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Discussion Starter · #1 ·
So, a few months back I was able to pick up a 2008 CTS4 dirt cheap. The original 3.6 had 200k on it and a destroyed valve train as a result of a timing chain failure. The dream of owning a CTS-V has long been in my head, but financially it’s not in the cards. when I saw this CTS4 come up for sale the ideas stated coming and I pulled the trigger on it. I figured it couldn’t be that hard to put an LS into something that already had version produced from factory.

after getting the car the tired old 3.6L was pulled out in the same weekend.
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From there the research and hunt for a donor engine began. One of the first things I realized was the AWD front cradle wasn’t going to work if I wanted to drop the LS right in to the factory mounting spots of a V. I was able to get my hands on a RWD/V cradle Out of a local junk yard( I took some measurements and everything is going to bolt Up perfectly). About the same time I found the perfect donor vehicle for the LS. A 2001 Silverado 2500 RWD 6.0L LQ4 paired to a 4L80 that was running and driving with only 85k on it.
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This was more than ideal because I could see it run and have plenty of extra parts to sell off to help fund the build. The 6.0 is going to get alittle love before being transplanted into my CTS. The plan for it now is a mild build with 0.040 cosmetics head gaskets, lifters, PAC trunion and spring kit, a sloppy stage 2 cam, and some other odds and ends.

Things start to slow down a bit now. I was having trouble figuring out some ways to go about things on this build that is until I found these lovey forums. Did some digging and came across the legend of a man who did this swap already @Big_kid. I looked through his swap forum and it was a huge help for a lot of the Process even tho there’s some differences between our swaps. Right now I’m at a bit of a stand still on parts due to me being stationed in Alaska, so parts tend to take awhile to get here…..

While I’m waiting on parts I want to get some other details of swap figured out. Wiring is a huge question for me and I want to take
the best route possible. Another question is the fuel system. Am I able to run the stock pump that’s on it now? I would assume the 6.0L is gonna be a bit more thirsty then the stock 3.6L. Front accessories are another big one, what alternator, water pump, etc should I run? Looking forward to hearing from you guys and keeping you updated on the progress!!
 

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08 CTS L76/MYC conversion
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Nice to see someone else doing this swap (I know there are others but are not documented).

depending on what you want to use the car for will determine your wiring, do you want to keep A/C, do you want to keep ABS, do you want to keep emission, ETC

The stock V6 fuel pump should be fine, I’m about 400ish HP and still on the stock V6 fuel pump

there is limited space up front with the two extra cylinders your best option is corvette/CTS/G8 accessory spacing.

some problems you will run into with your donor engine/trans choice.
2001 was GEN III 24x low speed communication drive by cable
your CTS is GEN IV 58x high speed communication drive by wire
all the computers communicate together and you will have two different generation computers trying to talk and will likely get an error because of this. Your swap can still be done but you will need to look at the engine/trans as a “separate” or “stand alone” system. you will need to “hard wire” a few things like start command, engine temp gauge, RPM gauge, A/C controls (if you want A/C). again, depending what you want to keep or willing to give up. For me I wanted to keep everything, that’s why I stayed with the same generation computer system, everything works like the factory…

CTS-V2 engine mounts should bolt directly to the LQ4
you will need a custom made trans mount for the 4L80
 

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One of the first things I realized was the AWD front cradle wasn’t going to work if I wanted to drop the LS right in to the factory mounting spots of a V. I was able to get my hands on a RWD/V cradle Out of a local junk yard( I took some measurements and everything is going to bolt Up perfectly).
this proves my theory that the CTS-V2 is built off the AWD chassis. there seems to be more room in the tunnel area on the right side for the exhaust and fuel lines where the AWD stuff would be. maybe Cadillac wanted the V2 AWD then scrapped the idea later in its development. I know the STS-V is built off the AWD chassis as I know a guy who has one and the tunnel is stamped AWD (just some stupid thoughts I had)…
 

