Thread: The Big 3, Everything You Wanted to Know + DIY

Hey ladies and gents. I’d like to shed some light on the Big 3 wiring upgrade and show some pics of how I did mine plus some of the key grounding points that I resanded to ensure better metal to metal contact. Also, I modified the actual big 3 by doing an alternator rewire (like ZZP’s setup) instead of going directly from the alternator to the battery (you’ll see what I’m talking about later). There are a couple threads on here, but people still seem confused and some people (like myself) prefer to see what’s going on to fully understand what this entails. Some of the information I got from reading:
How to upgrade the Big Three

First, I’m no electrician, I simply took a engineering circuits class in college so I’m not an expert, so any input is appreciated, but having said that it’s not difficult to see that it’s very easy to upgrade the wiring in certain places in the Grand Prixs and hopefully be able to see benefits from these ground and power upgrades. Secondly, this was done on a 97 GT (excuse the Pink, it's my girlfriends cars) so ground points and other locations may be slightly different (remember this year is the exception to every rule). I’d like to list some of the benefits that I’ve noticed from doing this.

-windows take about half the time as before to roll up and down
-brighter interior lights
-cluster and instrument lights are brighter (when they were half way dimmed on the dimmer switch, they could hardly be seen at night, but now the half dim setting is very visible and full brightness is really really bright.
-Fuel pump sounds more confident when key is first turned.
-faster cranking on startup
-starter motor has more umph (the car used to struggle to start if it was started multiple times without letting it run for any good amount of time thus allowing the battery to recharge, but now it starts up perfect every time)
-brighter headlights and they no longer dim when shifter gears or when abs engages.
-better bass from stereo even from stock speakers (those with an amp and sub(s) will see an even bigger benefit)
-Battery recharges quicker (I can’t prove this, but in theory this should be true since the stock wiring from the alternator goes through the wiring harness and then to the battery, but with the way I wired it, the alternator goes start to the battery).
-This also resolved some issues I had with the DIC and radio turning off if the blower fan was turned on a setting higher than 3 when the car was cold and just started up.
-Improved engine performance (again can’t prove this, but ZZP claims that a alternator rewire along will increase MPG, and from my trip back to school tonight I got 26.5 MPG, which is about 1.0 better than previous trips and I had a seized caliper that was half engaged on the entire trip tonight so that didn’t help boost my MPG at all, but more trips should be able to confirm this increase in MPG if there really is any).
-Firmer shifts (not applicable to the 97’s since they are vacuum controlled, but later years should be able to gain firmer shift points, at least from what I’ve read).
-basically all the electronics in the car should now be able to work to their full potential, or at least a heck of a lot better than stock wiring plus X number of years of corrosion and vibration.
-fix stock grounding problems that could result in wierd occurances in the car such as gauges just stop working for a second, HVAC turning off, DIC shutting off, etc

So, what exactly is the big 3?
The big three is three cables either in addition to stock wiring or used to replace the stock wiring, but you can just leave the stock wiring since current will travel through the path of least resistance anyway, so leaving the stock cable won’t hurt a thing.
-Battery negative to chassis ground
-Alternator positive to battery positive (I actually did it to the fuse box, then had a wire from the fuse box go to the battery)
-Engine ground to chassis ground

So now that we can see what upgrading the wiring can do and what exactly the Big 3 is, let’s look at the basics of what should be done and why they should be done. First, when the vehicle is off, the “true” ground (the best ground) is the chassis, so upgrading the wiring from the battery to the chassis will help electronics that are one when the engine is not running. Also, when the engine is not running, all the electronics are getting their power from the battery, so adding a wire from the positive battery terminal to the fuse box should help. However, when the engine is running, the main positive voltage is supplied by the alternator, so anything coming off the alternator will receive the most power being generated. Also, while the vehicle is running, the alternator housing acts as the true ground, and since the housing is bolted to the engine block, the engine block and transmission become the true ground as well. At first I questioned by the third component of the big 3 was necessary, but after realizing the fact that the voltage flow depends on if the engine is running or not, it becomes clear that adding a ground wire from the block/transmission casing to the chassis will help anything that’s grounded to the engine block, especially when the engine isn’t running, but when the engine is running those electronics will have a good ground.
Another reason to do these upgrades is the simple fact that the stock wiring is small and insufficient especially for people with power sapping mods like HIDs, Amp/Subs, a million LEDs, and the 25 port charging station that everyone needs to recharge their laptop, cell phone, and run thier espresso machine all at the same time. The only stock wiring that did seem okay, was the ground from negative battery terminal to the chassis (I believe it was 6 gauge from the looks of it). Also, the ground on the engine had a large cable going to the battery negative terminal, but doesn’t really help matters since the ground for the battery has to also ground the engine ground, again why engine ground straight to chassis will help.


