8x Series V8 Swaps (7 Viewers)

[EricG]

315/70r17 until recently changing to 37/12.5. No noticeable change between the two really.

I’ve changed to 4.88 and am running through the first full tank now so I don’t know what it will be now. I’ll report back at some point.

If I did the math right, 35's and 4.11 gears have nearly the identical final drive ratio as my donor vehicle. My 33's mean higher cruise RPM. Wouldn't think that would matter so much for in-town driving though.

 

[White Stripe]

If I did the math right, 35's and 4.11 gears have nearly the identical final drive ratio as my donor vehicle. My 33's mean higher cruise RPM. Wouldn't think that would matter so much for in-town driving though.

Here is that tuning shop I heard about that tunes for fuel mileage. I've never used them. Just info for u if u want to research them.

Wester's Garage Custom Performance Tuning

Westers Garage Custom Automotive Tuning

westersgarage.eidnet.ca

 

[Joe Link]

What is the thinking about the 6 speed automatic vs the 4 speed? Are they roughly the same size or does one take more work under the beast to get the 6 speed to fit?

Depends on which 4 speed you're talking about (people have used both the 4L60E and the 4L80E). This is probably my biggest dilemma. I'm ready to start putting stuff together and I still haven't decided on which engine and transmission I'm going to run. I've been researching this for months, I already have an LM7/4L60E, but my gut is telling me to pick up a 6.0L/6L80E. I feel like if I swap in the LM7/4L60E I'm going to have regrets. The cost difference between the engine/transmission combo's is only about $1.5k-$2k once I factor in refreshing (not rebuilding) the LM7 and rebuilding the 4L60E (due to their reliability issues, I won't run a used one in my overland rig).

Based on my research (please correct me if I'm wrong guys), the 6L80E/6L90E is much stronger than the 4L60E, has better gearing, and you can find low mileage units for half the cost of rebuilding the 4L60E. Downsides are that It's also more difficult to program and getting to the computer to send it out for a tune requires removing the oil pan. From what I've seen, it seems like the Gen4/6L80E swap itself (beyond just the cost of the engine/transmission) is more difficult and more expensive. So far I'm leaning toward this PSI kit for wiring/programming if I go with the Gen4/6L80E.

Here is some of my feedback of a 5.3 vs a 6.0. Hope it helps others. My 80 had a stock lm7 with a performance tune. I just swapped in a 6.0. Got my 6.0 with stage 2 truck cam and ported heads locally tuned.(technically it's a 6.1 after the rebuild)It still needs a little tweaking. Fuel mileage already seems better than the 5.3 with the mail order tune. But I need to start a fresh tank to figure mileage. I towed my 3500 lb camper and it's a much better drive with the 6.0. I stayed in the fast lane without much effort. I didn't do any mountain passes yet. The 5.3 did it ok, you could definitely feel the camper back there and had to keep the rpms up more, but the 5.3 is bullet proof and it doesn't mind. I only lost 1mpg towing my camper over mountain passes giving it all she had. After driving the 6.0 around unloaded I have mixed feelings. Is it a rocket ship? No. I am a little disappointed actually in the acceleration actually. I was expecting a huge difference. I am kind of jaded though because I drive quite a few forced induction cars and trucks fairly often. Will it beat a eco boost f150 unloaded? I'm not sure. I think the eco boost would win. If so oh well. A higher stall converter would increase acceleration significantly but there are some negatives to that.

Back to towing with the camper: With the additional torque of the 6.0, it really didn't accelerate much slower at all through first and second gear with the trailer compared to unloaded which is really impressive. 3rd gear is when you notice it's slower with the camper. But I was able to keep 80 or more in od. In fact I have no doubts it could cruise 90mph with the trailer if I wanted. When I tried to accelerate at 75 or so it would drop to 3rd, get to 80 or 85 without trouble, then go to od and cruise along happily. The torque shines here. I also wired up the tow haul switch and that's really nice with the trailer. This current setup is probably about perfect for most people to be really happy. While it will cruise really well with the trailer, a 80 series with a offroad camper doesn't corner well and I had to be careful to not drive like I'm unloaded-the 6.0 would try if I let it. Im glad my suspension only has only a mild lift in this case.

Could I use more power? Always...unless we're talking 700hp or so, that would just get too out of hand. I would say perfect for me would be a 408 stroker. The machine shop talked me out of it. I think that's what I should have done. Or maybe supercharge or turbo the 5.3 but forced induction creates more complexity than I am not really wanting to take most days. But looking back, I would probably have just put a lsa supercharger on the 5.3 just because it's bolt on almost. I didn't realize the snowball of camming the 5.3 monetarily at the time. Basically it started off I just wanted to cam the 5.3 for a little more power. Then I started to think-well if I do that, I gotta either pull the motor, or rip the front end apart. If I do that, I may as well just drop a used 6.0 in and sell the 5.3. So I bought a 6.0 with decent mileage for 1300. I could sell the 5.3 for at least 500, and have a 6.0 for 800 or so. The 6.0 puts out much better torque stock than a cammed 5.3. I decided to pull the heads and inspect the 6.0. It looked normal, but then I thought about how I want to not mess with it again for a long time. So I rebuilt it. Which shot the price overall way up. I probably have 4000 or so all together into the motor with rebuild. Which is about the price of a lsa supercharger kit for a 5.3. Which would give more power than a cammed 6.0 but have additional complexity. Thus why I'm thinking a 408 would be perfect. A 408 is a 6.0 with a stroker crank shaft fyi. It ends up taking the 6.0 360ci engine to a 408ci 6.8 liter engine which would be way more torque. I also could have dropped in a 8.1 but I would need more suspension lift, significant hood mods to fit it. And I don't think emissions laws in my area would allow a 8.1 swap. Anyway cruiser is fine, it's great, it could be more, but I'm not planning on changing it. And I got about 70 or 80hp over the 5.3 and about the same 70 or so more torque over the 5.3. The torque curve is really flat which is good for a cruiser.

