03 silverado 4.3 to 5.3

Hey guys ive been searching my ass off on here and need some help.I bought a 03 silverado with 4.3 5 speed with 76,000 miles im wanting to throw in a 5.3 i know i need a 4.8 clutch and fly wheel but what year 5.3 and harness bc i dont have drive by wire i have a throttle cable and i found a good deal on a complete 01 5.3 with harness and any part i need but i dont wanna buy it if it wont work,im tryin to get all my stuff together before i start so im not searching for stuff i appreciate ur help and any tips would be great

So easy a caveman could do it. You need a engine harness from a 99-02 truck that has a cable throttle body, it don't matter if its a automatic truck. The speed sensor connector for the transmission is what you really need. Un bolt the 6cyl harness from the fuse box, connect the v8 harness, custom tune for the pcm. There is a few other steps but its actually pretty simple.

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Originally Posted by jsisk

Hey guys ive been searching my ass off on here and need some help.I bought a 03 silverado with 4.3 5 speed with 76,000 miles im wanting to throw in a 5.3 i know i need a 4.8 clutch and fly wheel but what year 5.3 and harness bc i dont have drive by wire i have a throttle cable and i found a good deal on a complete 01 5.3 with harness and any part i need but i dont wanna buy it if it wont work,im tryin to get all my stuff together before i start so im not searching for stuff i appreciate ur help and any tips would be great

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keep the 4.3 harness to splice in if u want reverse lights. An LS flywheel-disc-pp, V8 engine mounts and frame mounts, both a/c lines and compressor if you dont have one, keep the fuel lines on the truck. ask questions, im sure im forgetting some things

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Originally Posted by blacstar

keep the 4.3 harness to splice in if u want reverse lights. An LS flywheel-disc-pp, V8 engine mounts and frame mounts, both a/c lines and compressor if you dont have one, keep the fuel lines on the truck. ask questions, im sure im forgetting some things

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do i need ac lines from the 5.3 and if so which ones the ones that run acroos the engine or the ones that go in the box the 2 aluminium ones and thanks guys for ur help

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Originally Posted by TXSZ66AVLANCHE

So easy a caveman could do it. You need a engine harness from a 99-02 truck that has a cable throttle body, it don't matter if its a automatic truck. The speed sensor connector for the transmission is what you really need. Un bolt the 6cyl harness from the fuse box, connect the v8 harness, custom tune for the pcm. There is a few other steps but its actually pretty simple.

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Uhm. No. You're wrong.

You need to convert to DBW. It's a not a big deal at all, the truck is already setup for it and the pedal and TAC module will bolt right in. You need an 03-05 harness and pcm. You need the entire A/C setup, compressor, compressor bracket and any lines that attach to the compressor

You don't need to convert to drive by wire, you can....but only if that's what you want to do. Since the v6 truck is already a cable throttle its just one less step.

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Originally Posted by Frenchy

Uhm. No. You're wrong.

You need to convert to DBW. It's a not a big deal at all, the truck is already setup for it and the pedal and TAC module will bolt right in. You need an 03-05 harness and pcm. You need the entire A/C setup, compressor, compressor bracket and any lines that attach to the compressor

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why would i want to convert to dbw if my truck doesnt have it and the truck im getting the 5.3 from doesnt have it?

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Originally Posted by jsisk

why would i want to convert to dbw if my truck doesnt have it and the truck im getting the 5.3 from doesnt have it?

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the harness/fuse box pins are different, its alot easier to just do what Frenchy said! save u time and stress

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Originally Posted by TXSZ66AVLANCHE

You don't need to convert to drive by wire, you can....but only if that's what you want to do. Since the v6 truck is already a cable throttle its just one less step.

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Yes. You do. I have done the swap. Have you? The 99-02 engine harness and PCM will NOT work with the 03+ BCM. Without serious, re-engineering.

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Originally Posted by jsisk

why would i want to convert to dbw if my truck doesnt have it and the truck im getting the 5.3 from doesnt have it?

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You want your truck to run without countless headaches right? My truck is a swap. There's other guys who have tried keeping DBC in the newer trucks, guess what? Those trucks are now DBW. There was a ton of changes between 02 and 03 electrically. Go DBW. or don't listen, do it ass backwards, go about it, have lots of trouble and go DBW anyway.

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Originally Posted by Frenchy

Yes. You do. I have done the swap. Have you? The 99-02 engine harness and PCM will NOT work with the 03+ BCM. Without serious, re-engineering.