What’s needed to do the Big 3?
-Well, wire of course. I bought 15 feet of 4 gauge wire from knukonceptz.com (about $.89 a foot), but you can get away with about 10 feet of 4 gauge or even bigger if you prefer, but 4 gauge seemed good for my application and was flexible enough to fit into some of the spaces I wanted. Also, the stock alternator on these vehicles only supplies 105amps of power and most 4 gauge wire will allow 100-150 amps of current flow without much resistance due to the length of wire.You can get anything larger than 4 gauge, but just ensure that it’s a quality wire and is flexible so that you can actually route the wire the way you want without causing issue. If you want to do 1/0 gauge wire you should solder the connectors onto the wire. I highly recommend watching Caspers video on how to do this: (Grand Prixs Of North America • View topic - 1/0 Gauge Terminal Connection (Solder))

-Terminal ring connectors (for whatever gauge wire you bought). I used 8 connectors, but only 6 are required to do the big 3.
-Liquid electrical tape or something similar to ensure that the connections do not corrode the first time it rains.
-Zip ties
-Dremel with sanding bit, but any sandpaper will work. Whatever you need to sand off some paint to bare metal.
-Basic tools. Wrenches for removing bolts, wire cutters, crimp tool or solder iron/blow tourch, knife.


THE DIY!!!!!!!!
Okay, now lets get to actually doing this. (the wire I added is white (pearl technically) so pay attention to those wires)

1. I went ahead and disconnected the negative terminal on the battery, followed by the positive connection. Then I loosened the battery tie down bar and removed the battery out of the car (not necessary, but it made things easier to work on. Also, to remove the battery the brace bar will have to be removed, and the washer fluid bottle in the 97-98.

2. I went ahead and removed the nut on the alternator and started to run a wire from the alternator to the fuse box. I took a route along the fire wall to the strut tower, then to the fuse box, but a shorter route can also work if you prefer. Once I figured out the length I wanted, I cut and stripped both ends and added the ring connectors and put liquid electrical tape around the connector. Then just simply unbolt the nut on the fuse box and add the cable.

Wire connected to the alternator. If you use 4ish gauge wire you can still use the stock rubber boot for a slightly cleaner install.

Wire run to the fuse box. You can take a shorter more direct route if you prefer though.

3. Trim the battery terminal cover (the big rubber thing with the bolt in it) so that you can get a ring connector on the bolt. Once installed the bolt should go, upgrade wire connect, stock copper connector, then battery in that order. You could get different terminal bolts at an auto parts store that will allow you to just bolt the new ring connector on without modifying the rubber terminal cover, but I didn’t find this out till afterward.

4. Find a new place to add a chassis ground. I used a bolt underneath the stock ground, which was actually holding down the wiring harness. Then sand down whatever location you choose so that bare sheet metal is exposed. Now, measure out the wire you need and cut according. Again add the ring connectors and add liquid tape or whatever protection you choose. Then place the one ring connector onto the new chassis ground and tighten the bolt down. Then I coated the location in liquid tape to prevent corrosion. Paint or petroleum jelly will also suffice for the job. I then put the other cable into the battery terminal but did not bolt it in since the battery was not in the car. In the mean time I also disconnected the stock battery to chassis ground and sanded down the connector, the bolt and the sheet metal so ensure the stock connector also had good contact.

This is by the stock battery ground. You can see that my added wire runs behind the wiring harness. What you can’t see is that the metal harness tie down bolt is now holding down the new ground wire. The stock ground wire is also very close to this location and is very easy to find if you just pull up on the wiring harness a little.
Sorry for the poor picture, my SLR couldn’t fit into the tight space.