I really appreciate you taking the time to write this up, it helps. My first option is to put a cam in my LM7 and run it with the 4L60E. My second option is to purchase a low mileage Gen4 6.0L and a 6L80E. After reading this I'm pretty sure the added difficulty and expense of the 6.0L and 6L80E would be worth it for me. I'm hoping to get as much range as possible, and for that I think the 5.3L might be better than a 6.0L (I've heard mixed things), so I'm looking forward to seeing your MPG notes.

 

[Joe Link]

Kinda surprised nobody has come along and corrected me yet. I've been researching for what seems like forever, but there has to be something I got wrong

 

[White Stripe]

Depends on which 4 speed you're talking about (people have used both the 4L60E and the 4L80E). This is probably my biggest dilemma. I'm ready to start putting stuff together and I still haven't decided on which engine and transmission I'm going to run. I've been researching this for months, I already have an LM7/4L60E, but my gut is telling me to pick up a 6.0L/6L80E. I feel like if I swap in the LM7/4L60E I'm going to have regrets. The cost difference between the engine/transmission combo's is only about $1.5k-$2k once I factor in refreshing (not rebuilding) the LM7 and rebuilding the 4L60E (due to their reliability issues, I won't run a used one in my overland rig).

Based on my research (please correct me if I'm wrong guys), the 6L80E/6L90E is much stronger than the 4L60E, has better gearing, and you can find low mileage units for half the cost of rebuilding the 4L60E. Downsides are that It's also more difficult to program and getting to the computer to send it out for a tune requires removing the oil pan. From what I've seen, it seems like the Gen4/6L80E swap itself (beyond just the cost of the engine/transmission) is more difficult and more expensive. So far I'm leaning toward this PSI kit for wiring/programming if I go with the Gen4/6L80E.



I really appreciate you taking the time to write this up, it helps. My first option is to put a cam in my LM7 and run it with the 4L60E. My second option is to purchase a low mileage Gen4 6.0L and a 6L80E. After reading this I'm pretty sure the added difficulty and expense of the 6.0L and 6L80E would be worth it for me. I'm hoping to get as much range as possible, and for that I think the 5.3L might be better than a 6.0L (I've heard mixed things), so I'm looking forward to seeing your MPG notes.

Maybe take a Tahoe with a LM7 for a test drive and take a Tahoe with the 6.0 6l80 for a drive. That will give you a good idea of what each combo feels like.

 

[Joe Link]

Maybe take a Tahoe with a LM7 for a test drive and take a Tahoe with the 6.0 6l80 for a drive. That will give you a good idea of what each combo feels like.

Good idea. I've been driving my GF's 2005 Yukon with the LM7/4L60E for years now, and compared to the 1FZ that thing is a rocketship (obviously). Parents have a 2010 Yukon with the 5.3L/6L80E, so I'm familiar with the transmission. I'll have to find someone local with a 6.0L.

 

[thatcabledude]

Good idea. I've been driving my GF's 2005 Yukon with the LM7/4L60E for years now, and compared to the 1FZ that thing is a rocketship (obviously). Parents have a 2010 Yukon with the 5.3L/6L80E, so I'm familiar with the transmission. I'll have to find someone local with a 6.0L.

Any trouble with that 4l60 in the 2005?

 

[Joe Link]

Any trouble with that 4l60 in the 2005?

Not yet!

It has around 130k on it and as far as I know it's never been serviced. Two schools of thought have me conflicted on whether it's too late and it'll cause more harm than good or whether she should go for it.

 

[thatcabledude]

Not yet!

It has around 130k on it and as far as I know it's never been serviced. Two schools of thought have me conflicted on whether it's too late and it'll cause more harm than good or whether she should go for it.

Run it till it doesn’t run anymore is what I would do.

 

[Joe Link]

Run it till it doesn’t run anymore is what I would do.

Thanks! That's the way I'm leaning.

 

[thatcabledude]

Thanks! That's the way I'm leaning.

Keep the fluid changed, throw a good cooler and a Corvette servo on it would help.

