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Many cars have more than one rev limiter. The one most people are familiar with simply stops the engine from reving very far past redline. That's because over reving an engine can cause valve float, bearing damage, and possibly cause a rod or rod bolt to break (which 600 Yamahas were famous for). Sometimes a second rev limiter is installed in cars with an automatic transmission and it only works while the car is either in neutral or park (park is actually neutral with a device that stops the car from rolling).
Racing the engine in a car with an automatic transmission can be a bad thing. This page will explain why. There may be a good reason for racing an engine while in neutral, but the risk may outweigh the benefit, if any.
Caveat: I've never rebuilt an automatic transmission and I have no predilection to learn. A "proper" transmission rebuild requires very expensive, transmission specific tools that I have no intention of buying. I've done clutches in manual transmissions and replaced front and rear main seals, but that's about it. I have very little first hand experience with slush boxes.
That said, when an engine turns, the torque converter turns. The torque converter is attached to the transmission's
input shaft. When the input shaft of an automatic transmission turns, at least one planetary gearset is turning. For
each planetary gearset that's turning, at least one small sun gear, possibly one large sun gear, several inner
planet gears, outer planet gears (if it's a compound planetary gearset), and a ring gear are moving. Memorizing all
these gear types isn't important. The things to come away from this with are that gears in the transmission are
turning, AND moving parts require lubricant. The faster they move, the more lubricant they require.
There are obviously differences between a manual transmission and an automatic. One difference is in the lubrication system. In a manual transmission, the oil follows the same route, or path, regardless as to which gear it's in. In an automatic transmission, automatic transmission fluid (ATF) doesn't always follow the same path. ATF typically flows from the pan, through the filter, to the pump. The oil pump in a transmission is driven by the pump drive hub of the torque converter. After the fluid leaves the pump, the flow of ATF is dictated by a part called the valve body. The first stop for the ATF in a valve body is the pressure regulator valve. A pressure regulator valve is one of the few parts I know of that exist in all automatic transmissions. However, sometimes that valve is physically separate from the valve body. At any rate, after leaving the regulator valve the fluid goes to one or more of the other valves in the valve body. The job of valve body is to regulate (hence the regulator valve) and direct fluid (the purpose of the other valves in a valve body). Where does the fluid go? Hopefully to those moving parts that require lubricant.
The valve body, which is in charge of directing fluid, knows whether or not the transmission is in drive, or whether it's in neutral. It is entirely possible that moving parts which ordinarily receive "x" amount of ATF at five thousand RPM while in drive, only see a fraction of that amount while in neutral. If so, those parts which are supposed to be bathed in ATF while spinning at a high rate, may be severely damaged by a lack of ATF. The problems associated with an automatic transmission experiencing high RPMs while in neutral may be why some manufacturers have implemented a secondary rev limiter.
If you know the ATF flow schematic of your automatic transmission, then you know if reving the engine high enough to make dogs howl is harmful. Not knowing and reving it, is not something I'd recommend.