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Discussion Starter · #5 ·
this proves my theory that the CTS-V2 is built off the AWD chassis. there seems to be more room in the tunnel area on the right side for the exhaust and fuel lines where the AWD stuff would be. maybe Cadillac wanted the V2 AWD then scrapped the idea later in its development. I know the STS-V is built off the AWD chassis as I know a guy who has one and the tunnel is stamped AWD (just some stupid thoughts I had)…
After seeing your swap Info I realized mine would be more difficult due to the older donor engine and communication methods. My end goal is to retain complete factory usage of everything( AC, original gauges, etc..). As far at the mounts go I’m at a bit of a dilemma with them. I was able to order the left hand bracket (15234761), but the right one (15234762) is on a national back order from gm and every other legitimate parts vender. I’ve been checking eBay everyday for the last month for one to pop up and still have nothing. I’ve called Atleast 30-40 junk yards all over the country and nobody can see to get me one. So finding that right bracket might be a pretty big hold up for me. If it comes down to it I’ll just have to fab something up for the time being.

I’m happy to hear I’ll have one less thing to worry about with Stock pump. As for the accessories I’ll have to play around and figure out the best possible combination for them. Only other question I have about that is I saw the one AC was a night mare for you. If I were to switch up to a different compressor would that avoid the night mare of that line?

Also as far as the rear end goes, whats the whole situation with that? I’d assume we’re gonna have different Stock rear diffs, but I was wondering If the stock diff would be able to hold the power of the LS?

I agree with you on your theory about the V being built on the AWD chassis. There seems to be tons of room based on some measurements even with the Bulky 4L80.
 

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08 CTS L76/MYC conversion
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i have a set of mounts for another project, they are almost identical. I will dig them out and take some pics and you can make your decision. maybe join the CTS-V forum on Facebook and place an ad for mounts, manifolds and catalytic converters.

i believe Holley makes a high mount A/C system, looks like this.

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the CTS-V uses the basic same rear differential as the CTS, only it’s made from cast iron. Mine has held up without any issues, it will lay some rubber from both rear wheels going into second and chirp going into third.

your 4L80 will use a slip yoke
you will need an adapter for the rear end. Something like the GTO guys use when going to a one piece drive shaft.


dont know if this is exact what you would need but it would be similar…
 

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You may be able to do some things to this engine to make it more compatible but you will need to do some research. You may need the computer from a 2006 truck to even consider to work. In 2006 they still made the same engines but 2006 was the first year the truck had Canbus. You MAY be able to get that to communicate with the computers in your car. 2006 GM trucks had CANBUS for the engine and transmission in 2006. This is the same CANBUS network that is in the 2008 CTS. The MAIN difference between a 2006 truck and a 2005 truck is the whole truck was on the old 1850 network, for the 2006 they kept the non-drivetrain items with the 1850 Databus but the drivetrain was CANBUS. In 2007 the truck had CANBUS for drivetrain and safety features and SWCAN for everything else. The 2008-2013 CTS uses same system as 2007 trucks. SO It is likely you could use the computers, harnesses and sensors for a 2006 truck on your engine and be able to sync it to your car. May require something as simple as HPTuner to program the cars VIN into the 2006 PCM. The transmisison should also work with the 2006 computer as well. The BCM will send out requests to the other modules in the system and ask for a status. It probably won't care about the PCM being different as long as it has the right VIN number. So using the wiring and computer from a 2006 truck could potentially make this install MUCH simpler. Otherwise you might need a crank shaft with the 58 tooth wheel and a newer computer with programming for the older engine. Or a custom after market computer. But I think in the end you may just find a 2006 computer, harness and sensors will work just fine. They atleast are using the same type of databus
 
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good call rod, he could always upgrade to the newer computer to communicate with the 2008 CTS network.
he would need the crankshaft with the 58x or change the ring from 24x to 58x (don’t know if it’s possible or not)
newer engine harness, 58x crank sensor, timing chain cover with cam sensor and correct cam gear, knock sensor
relocation, and prob some other stuff….
 

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Discussion Starter · #11 ·
i have a set of mounts for another project, they are almost identical. I will dig them out and take some pics and you can make your decision. maybe join the CTS-V forum on Facebook and place an ad for mounts, manifolds and catalytic converters.

i believe Holley makes a high mount A/C system, looks like this.

