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There is a service bullitin for some 90 and 91 convertibles that instructs the dealer to REMOVE (2) "mass dampers" from the frame near the rear bumper. The bullitin says they weigh 20 pounds each. Has anybody found these on their car? If so what does a "mass damper" look like? It weighs as much as a bowling ball!

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YES, they are commonly referred to as "Cock-Tail shakers"

They are mounted to the rear bumper bracket, with a 1/4" plate bracket. They are a rectangular-cylinder shape, and full of shot. They were added to balance the front/rear weight distribution, to eliminate harmonic shaking of the car on uneven pavement, some call "Cowl shake". when the shaking occurs, it is not the "Cowl" but rather the rear of the body shaking, hence the cocktail shakers.

OldBuickMan would have more inside info on this subject, as his division, (sales) is who ultimately had to deal with it.

I'd be interested in a pair of these units, for research purposes, if found. George Madsen has a pair, maybe he could post some pix.

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Randy, you would have thought that GM would have learned a lesson from the 1982 to 1985 Riviera convertibles that were produced without any frame re-inforcement. I drove several of them and not only did the cowl shake but so did the doors when you would close them. I had a chance to drive a riviera convertible that had been converted by Hess and Eisenhardt out of Cincy,Ohio. They reinforced the frame and also had a thick headliner that our factory unit didn't have. It was like night and day difference driving the two cars. there was no cowl shake with the Hess and Eisenhardt car and the doors lined up perfect. It was also quieter inside as well.At one of our announcement meetings I had a chance to talk to our chief engineer on why they wouldn,t beef up the chassis on the Reatta convertible and he said because the car was going to go away in 1991,the corporation didn't want to spend the money on the car. You would have thought management would have learned a lesson from the Riviera convertible. Frank

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The weights were only installed on the '91 convertibles and not the '90s. It is my understanding there was a recall from GM to remove them from the '91 convertibles although some still exist.

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Allow me to try and clarify the above.

There was first a "fix" added to all 1991 convertible that added a 10mm shim at the outside ends of the rear leaf spring. This was part #1648853 and Dealer Service Bulletin 91-10-26 dated July '91 suggested that it be added to 1990 convertibles to adjust rear standing height.

For 1991, the same bullitin gives instructions for adding the rear "damper" #22112267 left and # 22112268 right, see picture. As you can see, this was bolted to the rear bumper energy absorber. A later service bulletin told the dealer to remove them. Since this bulletin was dated July '91 it could be assumed that none of these were added to production cars at the factory, since convertible production ended in March '91.

Lastly, the "cocktail" shakers were never added either at the factory or as a fix to the Reatta. First there was no room for them. I have a poor picture attached of a cocktail shaker in the front of a Corvair convertible.

My rough guess is they were roughly 5" in diameter and 10" long....try and find space for that in your Reatta.

There are stories that Reatta engineering tried the cocktail shakers, but they were never put in production convertibles. PS They were called cocktail shakers because they looked like cocktail shakers, they were two deep drawn steel shells welded together in the middle.

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post-30596-143137961641_thumb.jpg

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This is a photo of the right front "damper" on a 1965 Corvair convertible. it is bolted to the wheel well bead.

The roundy thing to the left is the headlight bucket.

The actual measurements of the basic damper is 9 1/4 X 4 1/2

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Some aircraft have the battery mounted in the back. This is done to adjust the Center of Gravity without increasing weight. I wonder if the engineers at GM considered moving the battery to the trunk of the Reatta at any point. That sure sounds like a better idea than "mass dampers" with useless lead shot. I have a suggestion to all convertible drivers. To reduce "cowl shake"; leave your bowling bag in the left rear of your trunk and tour wife's bowling bag in the right rear of the trunk. Just remember to get to the bowling alley early to warm up your balls in the winter!

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