OBS to LSx conversion

[GM400Z]

Awesome thread! I plan on doing a 5.3 LS swap in the near future. Just put a good TBI in along with rebuilding my 4l60e :/ but I figure I can atleast go ahead and get my motor and EVERYTHING I need so when the time comes I'm ready to go and probly have them build the 4l60e up again.

I'll need
motor
cpu
wiring harness
fuel pump
motor mounts
headers/manifolds?
adapter to use my 95 4l60e

also was wondering will it will look cool but will it help the wiring process to buy a gauge cluster from a NBS 99-up?? Can't wait to find a good motor. Can't decide if I want to just find a low mileage 5.3 or re build it and build it up. Probably just go with a low mileage if I built it up I would never stop until it was insane, and that just cannot happen.

[RezinTexas]

I'm sort of confused here. Why are all you talking about buying $650 harnesses and grafting them. Why not just get a harness from the model vehicle the engine was out of, you can get one for probably $100. Am I missing something?

I was wondering this myself, anyone have an answer?

[RedHeartbeat]

No matter what harness you buy you are going to have to marry them together. Some like a simple cleaned up harness to start with. There are a lot of wires in a factory harness that you will not use and you'll be cutting a lot of terminals off a factory harness to hook into your original harness.

[RezinTexas]

No matter what harness you buy you are going to have to marry them together. Some like a simple cleaned up harness to start with. There are a lot of wires in a factory harness that you will not use and you'll be cutting a lot of terminals off a factory harness to hook into your original harness.

ok thanks for the answer.

Since I'm still new to swaps, here is an example - If I have a '97 chassis and drop in an '04 5.3, '04 tranny, '04 ecm, and '04 gas pedal - can I use an '04 harness without much splicing? what else is left on the wiring side from the ECM?

[RedHeartbeat]

There is going to be a bit of wiring work no matter how you do it. There are a few websites with detailed step by step methods for making a harness into a standalone setup. I've done a few but didn't document anything since it was just for me. I've written a ton of detailed instructions for the swaps but never for harness modification. The good thing is you can use the existing fuse block on most swaps though I've never done a 1994+ model.

[dm79]

quick question Im neck deep in doing my ls1 into 240 swap right now. But after i want to tackle a 5.3 swap into my 92 2 door yukon. as I understand it i need the 5.3 and 4l60e b/c my old 92 tranny will not work right correct? and if i swap the newer 5.3 with tranny in will i have to do any other type of conversions to make the new tranny work? new drive shafts? etc? i want to keep it 4x4. I havent found much that touches on this

[RedHeartbeat]

yeah, its best to get the later model 60e to take full advantage of what the PCM does for transmission management. I'm sure you've seen the topic 100 times that the 60e doesn't last long behind the LS engines due to all the TQ they put out, so keep the TQ management in your tune to prolong the life of the trans. A lot of guys have stripped the 4x4 front drive assembly out and gone 2wd. If you get the right engine mount adapters it will be a straight drop in replacement plus wiring, fuel system upgrade and exhaust system modifications to marry up to your old system. The Dirty Dingo mounts seem to keep the transmission in the stock location, if there are others I'm sure someone will speak up.

[ccreddell]

Yes, you can keep the stock tranny-just need to use the spacer. That being said what Red said is true-the 4l60e is happier behind the LSX. Get a good rebuild and update some internals and it will live behind the LSX just fine-as will the 700r4 with the same treatment.

[dm79]

Ya I plan on keeping the newer 4l60e just want to make sure there no hassle to keeping it 4x4 as far as driveshafts mounting up and transfer case etc. All wiring and stuff is no big deal. Just never messed with a swap with 4x4

[quickorange]

No matter what harness you buy you are going to have to marry them together. Some like a simple cleaned up harness to start with. There are a lot of wires in a factory harness that you will not use and you'll be cutting a lot of terminals off a factory harness to hook into your original harness.

I'm still confused as to what needs to be married. Is this if you're trying to keep any original electronics? I plan on only using components from my donor vehicle- engine, trans, ecu, gauges, etc.