The reason to connect a ground cable to the gearbox is actually to ground the starter that is mounted in the same housing/near to the gearbox.
Most cars already has a stock ground to the starter/gearbox.
Additional ground to the gearbox, even it's an auto-transmission, is not necessary.
Same goes to the intake manifold, even with fly-by-wire throttle. The reason for some car to have a cable connecting the intake manifold to the firewall, is to ground the firewall. In other words: - to make the body and engine electrically unity.
In some cases, such as V6 engines, a cable is connected to the intake manifold of the hidden engine bank, since reaching a suitable point on the hidden bank is technically difficult.
Any seller can come out with many theories to justify a layout with more points. not many will tell you what you really need.
Most cars already has a stock ground to the starter/gearbox.
Additional ground to the gearbox, even it's an auto-transmission, is not necessary.
Same goes to the intake manifold, even with fly-by-wire throttle. The reason for some car to have a cable connecting the intake manifold to the firewall, is to ground the firewall. In other words: - to make the body and engine electrically unity.
In some cases, such as V6 engines, a cable is connected to the intake manifold of the hidden engine bank, since reaching a suitable point on the hidden bank is technically difficult.
Any seller can come out with many theories to justify a layout with more points. not many will tell you what you really need.