 

[Tinkertoy]

Depends on which 4 speed you're talking about (people have used both the 4L60E and the 4L80E). This is probably my biggest dilemma. I'm ready to start putting stuff together and I still haven't decided on which engine and transmission I'm going to run. I've been researching this for months, I already have an LM7/4L60E, but my gut is telling me to pick up a 6.0L/6L80E. I feel like if I swap in the LM7/4L60E I'm going to have regrets. The cost difference between the engine/transmission combo's is only about $1.5k-$2k once I factor in refreshing (not rebuilding) the LM7 and rebuilding the 4L60E (due to their reliability issues, I won't run a used one in my overland rig).

Based on my research (please correct me if I'm wrong guys), the 6L80E/6L90E is much stronger than the 4L60E, has better gearing, and you can find low mileage units for half the cost of rebuilding the 4L60E. Downsides are that It's also more difficult to program and getting to the computer to send it out for a tune requires removing the oil pan. From what I've seen, it seems like the Gen4/6L80E swap itself (beyond just the cost of the engine/transmission) is more difficult and more expensive. So far I'm leaning toward this PSI kit for wiring/programming if I go with the Gen4/6L80E.



I really appreciate you taking the time to write this up, it helps. My first option is to put a cam in my LM7 and run it with the 4L60E. My second option is to purchase a low mileage Gen4 6.0L and a 6L80E. After reading this I'm pretty sure the added difficulty and expense of the 6.0L and 6L80E would be worth it for me. I'm hoping to get as much range as possible, and for that I think the 5.3L might be better than a 6.0L (I've heard mixed things), so I'm looking forward to seeing your MPG notes.

I don’t think I can help. I have a L96 with a 6l90 coming....should be here next week or week after. Its all one pullout so I’m hoping I don’t have to reprogram the trans.

but then again if I toss in a cam and a few other things maybe I will. My tear down and swap isn’t really expected to start til Sept so it might be a while before you hear results from me.

 

[Joe Link]

I don’t think I can help. I have a L96 with a 6l90 coming....should be here next week or week after. Its all one pullout so I’m hoping I don’t have to reprogram the trans.

but then again if I toss in a cam and a few other things maybe I will. My tear down and swap isn’t really expected to start til Sept so it might be a while before you hear results from me.

Awesome! I'll add your name to the list of builds I'm following

 

[NeverFinis]

I don’t think I can help. I have a L96 with a 6l90 coming....should be here next week or week after. Its all one pullout so I’m hoping I don’t have to reprogram the trans.

but then again if I toss in a cam and a few other things maybe I will. My tear down and swap isn’t really expected to start til Sept so it might be a while before you hear results from me.

I am very interested in your progress. I was going to put in a reman 1FZ-FE, but looking at V8 swaps. I am specifically looking at the L96 with the 6L80 from a single donor vehicle. I think the 6L90 is a bit longer, but if that is what comes with a donor, then I will use it. 6L90 might require drive shaft modifications due to its extra length. I don't think the 6L80 does. I am still trying to learn. The number of Chevy V8 engines is overwhelming.

If I had my way, a 7.3L Ford Godzilla motor would be the motor of choice. $7K for a new 7.3L crate motor...but a ford transmission to HF2A transfer case adapter doesn't exist. It would probably wouldn't fit anyway but the 7.3L isn't that wide (25.5").

Edited to add that I won't be going with a 6L90 unless a 32 spline output shaft can be sourced, or machined.

 

[Tinkertoy]

I guess I need to start a build thread. Or maybe it should be a disaster thread. Think of it as if you are going to do a swap. Don’t follow this guy thread.

obligatory pic to get peeps excited. And peep that QPM mount box in the background

 

[thatcabledude]

Did any of you LS guys regear? If so, what transmission and what tire size are you running?

Planning on running 35's-37's, I went to 4.88's before I decided to swap and I'm worried I'm going to regret it.

I ran stock gears and 315s with 4l60e for 3 years. Absolutely, totally fine for me. Yes, I live in FL, but I’ve driven/wheeled the truck in CO, UT, etc.

I switched to 37s a few months ago and the truck drove great and I didn’t notice much of a change in acceleration on the street after the bump in tire size, but had not wheeled it yet. Felt good on the interstate and the 1,800ish RPMs at 60mph was nice too. My rear diff was in dire need of rebuilding and I figured I may as well regear. I went 4.88s. I’ll be plugging the 3rds in this Wednesday, so I will be able to let you know what I think really soon.

4.88s are freaking perfect. You won’t be disappointed. My last two tanks averaged just a hair below 17mpg.

 

[Cruiserhead05]

4.88s are freaking perfect. You won’t be disappointed. My last two tanks averaged just a hair below 17mpg.

Crazy. I'm on 37's and 4.88's and definitely don't get close to that.

 

[Tinkertoy]

Crazy. I'm on 37's and 4.88's and definitely don't get close to that.

It was all downhill

 

[thatcabledude]

Crazy. I'm on 37's and 4.88's and definitely don't get close to that.

And I’ve seen people claim 20 on here. I don’t believe it for a minute.

 

[Cruiserhead05]

And I’ve seen people claim 20 on here. I don’t believe it for a minute.

Agreed; maybe in near stock form. I'm sure there are a tons of variables that play into it. You're running a 5.3, 6,0, 6.2? Not sure how much that plays a difference, but assume it could.