OR VietVet Is Still Throwing $$$ at 2005 Z71

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GMT800 2005 Tahoe Z71
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I would put a quick disconnect on the positive wire connecting the 2 batteries. I get having the 2 batteries always connected will ensure that the second battery remains fully charged without any action on your part. But, having them both always connected won't alleviate that situation of the boy playing your truck's radio without the truck running and running both batteries down together, or inadvertently leaving some device on in the truck overnight and having it run both batteries down together.
Good call. Will do.
 
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If I'm not mistaken--isn't there a battery tray already there from the factory? Pretty sure there's one there. Take a look on the passenger side--under the fender brace.
This is what is there now. Does not look like a battery tray to me.

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If I get the Dorman tray at RA and with shipping and 5% off, is around $36.00. If I use my military discount at O'Reilly's, I can get it for $35.95

I did look and the 4 attaching bolts at the firewall are the same and the 1 attaching bolt at the other end would go under the ear of the coolant reservoir bottle. Then use a standard battery hold down and bolt.
 

Joseph Garcia

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This is the quick disconnect electrical connector that I use. Don't be concerned about only 175 Amp rating, because it is a continuous rating, and these connector can easily handle 500 Amps on a few seconds basis to start the truck, when needed.

Quick Disconnect.jpg
 
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This is the quick disconnect electrical connector that I use. Don't be concerned about only 175 Amp rating, because it is a continuous rating, and these connector can easily handle 500 Amps on a few seconds basis to start the truck, when needed.

View attachment 488168
Yes, I have used one of these before. I had an off road rig and had a female trailer hitch at both ends and could use my winch at either end and just plugged in the cable connection with this same set up.
 
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So, today I removed the upper brace and the lower pan. I installed this battery pan and got the right battery hold down bolt for the extra hold down I had in my tool box. The best sizing, for the bolt, is a 2" long x M8 x 1.25. I did measure the height at the front, close to the coolant reservoir bottle, at the height to where the brace would bolt back in....6" at the most. The typical side terminal 12 volt battery would be 7.5" to 7.8" and clears fine at the back and will clear at the front but without the brace. Then just install the cables and a positive cable quick disconnect.

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When I converted my 03 Yukon to dual batteries, maybe in 2014, I purchased the Factory Police Dual Battery positive wire set up. I wish I had done this another way. I had to wire it to the starter and route it from there. What a pain. At that time I did not know to go in through the tire well so I did it from below and wasted a few hours swapping the cables at the battery. I hope you have a better plan than I did. Looks lke you are almost there.
 
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When I converted my 03 Yukon to dual batteries, maybe in 2014, I purchased the Factory Police Dual Battery positive wire set up. I wish I had done this another way. I had to wire it to the starter and route it from there. What a pain. At that time I did not know to go in through the tire well so I did it from below and wasted a few hours swapping the cables at the battery. I hope you have a better plan than I did. Looks lke you are almost there.
I have done this before, I think I explained earlier, when I was four wheeling and had two batteries. I did not have the quick connect between the batteries on the positive cable. With a disconnect at the positive cable, between the two batteries, I can recharge the second battery when I want to. Theoretically, I can use 2 quick disconnects and start off of either battery. I don't run any special electrical loads on my system. No big screen in my dash and no special stereo system or video system. Stock factory radio and CD player.

I felt at the mercy of the 800 number call for help tow companies. Minimum tow home, 44 miles away, was $550. That is a freakin' rip off. The local tire shop brought me the new Interstate battery and charged me a $30 service call, 5 miles away, and with the 3% c/c fee, my total was $262.60.
 

Joseph Garcia

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I have done this before, I think I explained earlier, when I was four wheeling and had two batteries. I did not have the quick connect between the batteries on the positive cable. With a disconnect at the positive cable, between the two batteries, I can recharge the second battery when I want to. Theoretically, I can use 2 quick disconnects and start off of either battery. I don't run any special electrical loads on my system. No big screen in my dash and no special stereo system or video system. Stock factory radio and CD player.

I felt at the mercy of the 800 number call for help tow companies. Minimum tow home, 44 miles away, was $550. That is a freakin' rip off. The local tire shop brought me the new Interstate battery and charged me a $30 service call, 5 miles away, and with the 3% c/c fee, my total was $262.60.
You absolutely won't regret it.

I ran the 2 battery cables for the second battery along the top of the firewall, and I have the quick disconnect on the side of the second battery, about where the hood spring hinge is. Easy to get to.

I connected the negative cable to the engine block, right where the primary battery negative cable is connected. I connected the positive cable to the main fuse block on the firewall (before the fuse) where the primary battery cable is connected. I put a cable protector sleeve on the cables to the second battery, going across the firewall, and zip tied it in place.
 
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You absolutely won't regret it.

I ran the 2 battery cables for the second battery along the top of the firewall, and I have the quick disconnect on the side of the second battery, about where the hood spring hinge is. Easy to get to.

I connected the negative cable to the engine block, right where the primary battery negative cable is connected. I connected the positive cable to the main fuse block on the firewall (before the fuse) where the primary battery cable is connected. I put a cable protector sleeve on the cables to the second battery, going across the firewall, and zip tied it in place.
Pics?
 
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The truck is at the shop right now, getting the transmission's hard downshift fixed. I'll send pics, when I get the truck back.

I do have this pic that only shows the protected cables going across the firewall.

View attachment 488282
Yea, pics from one side to the other and at the p/s tray area, would help and of course the d/s battery area. Thanks.
 
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Ok, so I did slip a new 78 series battery, in to the second battery tray yesterday and it was a little tight to snake in there but when I held my tongue just right, it slipped right it. The hold down fit perfectly. It felt very solid as well. Now I just need those pics from @Joseph Garcia and I can continue with the cables and disconnect(s). If @Joseph Garcia has part numbers, that would be even better. Thanks again.
 
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So, recently I had my battery go dead with no warning at all. It was exactly 5 years old Interstate 78 series AGM battery and I replaced, via a service call from a guy named Kanyon and big enough to earn it, it is an Interstate 5 year non AGM battery. The alternator that is on the Tahoe is also 5 years old and was a new GM 15128978. Cannot get a new GM battery at RA any more. I did some research and a guy at Automotive Parts Specialists wholesale warehouse in town, named James, did me a solid and researched and found a new GM alternator number 19338659, 160 amp and does show in the application guide at Summit but strangely enough not at RA. I can get it at RA but it was not in the NEW application at RA. I had a $116 credit and paid $85 difference, including shipping. Installed today and is solidly working great. The old one was still working but had very slight front bearing noise and could hear it with my mechanic's stethoscope and also, faintly on the bench. I am preparing to install a new second battery and will wire in with disconnects, as per a recommendation by @Joseph Garcia, and wanted a new alternator for the whole process and with the pending credit, I pulled the trigger. Will sell the old one here locally. here is some pics of the install and I did a throttle body cleaning while in there.

I am sure most know of this but in the 6th pic you can see the little ears the attaching bolts slide thru to mount the alternator. When remove the bolts, grab the top back of alternator and pull hard to tilt forward and that will put pressure on those ears to move forward and help create space to lift the old alternator out of the cradle. When alternator is out, then take a small tick hammer or dead blow hammer and tap the ears forward from the back side. That will create new alternator install space and when you install and tighten the bolts back in, the bolt pressure will move the ears toward the alternator and tighten down the clearance space.

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The alt pulleys look a bit different, but maybe that's just the larger edge lip on the new one or the way it was machined. You didn't happen to measure the pulley diameters to compare, did you? Just curious about it.
 

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