Hello all i have a 2004 i6 swb trailblazer ls. I also bought a lwb 2004 5.3 trailblazer lt that i planned to replace transmission but the frame is too far gone with rust. Now im rolling the idea around of swapping said v8 for the i6. I would like for people that have done the swap to share their experince to see if its something i would be willing to do. Thank you.
Swap
- Thread starter Trailblazen04
- Start date
Mike534x
Member
- Apr 9, 2012
- 926
From the swaps I've seen (many not completed), its a challenging task. One being that engine mounts would need to be fabricated. Another is tearing out the wiring harness from one truck and putting it into the next as well as the PCM/BCM change. I don't remember but I think the fuse box would need to be changed out as well, and the bell housing on the tranny would need to be swapped.
I know I'm missing a ton more, but that's all I remember off the top of my head.
I know I'm missing a ton more, but that's all I remember off the top of my head.
HARDTRAILZ
Moderator
- Nov 18, 2011
- 49,665
Most LWB are 4.2 actually. The frame is different though in other ways.
Mooseman
Moderator
The engine mount brackets are bolted to the frame and can be swapped out. The rear diff will also need to be replaced with the 8.6 from the EXT/V8's as the SWB 8.0 won't survive long behind the V8. Check the gearing in both.
Having the full donor truck is just about the best scenario for doing this. There are some unknowns such as how the I6's BCM will work with the V8's PCM and if the underhood V8 harness and fuse box will marry up with the I6 body wiring. The BCM may need to be reprogrammed to a SWB V8 version. I wouldn't just swap in the EXT's BCM as it has stuff that the SWB doesn't have, like the rear HVAC or other options not in the SWB.
Physically, it's very doable. It's the electronics and wiring that are the big mysteries.
Having the full donor truck is just about the best scenario for doing this. There are some unknowns such as how the I6's BCM will work with the V8's PCM and if the underhood V8 harness and fuse box will marry up with the I6 body wiring. The BCM may need to be reprogrammed to a SWB V8 version. I wouldn't just swap in the EXT's BCM as it has stuff that the SWB doesn't have, like the rear HVAC or other options not in the SWB.
Physically, it's very doable. It's the electronics and wiring that are the big mysteries.
Blckshdw
Moderator
I did this once, with a former member's SWB Voy, it was also an I6 though, but nothing went sideways and we were able to drive it with no issues. Just had to complete the security relearn.
I am in the process of doing this exact thing. One of the issues is that the engine sits forward further than the straight 6 and the transmission cross member sits to far back. I am getting rid of the 4x4 all together. The only issue that I see that I will have is the wiring that everyone has mentioned. I am thinking about just doing a stand along management system instead of trying to use the wiring harness. Also you will need to swap all of the AC, fuel, and brake lines over from the donor car as they are different as well.
So im thinkning i would swap over all the harnesses from the lwb including the bcm and body harness and have my swb just think its a lwb.. yea i planned on using the diff from the lwb even if i dont do the engine swap as it has the g80 my swb is 2wd so i dont think the gearing matters. Swb has the gu6 lwb has gt4.
HARDTRAILZ
Moderator
- Nov 18, 2011
- 49,665
Mooseman
Moderator
Definitely better with the GT4 either way.
I think the swap you're proposing is doable. The only thing for the BCM, I think, is the HVAC. If both are the same (auto vs manual), you should be good.
I think there have been a few but either they don't complete them or don't tell us about it.
I think the swap you're proposing is doable. The only thing for the BCM, I think, is the HVAC. If both are the same (auto vs manual), you should be good.
I think there have been a few but either they don't complete them or don't tell us about it.
My swb is a ls it has the manual hvac, the lwb is a lt and has the fancy automatic one. Maybe if i get the bcm flashed for a lwb ls with the v8 it would work?
Mooseman
Moderator
The BCM itself phycally is no different. It's the programming. It goes by VIN so you'd need to find a same year and option spec'd VIN for your SWB with a V8. We do have a VIN's with RPO's list