5. Engine block to chassis ground. The engine ground on the transmission is right underneath the Tstat housing. Depending on the model year, different connections will connected to this location (early years 97-00 have one large and 2 smaller ground wire already connected, while 01-03 have a slightly different setup, but that doesn’t really matter anyway, just wanted to share). Take off this nut and pull off the existing ground wire rings. Again sand down the rings a little. Then lay out your wire to get the measurement, cut, and do the same steps as before. Then add you new wire to the engine ground, along with the ground wires that were there before, and tighten the bolt back up. Now locate a good place to add a ground to the chassis. I found one on the bottom of the strut tower by the A/C service port. There was already a smaller wire grounded there, so I just sanded down the sheet metal and added my new ground wire to that location.

Engine ground under the Tstat housing. You can see that I added my new ground wire right on there and ran it out of the way of the hot crossover pipe and the moving fan blades.


This was the chassis ground location I used at the bottom of the driver side strut tower. It was very easy to spot since I don’t have the stock airbox but you could still spot it if you have airbox still installed. (I’m not positive if this location is on all model years, but adding a new ground location isn’t very hard. I just prefer to not drill holes if I don’t need to.)

Excuse the excessive use of zip ties, haha.

6. This is technically part of the big three, but since I added the alternator rewire I did this slightly different. The preferred method is to add a connector from the alternator straight to the positive connection on the battery terminal, but since I did the alternator rewire and wanted a slightly cleaner install, I went ahead and added a wire to the fuse box and then ran that to the battery terminal. As before, run the wire, cut to proper length, and add connector, etc. Then make sure that the nut on the fuse box has either 3 rings (stock, alt wire, alt to batt wire) and tighten the nut, or just 2 wires if you ran the wire directly from the alternator to the battery (this is preferred if you have subs/amp since the current won’t have to run to the fuse box first).

I ran the wire down behind where the battery will sit in order to create a slightly cleaner install. This route will be difficult if using a thicker wire on a 97-98 since the washer fluid tank sits very close to the sides of the strut tower and the upper fender rail.

You can see how the alternator rewire and my route for the battery wire are connected. Again I did this to make for a slightly cleaner install, but taking the direct route is recommended.

7. Then I went ahead and sanded down the stock headlight grounds which are on the front of the car on the main bumper support. There are 2 of them, one on the left side and one on the right side by the hood latch. If you’re performing this on a 04+, the headlight grounds are directly underneath the headlights themselves. This isn’t needed, but should be done while you’re at it. I simply sanded those connections down (ring and sheet metal) and added some liquid electrical tape over the bolt and connection once they were bolted back down. Every little bit helps I guess.

8. First ensure that all of the bolts are tightened down, i.e. any of the chassis grounds, fuse box nut, alternator nut, engine ground nut, etc. Now put the battery back in the car. Bolt down the tie down bracket, then first connect the positive terminal (ensure that the upgraded wire ring is attached to the terminal as well). Then connect the negative terminal, again making sure that you’re new ground wire is also attached.

You can sort of see how I modified the stock terminals and used the stock terminal bolt. As mentioned before you can actually buy a new bolt which allows you to add a ring connector onto the top of it.


9. Put the brace bar and washer fluid bottle back into place and make sure everything is all tight and ready to go and replace the fuse box cover if you removed it.

10. Enjoy the fact that you wired a car better than GM engineers, haha.
The final product…


Hope this helps some of you out there. Again, feel free to contribute to this in any way. If my girlfriend wants to get a sound system I will be redoing the wiring to larger gauge wiring and changing my battery to alternator connection, but till then this will have to do and already it’s made a pretty significant change.
Some other reading that may help:
Grand Prixs Of North America • View topic - cant find The Big 3
Grand Prixs Of North America • View topic - Alternator REwire
Grand Prixs Of North America • View topic - Alt re-wire upgrade
Grand Prixs Of North America • View topic - Where is the engine ground to chassis wire? upgrade
Page 2 of this last link has a good diagram and information.