You want your truck to run without countless headaches right? My truck is a swap. There's other guys who have tried keeping DBC in the newer trucks, guess what? Those trucks are now DBW. There was a ton of changes between 02 and 03 electrically. Go DBW. or don't listen, do it ass backwards, go about it, have lots of trouble and go DBW anyway.

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Im not understanding at all so if my truck is not dbw and the engine im gettin is not dbw i still need to convert it?If so could i just by a 03 5.3 and the harness work with out doing dbw?

Is there a thread how to convert dbw bc ive searched and cant find anything?

Since im being told i need to convert to dbw should i just go ahead and get a 6.0 instead bc i found one out of a 03 but thought it would be a pain to do dbw so i didnt get it

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Originally Posted by jsisk

Since im being told i need to convert to dbw should i just go ahead and get a 6.0 instead bc i found one out of a 03 but thought it would be a pain to do dbw so i didnt get it

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it doesnt matter which engine you pick, just get a 03-07 harness, tac module, harness between gas pedal and tac module and the pedal its self. if this is too complicated for you, dont do it! sell urs and go buy a v8 truck

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Originally Posted by blacstar

it doesnt matter which engine you pick, just get a 03-07 harness, tac module, harness between gas pedal and tac module and the pedal its self. if this is too complicated for you, dont do it! sell urs and go buy a v8 truck

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its not to complicated just gettin 10 diff answers is whats confusing just want to get the right shit before i start on it

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Originally Posted by jsisk

its not to complicated just gettin 10 diff answers is whats confusing just want to get the right shit before i start on it

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calm down lil man, u kept askin same question. and it was only 2 diff answers. I have done the swap the the truck u see in my 'sig'. I almost too easy. just get the pedal,module, and harness. its all plug and play

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Originally Posted by blacstar

calm down lil man, u kept askin same question. and it was only 2 diff answers. I have done the swap the the truck u see in my 'sig'. I almost too easy. just get the pedal,module, and harness. its all plug and play

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No biggie man the module?Where will it be mounted at in the doner truck?and the pedal just mounts like the cable one ive searched but the search feature on here isnt that great.Thanks for the help i just want to make sure i got everything bc im gona do it on my 3 day weekend and who should i get a tune from for the vats and stuff like that

its a lil bit bigger than a index card, to the drivers side of the booster against the firewall, 2 connectors coming off of it; one goes into the cab to the pedal and the other to the engine harness. yes the pedal mounts the same. send nelson performance ur pcm, very good guys/gals.

Seriously budget a month in a rental car while doing the conversion

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Originally Posted by RedHeartbeat

Seriously budget a month in a rental car while doing the conversion

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This. Just when you think you have everything you need, you don't.

In my option DBW is the way to go. On my 06 I converted from 4.3 cable to 6.2L DBW and also converted from class II to CAN. If you decide to go DBW give us a call and we wE can assist you

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Originally Posted by Ray@NP

In my option DBW is the way to go. On my 06 I converted from 4.3 cable to 6.2L DBW and also converted from class II to CAN. If you decide to go DBW give us a call and we wE can assist you

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thanks for everybodys help and one more thing my truck is a wt does that matter at all?Ill just up date this thread when i start doing the swap

My truck is a W/T, most my parts came from a fully loaded Z71

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Originally Posted by Frenchy

My truck is a W/T, most my parts came from a fully loaded Z71

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I'll trade you, I want a black truck instead! and i will throw in a full tank of 87 octane! just to sweeten' the deal

Thanks fenchy i was hopin i was gona need a diff harness or some crap bc mines a work truck

Hey guys need ur help om one more thing,which 6.0 to get?I found a 05 complete with 70,000 miles for 900 bucks with harness.Thanks

Sounds like a good deal to me

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Originally Posted by RedHeartbeat

Sounds like a good deal to me

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will that year be ok in my 03 as long as i get the harness?And should i be alright with my fuel lines if i cut and use the fittings that are in the sticky on here

You can use any 01+ engine. The only difference in the actual engine between pre-03 and post-03 is the throttle body. And returnless or return fuel rails. Easy to swap either around.

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Originally Posted by Frenchy

You can use any 01+ engine. The only difference in the actual engine between pre-03 and post-03 is the throttle body. And returnless or return fuel rails. Easy to swap either around.

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Thanks Frenchy,how do i know if i have a return fuel set up?I have to lines that run into my spider injection but i seen on here it might be returnless.

Your trucks an 03? It's a return setup

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Originally Posted by Frenchy

Your trucks an 03? It's a return setup

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Thanks again lol ill stop being a pest now and get to work got my engine mounts in from dealer and new clutch kit and fly wheels