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Discussion Starter #1
Hi everyone, i just picked up an 07 GMC 3500hd with the 8.1 and Alison 6spd. I have a question about swapping the trailer brake and GM harness from under the dash, will the setup from my 03 Chev 1500 swap right into the 07 3500hd (plug and Play) style?

Thanks
Bill
 

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Assuming since you said it is an 8.1 it is a 2007 Classic, so yes it will plug and play directly. 03-07classic are the same.

99-02 and 03-07classic use the same plug, but the pin outs changed, I learned this the hard way when I swapped my controller from my 01 to my 03, when I turned the headlights on the truck it locked up the brakes on the trailer :eek: Luckily I noticed this before leaving the house, swapped a couple pins and it was good to go.

I don't know about the 07.5+ NNBS trucks though.
 

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new body style does not have a plug, blunt cut wires under the dash need to be hardwired to the brake controller, as well as two leads hooked up under the hood, (one next to steering column and one next to fuse box, sometimes you need to install the fuses as well). the blunt cut wires under the dash should have a tag telling you which wire color is which on the truck end
 

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Discussion Starter #4
Thanks for the info, yes it is an 07 classic. I've read about two different places to install the 40 amp fuse in the fuse box under hood to get 12v power to the trailer batterys, one says to put it in stud #1 location. The owners manual I downloaded reads like this. I'm not sure which one to use, from how it reads stud 2 is the right option.

STUD #1
Auxiliary Power (Single
Battery and Diesels Only)/
Dual Battery (TP2) Do not
install fuse

STUD #2* Accessory Power/Trailer
Wiring Brake Feed

Thanks
Bill
 

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Thanks for the info, yes it is an 07 classic. I've read about two different places to install the 40 amp fuse in the fuse box under hood to get 12v power to the trailer batterys, one says to put it in stud #1 location. The owners manual I downloaded reads like this. I'm not sure which one to use, from how it reads stud 2 is the right option.

STUD #1
Auxiliary Power (Single
Battery and Diesels Only)/
Dual Battery (TP2) Do not
install fuse

STUD #2* Accessory Power/Trailer
Wiring Brake Feed

Thanks
Bill
Should be Stud#2 assuming your 8.1 has the TP2 RPO code.
 

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Discussion Starter #6
I looked up the VIN on Comp Nine and no I dont have the TP2 option. looks like I have to use stud #1

Thanks for all the help
Bill
 

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I looked up the VIN on Comp Nine and no I dont have the TP2 option. looks like I have to use stud #1

Thanks for all the help
Bill
You could have much easier opened your glove compartment and looked for the RPO code on the sticker or just popped your hood and seen if you have two batteries or one.
 
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