Anonymous asked in Cars & TransportationCar Audio · 1 decade ago

Big Three Upgrade please help?

Alright so I wanna run a system of about 1500rms. I know that I'll need to do the big three upgrade, but i cant figure it out. I have a 2009 toyota tacoma. I looked under the hood and found the battery to chassis ground wire, engine block to ground wire, but i followed the stock wire from the battery positive terminal, hoping that it would just lead directly to the alternator, but it doesnt. It goes from the battery terminal down under the engine where it connects to some sort of tube like thing.

If someone could help me out on how to wire up the positive wire in the big three upgrade on a 2009 toyota tacoma that would be great.

3 Answers

  • 1 decade ago
    Favorite Answer


    Performing a "Big 3" upgrade on your vehicle is one way to improve the electrical system performance and its ability to supply power to your audio system. This upgrade will help any vehicle using an after-market amplified stereo system, and most certainly should be performed on any vehicle after a high-output alternator is installed.

    Definition: the "Big Three" upgrade means improving the current capacity of three cables: 1) alternator positive to battery positive, 2) battery negative to chassis, and 3) engine ground to chassis. Some people replace the factory wiring; others add additional cables to the factory wiring. This instruction is to add cables to existing OEM wiring.

    Parts and Tools

    • Sufficient length of high-strand count high capacity power cable.

    - The length required differs for every vehicle. You can measure the length of the existing cables and buy the same length, or contact your dealer or a mechanic and ask, or sometimes you can look it up in a manufacturer's wiring book, or guess. If you guess, make sure you over-estimate and buy too much.

    - High strand count cable is more flexible and more reliable than low-strand count cable. Never use solid-core wire in a moving vehicle as it will eventually break.

    - The gauge of wire you need depends on the total current draw of your audio system, and/or the current generating capacity of your alternator. Never use smaller cable that you used to power your amps; never use smaller cable than what already exists in your vehicle; never use smaller cable than the generating capacity of your alternator; never use smaller than 4 AWG (it's just not worth the time to use anything smaller); if in doubt, always use higher gauge cable than you think you need. If you look at the Power and Ground charts and your amplifier current draw corresponds to 2 AWG cable, use no smaller than 2 AWG cable, and use 1/0 if you can.

    • 6 ring terminals or lugs of the appropriate size for the cable chosen. Two of these need to be large enough to fit over your battery posts, or appropriately sized to bolt onto your existing battery terminals.

    • 1/2" or 5/8" shrink tubing (or some other form of permanent electrical insulation. Tape is NOT recommended.)

    • Cable ties (plastic zip ties.)

    • Wire cutters large enough to handle the cable you choose.

    • Crimpers large enough to handle the connectors you choose.

    • Soldering iron or gun.

    • Solder.

    • Scotch brite and/or a small wire brush.

    • Heat gun.

    • Safety razor blade (or other tool for stripping cable).

    • Heat gun (if using shrink tubing).

    • Wrenches for removing bolts in your vehicle.


    1. Make sure your engine is completely cool before beginning. Identify the three cables being replaced. Make sure you can reach both ends of all cables. NOTE: the engine block to chassis cable may be between the engine and the transmission, or connected to the transmission and the fire wall, and is often an un-insulated flat braid cable.

    2. Determine the lengths of cable needed to reach between the three locations being upgraded. Be sure you measure with a flexible tape (a tape measure used for sewing works great) and record the total length along the path you intend to install the cable. You do not want your cables to be pulled tight between any two locations as things move and vibrate as you drive. Be sure to include at least 1 inch extra for slack. NOTE: there is no reason to copy the existing wiring layout in your vehicle unless you want to. Also, be sure that the path you choose does not follow or lay across anything that gets hot, like exhaust parts, or anything that must move, like throttle linkage.

    3. Cut your new cable to the three proper lengths. NOTE: some people like to use red cable for positive and black cable for negative. Doing this is completely up to you and is nice, but not necessary. You can use cable with any color insulation you like.

    4. Strip each end of all cables to the proper length for the terminal lugs being used. NOTE: after full insertion into the lug, a small "band" of bare wire is usually seen between the back of the lug and the beginning of the cable insulation.

    5. Begin at any one end and insert the stripped cable into the lug. Make sure it is fully inserted. Crimp the connector to hold the wire in place. NOTE: crimping large cable can be difficult. The intention here is not to make the crimp the sole means of holding the wire, but only to make sure the lug does not slip around during the soldering phase. I do NOT recommend using hammers or pliers or vices to crimp the connector as over-crimping can break the strands of the cable, reducing the current carrying capacity. Do not over-crimp.

    6. You may need to use a vise or some other set of "helping hands" to hold the cable while you solder it. Heat your soldering iron and place it on the connector (on the lug side) barrel. Hold a piece of solder against the tip of the iron and melt the solder into the strands of t

    Source(s): autosound installer.. 12 volts. com
  • 1 decade ago

    The battery positive is going to the starter most likely. There is probably another wire going from the main starter terminal to the alternator. You should get a wiring diagram for that truck. Either buy a Haynes manual, or look it up on line. You need the color codes and a good wiring diagram so you know exactly what wires you need to upgrade.

    Source(s): Experience
  • Anonymous
    1 decade ago

    You dont need to do the big three upgrade at all. I have a scion xb 2006, small car, with a 4 guage power cord hooked to the battery. My amplifier can put out 1200 watts rms, and slams the Kicker 15 inch at 2hms, in my car.

    Really dont need to do this, but there are videos easily explaining how to do it on youtube.

    Source(s): audio pro
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