Need Help with my 4.3 to 5.3 engine swap...

[smith02e]

Hi there!

Been looking on these forums for awhile, but could not really find the answers I needed. I have a 2003 Chevy Silverado 4x4, regular cab short bed, with a 4.3L engine paired to a 4L60e. I have huge plans for this truck, and part of it is getting that old 4.3 outta there and getting my 5.3 dropped in. The 5.3 I picked up was out of a 2003 Silverado of the same year. 200k miles on it, but a strong runner when pulled, have not checked casting #, but I believe it is an LM7. Before I bought the motor I did prior research and found on some forums that it was very important to get the same year of engine especially for the 2003 model year, because the 99-02 5.3s were outdated and had some computer differences between the PCM/ECM's. I should mention that the 5.3 that I bought came with the whole wiring harness and looks to be DBW. Obviously, the 4.3 is DBC and one of the two need to be converted. I am asking for guidance on what to do overall conversion-wise (general pointers & such), and also what to do about the whole throttle situation. I should also mention that the wiring harness on the 5.3 did not come with a DBW throttle pedal. Would it be easier to convert my system on my truck to DBC and deal with the potential computer and compatibilty issues? Or easier to convert my wiring harness on my motor to a DBC setup?

Please help!!

[5FDP]

If it came with the complete harness I just drop that in and buy a new throttle pedal.

Not all computers allow for drive by cable swaps, it would have to have the correct IAC drivers on it and then you'd be adding in some wires to make that work.

You'll have to write entire a 5.3 calibration into your computer if the harness didn't come with a PCM.

[AnimateMe]

Did your complete harness come with the TAC and harness that goes from the TAC to the pedal? If not, you'll need them too.

[smith02e]

If it came with the complete harness I just drop that in and buy a new throttle pedal.

Not all computers allow for drive by cable swaps, it would have to have the correct IAC drivers on it and then you'd be adding in some wires to make that work.

You'll have to write entire a 5.3 calibration into your computer if the harness didn't come with a PCM.

Understood. Thank you! How hard is the swap? Can you provide some links to some forum guides and maybe some other helpful pointers? That would be much appreciated!! I will keep this thread open until I get that motor swapped in, in case I have any further troubles or questions...

[Little_Lee]

wouldnt the stock p59 that came in that truck have the IAC drivers in it? considering it is a 4.3l with DBC already..

I am doing the same swap and am trying to come up with a way to keep my original pedal. seems like on HP tuners you can set the ETC axis to 0 and that allows the iac to work.. correct me if i am wrong, as long as you have the correct harness and programming in the stock computer maintaining DBC is possible right?

biggest issue I am facing is finding matching OS #'s for segment swaps to make the 4.3 to 5.3 tune a bit simpler. let me know if i have got this right.

Bad Bitch 5.3l 1st Try.hpt