I'm really not bashing you to start off I just want to make that clear. I'm going to side with Matt though because like usual he is right. without you having a fuse in between the alt and the fuse you are just asking for trouble because that wire isn't going to give out if your alt fails and it starts pumping more power then it is capable of producing. that will cause a fire. So what I think you should do is take what he says as constructive criticism and just add it to your thread because it is very good and complete other then that "little" problem. Like I said I'm not bashing you or your thread because you did a great job, great pics and explanations etc. but Matt is right and I know you need to fix that issue. great job man and keep up the work

Would he want to put a fuse in between the fuse box and the battery in his setup for a little extra protection?

he really isnt though he is just blunt. Im pretty sure that the original is fused but I am not going to argue with you because I know that Im right that the next wire needs to be fused and at 10$ for a fuse why not play it safe?

It's not an actual fuse, it's a "fusable link" It's going to look like the wire cause it's wrapped in shrink wrap. What a real big three should look like... fused off the alternator.

<---not a fan of Big 3 gimmick. I apologize if this comes off as thread bashing but majority of the public has no need for it

I only see relevance for those who utilize an H.O. alternator. But at that point I still don't see why anybody needs an H.O. unless they're big into SPL bass competitions. However, those kids do better with batteries than an H.O. Design and efficiency of the speaker+box plays a big role too. Some guys can be real slick with just 1kw.

Maybe we need to make a list of what/who benefits from Big 3?

But really when you look at it, gm kinda messed up the idea that using 10 gauge for the alternator wire and ran it all around the engine compartment, no way that 7 feet of 10 gauge will carry 100 amps as efficently as 4 gauge will.

Originally Posted by sic6

Thanks for the write up man.

Not a problem.

Originally Posted by casper129

Figured I would make an appearance on here... How you doin 1800Collect.

I benefit from the Big 3...

And no, I don't have a HO Alt.. Yet.

But Vdroop IS an issue for you I can't say most of these kids really need to delve into it that deep. Do you know anything about Aperiodic enclosures? PM if ya do!!!

EDIT: I think the under-lying issue is defining the benefits of Big 3. A lot of the people getting into car audio are becoming very trendy with this mod. We need a thread that is void of all this banter and really lays out the pros/cons of implementing "Big 3" upgrades. I'd be a poor candidate because I see much better solutions so long as we're not talking about SPL competitions. I'm running A/B power supply amps and I only have problems with "dimmed lights" when the vehicle is off. The amps are "stated" for 800@2ohms for subs, 50x2 for full range passeves @4ohm, and ~320x2 @4 for some passives running up front. That's a lot of power to kick around on 4awg. I've seen my DIC get up to 15.2V and my read out in the back ~14.7 during the cold mornings. This is all ran on 4awg and I have no issues with daily driving and music. I can turn everything full blast, seat heaters and all, but I don't have issues with stock configurations....maybe I'm just lucky?

Maybe people place more emphasis on "power" than needed?<----that's what I believe. I don't need my windows to race up and down to make me feel better :/

Originally Posted by Mikey

I think the your write up on the subject is fine. The other people with points of interest may be indifferent though.

However, they should all be respectful and take those different points to enhance the write up so we all can do it right.

Most of all, Isn't this forum here to help each other preserve & max the efficiency of our cars?

I got the big three & my sound system is awesome, my hid's both headlights & fogs, and all electrical functions work great with out going to a H.O. alternator.

Take what you can use and be cool folks.

I have all the things you've mentioned and no big three yet my electrical system is doing just fine, in fact, I monitor it via a voltmeter gauge I have installed in my car.

Originally Posted by chickenfried

my opinon: great write up, very well put together and very informative! looks liek you spent alot of time to get it right. i did the 3 on my last car, did not fuse the pos. wires and never had any problems. i will be looking into this thread when i deside to 3up the gtp! thanks man!

Just because you havn't had a short doesnt mean you don't have a flaw in your electrical system.

Go look at your fuse box in your house, theres a main breaker for the entire panel. The same thing applies in your car. You have one massive fuse called a fusible link. Google it, you'll find many articles on it. Its not necessary, but neither is any fuse for that matter but its recommended for safety reasons.

Just because it works without it doesnt mean you shouldn't have it.