Lb7 to lly swap

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Dkatubi06

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Dec 30, 2015
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ok guys, this is my first post here, I would have put in on the duramax forum where I've been for a while but I just don't find the help I need. So on with my post.
I've been doing a lot of research about swapping my top end over to an lly top end. Seeing how my truck is an '02 I would need to pretty much get a custom harness from Ben. I know 2003 and up is plug and play. I searched high and low and found a 2003 lb7 in awesome running condition for dirt cheap. It is now sitting in my driveway. My question for you guys is can I take the underhood harness and swap it to my truck? Would everything still work ( gauges, trans, Ect)? I wouldn't do it until I have all my lly parts together. I'm just doing research at this point
 
clrussell

clrussell

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Sep 23, 2013
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Are you wanting to lly swap the 02 or the 03?


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Dkatubi06

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I'm wanting to swap the 02. I've read the "I've seen the impossible thread", and have searched think even messaged Russ on Facebook and got no response
 
clrussell

clrussell

pro-procrastinator
Sep 23, 2013
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To answer the question I think your asking..

No you can't take the harness off the 03 and plug it into the 02 and everything work.

Now to swap your 02 truck you need ally engine and truck side harness, ecm, etc.. You have to send the lly harness to ben to be modified to fit the 02 truck. When you get the harness back it'll be 99% plug in, and your factory 02 gauges etc will Work.

Basically if you bought the 03 truck for parts to do the swamp you wasted your money on it. If you bought it to drive while you do the lly conversion on your 02 then cool.


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RPM Motorsports

RPM Motorsports

smokinum
May 13, 2008
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Dkatubi06 said:
I'm wanting to swap the 02. I've read the "I've seen the impossible thread", and have searched think even messaged Russ on Facebook and got no response
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I only see FB messages if I'm on a desk top sorry, I haven't checked them in a while. No, you can't just use the 03 harness in the 02 without modding a few things.
 
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Dkatubi06

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Dec 30, 2015
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RPM Motorsports said:
I only see FB messages if I'm on a desk top sorry, I haven't checked them in a while. No, you can't just use the 03 harness in the 02 without modding a few things.
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Hey man I understand people are busy, I hate desktops. What would need to be modded to make this harness work.
 
rfletes79

rfletes79

Active member
Mar 5, 2010
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There are a couple ways to get this done. If you want to run it as a true LLY send your LLY harness to BT and get it re-worked for an 02 truck.

The other method is controlling the LLY with your current LB7 ECM. You'll need custom tuning to get the motor happy and run correctly. Russ is very familiar with this method and has several trucks out there running this way. You would have to stick with the LB7 turbo for this to work. I did this conversion in my 02 last year, have 20K miles on it since then and still drive it everyday. If you have any questions about my swap lmk. I followed Russ' method and purchased the tuning from him.

Rick
 
Chevy1925

Chevy1925

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Oct 21, 2009
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I literally just completed this swap on my 02.

You will need an LLY harness to send to ben. the 03 harness wont work as it has the wrong ecm connections and NSBU connections

then there is a laundry list of parts you will need to swap it all over if you want to use the LLY ECM

there is the other route that use the LB7 ECM and tuning to correct the issues but ive read guys having tuning headaches trying to get drivablilty back to like it was (if your picky). I went the LLY ECM route with Bens harness and it was 100% plug and play. well worth it imho and now i can run a VGT turbo down the road as well.
 
rfletes79

rfletes79

Active member
Mar 5, 2010
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Chevy1925 said:
I literally just completed this swap on my 02.

You will need an LLY harness to send to ben. the 03 harness wont work as it has the wrong ecm connections and NSBU connections

then there is a laundry list of parts you will need to swap it all over if you want to use the LLY ECM

there is the other route that use the LB7 ECM and tuning to correct the issues but ive read guys having tuning headaches trying to get drivablilty back to like it was (if your picky). I went the LLY ECM route with Bens harness and it was 100% plug and play. well worth it imho and now i can run a VGT turbo down the road as well.
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Exactly what this says above................... specially if you are picky, very true. The tuning would be the hardest part, if you had to start from scratch. But I'm sure someone would be willing to sell you a proven tune to keep your LB7 ECM in there and make it work. The drive ability of my 02 LLY swap is really close to what a factory LLY/LB7 would be. In the winter (right now) it does have a slight injector knock to it, but in the summer it is flawless. Its super smooth and quiet as compared to the old LB7. And has plenty of power. I was skeptical at first, but as previously stated I personally have over 20K miles on this swap. And I know Russ has Hundreds of thousands of miles out there with other swaps running this same tuning (LLY controlled by a LB7 ECM).

Either way works well, and either way will cost you some extra cash due to it being an 02. If I were doing this again with an 02 the first thing I would look at is if it is a Cali truck or Federal. If it was Federal I would do the swap the same was as I have already done. If it is a Cali truck I would purchase a harness from BT. Just my 2 cents and personal experience.
 
Chevy1925

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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Phoenix Az
rfletes79 said:
If I were doing this again with an 02 the first thing I would look at is if it is a Cali truck or Federal. If it was Federal I would do the swap the same was as I have already done. If it is a Cali truck I would purchase a harness from BT. Just my 2 cents and personal experience.
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curious why you say that? mines a federal truck and i dont really see why one way would be better than the other, unless you mean its in cali.
 
rfletes79

rfletes79

Active member
Mar 5, 2010
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Galt, Ca 95632
Federal doesn't have the EGR crap to deal with and that's the only thing on mine (as it is a cali truck) that doesn't work. I will have to address it before smog next year. Either by transferring the lb7 EGR system over or getting a harness done by BT and adding all the LLY components, including the EGR system.

If my truck was a federal truck it would be done already as is........... Federals are better and easier, imo.

I didn't send any harness's anywhere or splice any harness' at all in my swap. I used the LB7 ECM/FICM and harness from my truck and left the LLY engine harness on the LLY engine....... Plugged in the bell connectors (LB7 truck side, LLY engine side), left the VGT plug and EGR plug in the wind and haven't looked back. My oil press gage doesn't work, I run the IHI turbo and don't have EGR. But the swap was easy, as everything just plugged in. It's not perfect, but it runs great and very reliable. I work on these trucks weekly and this thing runs smoother then any LB7 or LLY that I've driven. :)
 
duratothemax

duratothemax

<--- slippery roads
Aug 28, 2006
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rfletes79 said:
It's not perfect, but it runs great and very reliable. I work on these trucks weekly and this thing runs smoother then any LB7 or LLY that I've driven. :)
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You keep mentioning that its not quite perfect, and then its perfect at the same time? :confused:

After tuning two trucks setup like this, I wouldnt touch the setup with a 10' pole. It made me want to throw my laptop at a brick wall. Granted, these were lower compression built trucks with big injectors, etc....but still, it was the stupidest thing ever. Spent days straight on it and barely got it to the "good enough" point, and Ive been tuning these trucks for 10 years.

Thats just my honest opinion, I promise im not trying to drum up business.

Ben
 
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