It doesn't matter where the 3400 comes from but what does matter is that you take note of what car you took it out of, and that you get the matching transmission with it. The reason I say that is because it will be easier to do that than mix and match the stuff, not to mention there's numerous variations of the 4T65E. For example, the Grand Am has 3 different variations of the 4T40E transmission, each with different gear ratios. The Cadillac Seville had its own set of 4T65E gearing and connections, that would not match up with the Monte Carlo's gearing nor with the flywheel of a 3400.

My advice is simple... get the whole thing as a set, and get a PCM tune. You have to tune the PCM for it to read the correct values of both the engine and the trans.

You will also have to do some light wiring, but nothing out of the extreme. There's variations between the 3100 and the 3400.

The real question is how inclined and dead set are you about changing the engine to something more powerful?

 

@Woodr004 - If you want to go for cheap/easy and just get her on the road, stick with a 3100. If you want improved performance by a fairly simple swap (may cost a little more and have a couple of "gotchas"), swap up to a 3400.

If you still want to upgrade to a 3400, take a look at that PDF I sent a while ago, it outlines not all, but some of the "gotchas" based on the different years of 3100 and 3400 for the swap. Heck that PDF may also help with some "gotchas" for sourcing a donor 3100.

Also, I cannot say for certain, but peaking at the shop book data, your Monte may have had a 4t60 transmission (not a 4t65). Again, looking at the shop book, it also looks like most (if not all) automatic Grand Ams from '97-'99 also had a 4t60. In 2000, the Grand Am switched to a 4t40. I don't know the issues with swapping a 4t40 or 4t65 into your Monte would be, plus as others have mentioned, just because it's the same transmission does not mean it's the same gearing and you may have to re-tune the car as a result.

 

I have another question for you all. In reading the PDF that Jason sent me, it says that 2000-2004 Chevy Impala 3400 engines are a candidate for the swap. As luck would have it, I have access to a low mileage (53k) 2005 Chevy Impala 3400. In my googling I could not see any difference between the two engines, making me wonder if this 2005 3400 will work in place of my 97 Monte Carlo's 3100. I did see that the 2005 engine used the 4t65 transmission where my 3100 uses the 4t60 I believe. Can anyone enlighten me?
Thanks!
Pat

 

I WANT THE PDF TOO!!!!!! I'm gonna start my search this summer for one to clean up and have ready when my 3100's rear main seal starts to leak much worse.

 

@Pat - Since you're email, I've tried finding out information about the '05 3400. The ONLY thing I can find is a person was told by a salvage yard that when looking for a 4T65 trans for an '05 that he MUST get the trans from an '05 (something about an extra bolt was added or alignment changed). Sadly, I don't have a way to confirm that.

@TPS221 -
Here's where you can find the PDF:
https://montecarloforum.com/forum/fw...ne-swap-46706/
Here is an additional guide from a member of MCF that did a 3100-3400 swap:
https://montecarloforum.com/forum/fw...00-swap-40684/

 

Jason, I did some more searching on the Auto Forums and saw several references to the 2005 3400 as being the same from 2000-2005, basically the upgraded 3100 VIN E. I am going to look at the engine on Sunday and will check out the bolt pattern. I might get away with just changing the wiring a bit and be able to use my current transmission or I can use a transmission from a 1997-200X Monte Carlo but if I do that I might have to change the PCM out. Either way, the engine sounds promising.
Pat

 

You can use trans pcm and wire haress from a 2000-01 lumina with 4t65. Also you can use stock pcm harness pcm and trans if in good shape

 

Good to know, when you say stock pcm harness and trans, are you referring to my current 3100 pcm setup?

Pat

 

Yup, but i highly recomend going 4t65