ACR Rattle Snake Technical Solution Initiative

[ACR Joe]

Time to start a new string; one that specifically focuses on finding a technical solution to the subject problem. I've spoken with many club members over the past several days (owners of all models) and everyone has been extremely helpful and supportive. As previously indicated, I removed the r/s shock/spring assembly from my car yesterday. I disassembled the unit and performed a very careful inspection. While I had hoped that the problem would be evident, it's not.

I am, however, more convinced than ever that the problem relates to the upper shock mount. I am absolutely convinced that the shock valving is not at fault. The noise I get is a heavy metallic rattling sound that is telegraphed directly into the frame. It's just too heavy a sound to be a shock valve.

Here's one area I'm focusing on right now. The bolt that secures the upper shock mount is about 3.5" long excluding the head. It has threads that are about 1.75" in length and as a result, one of the two conical bushings is resting on the threaded portion of the bolt instead of the shoulder. I measured the diameter of the bolt and it is 0.435" at the shoulder and 0.431 at the threads. That means that there is an additional 0.004" of gap in the threaded area. Enough to cause the rattle? That is the question I hope to answer. The interesting thing is that there is no good reason to have threads that extend that far. I'm guessing it was an off-the-shelf option for Koni.

I plan to work with others in the Viper community to get an opinion on what I believe is happening here. The answer may be as simple as replacing the upper shock mount retaining bolts with newly engineered pieces. Since I already have the stock parts disassembled, I suppose I could serve as guinea pig and supply the parts for measurement and testing.

Stay tuned, we're going to get this thing figured out.

 

[GTS Dean]

OK Joe,

Just for reference - here are photos of the standard Viper rear shock eye and fastener. As you can see, this bolt is also stepped diameter along its length, with the threads loaded in shear. Good engineering practice shys away from this, but unless you drop the car on its wheels from a crane 300 ft up, you probably will not ever fail the bolt thru the thread root.

Dean

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[Ulysses]

I have to back up what Dean is saying. I have seen this done on aftermarket 4x4 shocks as well where the sleeve is bigger than the bolt in diameter. Once that nut is tightened down, you won't get any movement, even after taking whoop de do's at high speeds and getting air. I've even taken washboard ruts on dirt roads at high speeds with this kind of a setup and no shock rattle.

 

[ACR Joe]

I fully agree with Dean as well, however, the ACR shock setup is completely different. I fail to understand why the mounting bolt has so much thread, although for the base suspension, I believe it is irrelevant. Since the ACR does not have a serrated bushing to clamp the saddle, the mounting bolt diameter becomes much more critical.

Anyone out there with the ability to photograph the ACR shock/spring setup and post the photos on the board? That would really be helpful. If Jerry Scott had a ACR, we would really be in business.

 

[ACR Joe]

Just wanted to update all interested parties (ACRers) that progress continues on this end. I am awaiting gauge plugs from George Ciamillo at MGW. A gauge plug is a precision measuring device for determining inside dimensions. In this case, it will enable me to accurately measure the maximum shoulder size that can be used. As this will be a machined component, we might as well make it as precise as possible. You may recall I had specified 0.4375, but will evaluate even tighter tolerances; perhaps as much as 0.4400.

In case anyone thought this initiative was losing momentum .... not!

Stay tuned ........



These pluyou

 

[Vipergtsbob]

Joe, keep up the good R & D work. Glad that George from MGW was able to offer some assistance. I have completed my first draft of our letter to Dodge. I also met with our new VCA national president Tony Estes at the Barrett Jackson auction this past Saturday. Tony gave me some hints for the letter and I hope to post the draft in the next couple of days;(I am still awaiting responses from ACR owners who wish to join us)
Keep in touch.
Bob Carroll
[email protected]

 

[Viperrick]

Bob did you sign off with a 2000 ACR Black with Cognac interior? I thought ACR's only came with black interior.

 

[Vipergtsbob]

Rick, you are right. ACRs could not be ordered with the Cognac interior from the factory. However, the whole interior set is available Via Mopar and I purchased same for an extremely fair price and upon delivery had the new interior installed. (I almost foolishly sold the original black interior and could have recouped a good chunk of the cost of the cognac; however a number or our VCA bretheren convinced me to retain same as future resale would be enhanced by having both interiors available.) I realize this was an act of eccentric behavior, but I really like the baseball glove interior, especially with the Black/silver exterior. BTW, I was offered 90,000. for the car at a recent car show I attended by a person I know to be a real buyer. He liked the uniqueness of the only Cognac ACR. So you never know. PS I ain't sellen'...

Thanks for the inquiry.
Bob CArroll
[email protected]