View attachment 612167

the CTS-V uses the basic same rear differential as the CTS, only it’s made from cast iron. Mine has held up without any issues, it will lay some rubber from both rear wheels going into second and chirp going into third.

your 4L80 will use a slip yoke
you will need an adapter for the rear end. Something like the GTO guys use when going to a one piece drive shaft.


dont know if this is exact what you would need but it would be similar…
I joined a few of those CTS-V groups on Facebook and found a couple of V part outs so we will see where I can get with that. If nothing else I'll let you know about those extra mounts you have.

After I get the trans and engine dropped in I'll have to take a look at the drive shaft situation and see what will work out. I'm super happy to hear I can run the stock diff, I was a little worried about one pull shattering the thing to pieces.

In your thread I remember you saying that you swapped the heater core hoses for the V ones. are those the only hoses/ lines you swapped from the v?
You may be able to do some things to this engine to make it more compatible but you will need to do some research. You may need the computer from a 2006 truck to even consider to work. In 2006 they still made the same engines but 2006 was the first year the truck had Canbus. You MAY be able to get that to communicate with the computers in your car. 2006 GM trucks had CANBUS for the engine and transmission in 2006. This is the same CANBUS network that is in the 2008 CTS. The MAIN difference between a 2006 truck and a 2005 truck is the whole truck was on the old 1850 network, for the 2006 they kept the non-drivetrain items with the 1850 Databus but the drivetrain was CANBUS. In 2007 the truck had CANBUS for drivetrain and safety features and SWCAN for everything else. The 2008-2013 CTS uses same system as 2007 trucks. SO It is likely you could use the computers, harnesses and sensors for a 2006 truck on your engine and be able to sync it to your car. May require something as simple as HPTuner to program the cars VIN into the 2006 PCM. The transmisison should also work with the 2006 computer as well. The BCM will send out requests to the other modules in the system and ask for a status. It probably won't care about the PCM being different as long as it has the right VIN number. So using the wiring and computer from a 2006 truck could potentially make this install MUCH simpler. Otherwise you might need a crank shaft with the 58 tooth wheel and a newer computer with programming for the older engine. Or a custom after market computer. But I think in the end you may just find a 2006 computer, harness and sensors will work just fine. They atleast are using the same type of databus
After reading your reply I hopped on an LS thread and found a few people who did this conversion to the newer generation computers. Taking this route will definitely simplify things all around and all I should need to order is a timing cover, chain dampener, 58x reluctor wheel, 4x cam plate, harness, ecm and sensors. I'm going to do some more digging into this and get more details. thank you for the info, it's a HUGE help!
 

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I used heater core hose assembly from 2004-7 CTS-V that fit perfectly.
I used the upper coolant hose from 2009-13 CTS-V. I got from summit (continental brand ($25) I believe.
my lower coolant hose is custom made from the original V6 coolant pipe with a small 90* rubber piece.
you will need a CTS-V front sway bar. The V6 is a strait piece where the V dips down to clear the oil pan.
I picked mine up off eBay for $60 shipped.
 

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good call rod, he could always upgrade to the newer computer to communicate with the 2008 CTS network.
he would need the crankshaft with the 58x or change the ring from 24x to 58x (don’t know if it’s possible or not)
newer engine harness, 58x crank sensor, timing chain cover with cam sensor and correct cam gear, knock sensor
relocation, and prob some other stuff….
I have an LQ9 out of a 2004 that was built up significantly. When ordering the crankshaft I had to specify the number of teeth on the shaft. The 58 tooth wheel just presses onto the crank shaft from what I understood. I would guess the 58 tooth wheel may be necissary for the 2006 computer but I am not sure. I know it is necissary for newer computers. Something important to know before installing the engine. And with the computer from the 2006 It is very likely as long as the vin matches it will talk fine with the car along with the transmission. The BCM doesn't really care what is on the network as long as it talks the same "Language" on the same buss and from what I understand the network protocals did not change until much newer years. Not sure when or if the databus is different. Last I knew GM was working on basically an in car ethernet type network but last I knew it was still just in development.

One thing to consider is if you have to pull the crank shaft to replace the ring to be compatible with the newer computer it might be a good time to consider rebuilding the engine but if I recall it was already being rebuilt if I am not mistaken.
 
