Idle Chatter

David S.
Update by David S. Wallens to the Mazda Miata project car
Apr 19, 2002

We have put about 800 miles on our Kaaz limited-slip differential, and the noise level is (fortunately) dropping. Maybe we’re getting old, but the chatter started to get on our nerves. Right now it only slightly chatters in slow, tight turns. At speed and during most driving situations, the unit is pretty unnoticeable. In following the Kaaz break-in instructions, we recently refilled our differential fluid, going to Mobil 1 Synthetic Gear Lubricant. Almost immediately, this 75W-90 gear lube quieted our differential. Possibly the best $4.97 we have spent on the car to date.

In other Miata news, we recently used the car to do a little scientific testing: heavy wheels vs. light ones. Do heavier wheels really hurt performance as much as people say? We now have some concrete answers, and full details will appear in the magazine soon.

In an effort to totally silence our limited-slip differential’s chatter, we changed the fluid once again. On the advice of a technical-inspector-type friend, we refilled the differential housing with Valvoline’s petroleum-based gear lube mixed with a few ounces of GM’s limited-slip additive. The result? A smooth, silent differential.

We’re also looking at some new springs, and Ground Control’s Jay Morris ( is working on some new rates for us.

This past weekend, the car got a workout with the Martin Sports Car Club, and independent, Orlando-based organization made possible by the generosity of the Lockheed Martin Corporation. Their rules are similar to those by the SCCA, but different at the same time. (It’s almost like autocrossing in a similar, parallel universe.)

Our car was placed in their E Prepared class, and we scored a first-place finish for our efforts. (Fortunately for us, the 1.8-liter Miatas are in a different class.) For more information on this club, check out

Due to new security measures put in place, the club can no longer autocross on the Lockheed Martin grounds. Therefore, they’re running events at the Brevard County Community College campus in Palm Bay, Fla., site of the GRM Challenge events. Their most recent event featured a flowing, 55-second course featuring two high-speed straights.

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