2005 malibu 3500 to 3900 swap

[mattfoo83]

How straight forward is this? I was told by a gm tech, just swap ecm and engine and call it a day. Any truth to this?

[bszopi]

I'd have to say no. You would also need the wiring harness, as a minimum. And then the 3900 PCM probably won't be set up for the same transmission as you currently have. So then you'd have to look into reprogramming with possible repinning of the harness to match your tranny (not sure its even possible), or do a tranny swap. And then there would be a lot involved with that as well.

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[Superdave]

the 05 Malibu has the gen3 3500, the 3900 is a gen4 engine.

you will have motor mounting issues but that's the easy part. I agree with Bszopi that for this to work you should swap in the entire engine, trans, harness and ECM.


There is plenty of power to be had with the engine you already have, i've got the same one in my Camaro and it's been pushing out over 300 @ the crank since 2007. Check out WOT-Tech for some good cam choices and maybe a set of headers.

[mickaz]

the weakest part of this Malibu is the tuning...the computer is tuned for economy. I'm pretty sure a Malibu is a fast(er) machine then we think

[Joseph Upson]

The easiest way to do this without swapping computers is to convert the 3900 to fixed cam operation so that it comes out like a 3500 with increased displacement. Some versions of the engine already use the same intake manifold cover as the Gen 3 3500. I believe although I'm not exactly sure, you would have to use the 06 model 3900 because there apparently was a crank trigger wheel change later. If you're going to build the engine simply use the crank from your 3500. I've had both engines and don't recall them being all that different externally in the places that count except for the EGR abscence and coolant return up front on the 3900 that you can work around.

I'd really exploit the 3500 first, it would be much less of a hassle since you're trying to run the OE PCM as suggested already.

[mattfoo83]

Ok. This is my daily, I have a friend that totaled his 3900 powered uplander and I have a chance to get it and from what he said its a simple long block swap. I guess it isn't. Thanks for the info guys.

[mattfoo83]

What about just swaping shortblocks and putting a fixed 3500 cam into the 3900 block? I have the 3900 sittting at my house

[Joseph Upson]

You'd be better off buying power adders for your 3500 than going through that trouble for what you stand to gain from that swap.

[mattfoo83]

ok one more thing.. and this is without searching so please dont flame but if i go with the super nice TB that wot tech sells. how do i convert it to able driven. the pedal and cable swap isnt a big deal, im worried about the electronics getting unplugged.

[Joseph Upson]

ok one more thing.. and this is without searching so please dont flame but if i go with the super nice TB that wot tech sells. how do i convert it to able driven. the pedal and cable swap isnt a big deal, im worried about the electronics getting unplugged.

You can't do that without addressing the PCM programming. If anything you have to address the torque management section of the programming so that the PCM applies 100% of your throttle input without editing if that's possible in the programming. Electric throttles I do believe are anti abuse components along with a little emissions management benefit. My experience with them would have me convert to cable operation also.

[mattfoo83]

thats what i was getting at. so just leave the electronics unplugged and convert to cable? i know cruise wont work i just dont want the trans to not shift or shift funny and other hazards to appear from disconnecting the drive by wire setup

[Joseph Upson]

thats what i was getting at. so just leave the electronics unplugged and convert to cable? i know cruise wont work i just dont want the trans to not shift or shift funny and other hazards to appear from disconnecting the drive by wire setup

I believe you are missing the level of complication involved. Even with the throttle unplugged you still have input to the PCM from the accelerator pedal, when the PCM detects that input does not match output at these two parts it will set a code. Practically everything is tied into the PCM or BCM and it is very likely that the transmission will not function properly if you attempt to bypass either of those parts by simply unplugging them. The TPS sensor is built into the throttle body and that causes a problem all its own if unplugged. I gather by some of the things you are considering that you are not very familiar with how many of these parameters interact with one another and the consequences when one fails or is disconnected, for example, without TPS input the PCM can not detect throttle blade position or rate of movement, so fueling may lag behind throttle input. Regardless of whether the engine runs you can be guaranteed it will not be well if you try to defeat sensors by simply unplugging them.

[mattfoo83]

I believe you are missing the level of complication involved. Even with the throttle unplugged you still have input to the PCM from the accelerator pedal, when the PCM detects that input does not match output at these two parts it will set a code. Practically everything is tied into the PCM or BCM and it is very likely that the transmission will not function properly if you attempt to bypass either of those parts by simply unplugging them. The TPS sensor is built into the throttle body and that causes a problem all its own if unplugged. I gather by some of the things you are considering that you are not very familiar with how many of these parameters interact with one another and the consequences when one fails or is disconnected, for example, without TPS input the PCM can not detect throttle blade position or rate of movement, so fueling may lag behind throttle input. Regardless of whether the engine runs you can be guaranteed it will not be well if you try to defeat sensors by simply unplugging them.

no I am understand completely. i didnt know if it was a way around it. i was pretty sure there wasnt, but it doesnt hurt to ask.

[Shane]

Anyone know what cars came with the non-vvt 3900? I want it for my beretta, I can get one from an 06 g6 for $550.

[Jonpro03]

I don't think there is a non-vvt 3900.