New 2020 GMC Sierra needs high output alternator help!!

Toomnymods

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Hello,
I’m planning a large sundown audio build and have everything I need cept for the alternator.
Seems GMC thought it was a good idea to get rid of the belt tensioners on the 2020 6.2L L87 engine blocks!! Which this of course all but eliminates me from running a high output alternator on my truck since most alternators have a smaller diameter pulley wheel to get more rpms at idle.
Has anyone with a 2020 GMC 6.2L upgraded thier alternator? If so which alternator did you end up going with and which belt??
Please help this is the last thing holding me up from my dream build..
 

hispls

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This is a question you ought to be asking the high output alternator shops. Surely those guys have experience making this work or would tell you if it's a know problem and what to expect.

That said you could always just brute force this by using a huge battery bank. Depending what you plan to do you might be able to just get by with factory limitations on alternator.
 

Toomnymods

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This is a question you ought to be asking the high output alternator shops. Surely those guys have experience making this work or would tell you if it's a know problem and what to expect.

That said you could always just brute force this by using a huge battery bank. Depending what you plan to do you might be able to just get by with factory limitations on alternator.
already did ask them.. they are next to worthless. They all had the attitude is its not our goal to make it work.. thats on your end. We supply the alternator if if dont work for your truck thats on you..
 

hispls

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already did ask them.. they are next to worthless. They all had the attitude is its not our goal to make it work.. thats on your end. We supply the alternator if if dont work for your truck thats on you..
I suspect that's a sideways way of saying it'll likely be an issue that they have no idea of how to fix. So might go into this either with a plan to go huge on a battery bank or get an alternator and find a custom shop that can figure out how to make the belt not slip if that is an issue.
 

Toomnymods

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I suspect that's a sideways way of saying it'll likely be an issue that they have no idea of how to fix. So might go into this either with a plan to go huge on a battery bank or get an alternator and find a custom shop that can figure out how to make the belt not slip if that is an issue.
I found out that GM has a OEM 220 amp alternator option for my year truck for $174.00 Might just try this route first. My stock alternator is a 170amp.
I also have two Limitless lithium 45Ah lithium batteries I plan to put into the bed of my truck.
Maybe this will help some with voltage drop since I’ll only be using a Sundown Audio SALT-6 for the first year or so till I get the rest of my subs and the box built for the bed of my truck.
Will eventually have 3 sundown salt 6’s pushing 6 Sundown Audio 12” ZV5’s and hope I can get that elusive 160db..
 

hispls

CarAudio.com Veteran
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Sep 10, 2009
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I found out that GM has a OEM 220 amp alternator option for my year truck for $174.00 Might just try this route first. My stock alternator is a 170amp.
I also have two Limitless lithium 45Ah lithium batteries I plan to put into the bed of my truck.
Maybe this will help some with voltage drop since I’ll only be using a Sundown Audio SALT-6 for the first year or so till I get the rest of my subs and the box built for the bed of my truck.
Will eventually have 3 sundown salt 6’s pushing 6 Sundown Audio 12” ZV5’s and hope I can get that elusive 160db..
160 sealed/legal or outlaw? Not sure if you're going to get there with that cone area on anything that'll play music well sealed/legal but pickup trucks can gain huge with driver's side door/window open so that would help significantly.

Might as well go for the factory alternator upgrade for that cheap and see if that + lithium doesn't hang for you. If you really think that the belt slipping is going to be a huge issue you may just have to plan this build around overkill on batteries... may be cheaper in the long run than finding a custom shop that can re-work the entire belt and pulley system if that's a problem.
 

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