What is the annoying rattle sound from the tranny while sitting at idle with the clutch pedal released?

This is a rather common, and annoying problem known as Neutral Gear Rattle (NGR), and is caused primarily by vibration from the uneven-firing interval of the motor (it does, after all, have an odd number of cylinders per bank) being transmitted to the transmission. This frequency also happens to be near one of the gearsetís resonance frequencies, causing a rattle. It disappears with a slightly higher idle RPM, but this is not easy thing to achieve due to the fact that the motorís idle speed is computer-controlled. Dodge has put out a technical service bulletin to address this. But, the TSB to improve the NGR problem will not eliminate NGR. In fact, after 2500 city/hiway miles on the replacement clutch (yes-you get a different, less-aggressive clutch) the problem will slowly return to bother you once again.

The problem has always existed, but roadsters were inherently noisy and have few NGR complaints. The best, real fix is to have your ISM (Idle Speed Motor) re-programmed to idle at 900 RPM. Dealers are technically prohibited from doing this due to the concern of increasing harmful exhaust emissions. Hennessey Motorsports will do it, as well as give a few other benefits, like eliminate the Skip Shift and it's associated light!

A revision to the TSB was received in April 1998 by the dealers that : "basically states draining current fluid and having replaced with 4 quarts of transmission fluid SAE75W (MS-9070) part no. 04874459 and changing tran label to part no. 04275086." Some owners have commented that "it helped, but shifting was definitely a bit stiffer."

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