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Discussion Starter · #14 ·
I used heater core hose assembly from 2004-7 CTS-V that fit perfectly.
I used the upper coolant hose from 2009-13 CTS-V. I got from summit (continental brand ($25) I believe.
my lower coolant hose is custom made from the original V6 coolant pipe with a small 90* rubber piece.
you will need a CTS-V front sway bar. The V6 is a strait piece where the V dips down to clear the oil pan.
I picked mine up off eBay for $60 shipped.
Perfect, I’ll get the core hose assembly on order then. The lq4 water pump outlet for the upper hose goes the opposite direction so I’m gonna have to swap it out for a g8 pump.
I remembered reading about you having to swap the swap bar. I was able to get one a few weeks ago but I definitely didn’t get it for $60…. Ended up have to pay literally double that. Along with that I also had to swap out the AWD steering rack for a RWD/V one.

I still haven’t heard back from any of the people in these V groups on Facebook. I’m interested in those mounts you have if your willing to part with them.
 

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So, a few months back I was able to pick up a 2008 CTS4 dirt cheap. The original 3.6 had 200k on it and a destroyed valve train as a result of a timing chain failure. The dream of owning a CTS-V has long been in my head, but financially it’s not in the cards. when I saw this CTS4 come up for sale the ideas stated coming and I pulled the trigger on it. I figured it couldn’t be that hard to put an LS into something that already had version produced from factory.

after getting the car the tired old 3.6L was pulled out in the same weekend.


From there the research and hunt for a donor engine began. One of the first things I realized was the AWD front cradle wasn’t going to work if I wanted to drop the LS right in to the factory mounting spots of a V. I was able to get my hands on a RWD/V cradle Out of a local junk yard( I took some measurements and everything is going to bolt Up perfectly). About the same time I found the perfect donor vehicle for the LS. A 2001 Silverado 2500 RWD 6.0L LQ4 paired to a 4L80 that was running and driving with only 85k on it. View attachment 612146
This was more than ideal because I could see it run and have plenty of extra parts to sell off to help fund the build. The 6.0 is going to get alittle love before being transplanted into my CTS. The plan for it now is a mild build with 0.040 cosmetics head gaskets, lifters, PAC trunion and spring kit, a sloppy stage 2 cam, and some other odds and ends.

Things start to slow down a bit now. I was having trouble figuring out some ways to go about things on this build that is until I found these lovey forums. Did some digging and came across the legend of a man who did this swap already @Big_kid. I looked through his swap forum and it was a huge help for a lot of the Process even tho there’s some differences between our swaps. Right now I’m at a bit of a stand still on parts due to me being stationed in Alaska, so parts tend to take awhile to get here…..

While I’m waiting on parts I want to get some other details of swap figured out. Wiring is a huge question for me and I want to take
the best route possible. Another question is the fuel system. Am I able to run the stock pump that’s on it now? I would assume the 6.0L is gonna be a bit more thirsty then the stock 3.6L. Front accessories are another big one, what alternator, water pump, etc should I run? Looking forward to hearing from you guys and keeping you updated on the progress!!
First a moment of silence for that truck that looks like it should have been a second project (restore).
Figure out your drivetrain plans before buying anymore hardware. As has been mentioned, compatibility issues are a grave concern due to generational and year to year changes.

You should decide on the intended engine management before buying performance parts. It's just my opinion, but I believe patience and a hunt for a second gen V engine with harness and PCM would have been a better start for you at your level of familiarity with the computing system, it's just easier to me in the long run to have as much plug and play as possible, having only to deal with VIN matching for successful operation.

You can end up spending as much on parts and methods to defeat the onboard systems as you would using already compatible parts, in addition to the expense of your pending learning curve.

Sites like the one in the attached link may offer some guidance/solutions; In my years of swap madness and nonsense experience, less is more, as in keeping customized components to a minimum is a huge benefit, having had a failed custom made axle and using aftermarket computer interfaces/intercepts to link incompatible speed sensor and gauge signals. It's all good until it breaks, or fails and a replacement takes weeks to arrive and you're hundreds of miles from home.


Keep all of the components removed from the car until you're done, as you're only a working V6 away from a complete, working vehicle. Size up the possibility for an AWD V8 with a pan modification while you have a little down time.
 

