to use a propane torch to burn away the rubber. That was exciting! The rubber caught fire easily, and the flame didn't get too big, but the fuel tank is nearby and the fuel filler tube was directly above the flame. And I had just filled up with gas earlier that day. While the rubber burned, I used a screwdriver to scrape the burned surface material off the grommet. Of course, I kept a big bottle of water nearby, but a fire extinguisher would've been smarter.

Eventually I burned away enough rubber so that part of that inner metal tube was exposed. I used a small pipe wrench to grab the tube, but I was not able to hold it. Vise-Grips were no better. Next, I heated up the tube with a tiny oxygen-Mapp gas torch, which has the ability to (sometimes) get steel red hot. As the metal cooled I soaked it with penetrating oil, then I hammered on the end of the bolt. It didn't move.

The next day I decided it was time to buy a pneumatic air hammer. I have often wanted an air hammer, but have always gotten by without one. I went to Sears and bought an air hammer for $40 and a set of four tips for $25. With the nut threaded onto the end of the bolt to keep the tapered punch tip from sliding off, I pulled the trigger and the bolt just eased itself out in about 10 seconds. Actually, it took longer because after a couple of seconds of hammering, the car horn started beeping, and the alarm wasn't even set. So I had to crawl out, put the key in the ignition and turn it to stop the alarm.

The air hammer really saved the day on this job. It was definitely worth the 65 bucks I paid.

 

Gas-charged shocks will extend when unbolted from the vehicle.

Once the last bolt was removed, the lower end of the shock extended itself downwards. This happens with gas-charged shock absorbers.

 

 

Replacement Shock Absorbers:

I bought four KYB shocks for about $140. Note how there is a strap around the shock to keep it from expanding while in the box. It's okay to remove the strap now, or later after one end is fastened to the car.

New KYB shock absorbers.
 

 

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Installing New Shocks
Fastening lower end of new rear shocks, GM truck.

The new KYB shock was a little narrower at the lower mounting ear, so I placed a 1/2" washer between the mounting ear and the vehicle frame.

I tightened the nut and bolt snug, then I backed off the nut a half-turn so the shock could pivot while I fastened the top.

I applied Syl-Glyde brake lubricant (a silicone-based grease) to all of the bolt threads before assembly, to deter rust and make removal easier.

 

 

I also smeared a dab of brake lube around the inside of the inner metal tube (using a cotton swab), to prevent the bolt from siezing up inside the shock again.

 

 
 
 
 
 
 
 
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I cut the strap and the shock expanded until it hit the frame above.

I installed the two bolts that secure the top of the shock.

TIP: Before cutting the strap, thread the outboard bolt into its hole a few turns, then cut the strap and slide the shock mounting bar under the bolt. Then install the inboard bolt.

Top end of new rear shock.
 

 

New rear shock absorber in GM compact truck.

The completed shock absorber installation.

A pair of shocks can be replaced in about half an hour... if everything cooperates and the fasteners don't give you trouble. But with older cars you can never depend on things going well.

 


More Info:
Tools Used:
  • Impact Wrench
  • 1/2" Drive Socket Extensions
  • Impact Sockets: 13mm, 21mm
  • Combination Wrenches, 21mm and/or 13/16"
  • Ball Pein Hammer
  • Air Hammer with Tapered Punch Tip
Materials Used:
  • Aftermarket Shock Absorbers (2)
  • Penetrating Oil
  • Brake Grease
 
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