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The G8 had two different water pumps (they changed half way through production). I’m using the later style LS3.
the hose outlet is on the right side (looking at the pump from the front) this fits the CTS-V upper radiator hose.
the early G8 water pump has the hose outlet on the opposite side. The LS3 style pump also has the thread bosses
For the LSA/LS9 supercharger belt tensioner. I used one of these bosses for a support for my lower radiator hose…
NOTE: the upper CTS-V radiator hose is super close to the air intake tubing with about 1/4” clearance…
 

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08 CTS L76/MYC conversion
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First a moment of silence for that truck that looks like it should have been a second project (restore).
Figure out your drivetrain plans before buying anymore hardware. As has been mentioned, compatibility issues are a grave concern due to generational and year to year changes.

You should decide on the intended engine management before buying performance parts. It's just my opinion, but I believe patience and a hunt for a second gen V engine with harness and PCM would have been a better start for you at your level of familiarity with the computing system, it's just easier to me in the long run to have as much plug and play as possible, having only to deal with VIN matching for successful operation.

You can end up spending as much on parts and methods to defeat the onboard systems as you would using already compatible parts, in addition to the expense of your pending learning curve.

Sites like the one in the attached link may offer some guidance/solutions; In my years of swap madness and nonsense experience, less is more, as in keeping customized components to a minimum is a huge benefit, having had a failed custom made axle and using aftermarket computer interfaces/intercepts to link incompatible speed sensor and gauge signals. It's all good until it breaks, or fails and a replacement takes weeks to arrive and you're hundreds of miles from home.


Keep all of the components removed from the car until you're done, as you're only a working V6 away from a complete, working vehicle. Size up the possibility for an AWD V8 with a pan modification while you have a little down time.
a complete CTS-V2 drop out on eBay right now.…
I paid $3800 for basically anything I wanted off a totaled G8 and give the seller back what I didn’t want/need…

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a complete CTS-V2 drop out on eBay right now.…
I paid $3800 for basically anything I wanted off a totaled G8 and give the seller back what I didn’t want/need…

View attachment 612504
That's not bad at all for that V dropout by comparison considering it will without question fit and plug right in. I don't know how much is invested at this point beyond what the CTS cost, but I have a pretty good feeling he'll get close enough to $12k to have made it a practical option. I'm just keeping in mind his dream is of a CTS-V and the possible additional expense that might be incurred as a result of what he has to learn about, to make the swap work using a hybrid approach.

If his knowledge base for the task equals, or exceeds yours he'll be in good shape, if not, it's going to cost a lot more, so it may as well come with a supercharger attached.
 

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Hmm, Makes me want to consider grabbing another wagon once I get my house, look for a wrecked V and redo the wagon I get. Grab a newer V front end and combine the 3 cars.. What a project. And would probably be cheaper than me buying a real V.
 

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Discussion Starter · #20 ·
That's not bad at all for that V dropout by comparison considering it will without question fit and plug right in. I don't know how much is invested at this point beyond what the CTS cost, but I have a pretty good feeling he'll get close enough to $12k to have made it a practical option. I'm just keeping in mind his dream is of a CTS-V and the possible additional expense that might be incurred as a result of what he has to learn about, to make the swap work using a hybrid approach.

If his knowledge base for the task equals, or exceeds yours he'll be in good shape, if not, it's going to cost a lot more, so it may as well come with a supercharger attached.
I got the original CTS4 for $700 with a 3.6 that still cranked over but had cooked heads. The Silverado donor I picked up was $2k and I took that route because it’s got plenty of clean parts to sell off allowing for the engine and transmission to almost pay for itself. At this point with most of the big parts in hand I’m in about $1k minus the initial cost of the car and truck. I’m going to do a full rebuild on the lq4 and add some power while I’m at it, but still won’t break the bank. I’ve priced out just about everything I need including that ridiculous shipping prices to Alaska and I’ll be in the swap 5k or less without the vehicle costs. I should be able to make a good bit back on the stock CTS and Silverado parts so there’s a little return there. $12k is a stretch even after my modifications to make it a more compatible engine, but if it came to it 12k is still cheaper than a 2nd gen v.

The truck make look pretty in the pictures but it’s a base model work truck that’s 21 years old. It’s got a fair about of little dings, Dents, and other minor issues. In my mind it’s worth the engine and transmission rather than the truck as a whole.

I’ve got some skills In this area, but I can only hope there as good as @ big_kids….
 
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