1982 GMC Sierra LS3 + 6l80e 4x4

[cumminclouds]

Like the title reads I am considering starting a swap, I am looking into a moderate LS3 + 6l80 4x4. With the 1st gear of the transmission being 4.06 and the 6th being .66 I am going to put a 3.06 ratio in my diff.... The new Camaros with a LS3 weigh in around 4,000lbs. my truck with a full tank weighed in at 4,800lbs. Would I be able to get good MPG (14-20) and would it still have good enough power to get off the line quick. By moderate I mean cleaning the throttle body + a good tune.. I typically ride on the interstate around 80 and am looking at trying to make it a road trip truck. Thanks

[68GMCCustom]

Do you need an LS3? How about something smaller if fuel economy is a concern. Like a 5.3/6L80e 4x4 combo?

[gchemist]

You'll have plenty of power.
LS3 specs: http://www.camaro5.com/forums/wiki.p...specifications
But, MPG will be hurting as a daily driver in traffic. Even at highway speeds, a 4X4 is a brick. Even with tuning and mods, mid 15's MPG is what I would expect.

[cumminclouds]

Kurt.
I can get the LS3 at a local salvage yard with complete accessories for cheap but I have procrastinated and been letting it sit there for awhile. I looked at the 5.3l for awhile but I wasn't seeing many benefits of MPG, just a loss of power but I haven't looked into it as much as I should've.

Gerado
15 would be on average is what your expecting? Is that city/hwy and would I be better off to look for a L92 out of a escalade or something, or get a cam for lower end torque in the LS3?

[gchemist]

I assume the LS3 has variable engine displacement. If it does, the torque of the LS3 may push it above 15 MPG. I'm really guessing here. I've never done an LS conversion. I base my info on drivers I know that drive late model trucks and suburbans. My sisters Delani (full size) without variable engine displacement can barely manage 16 MPG fully loaded at highway speeds. It's a 6.0 engine. I think your combo can manage that milage. I don't the extent of possible programming with variable displacement engines. I've read that 5.3s respond very well and add milage and power on non variable displacement engines.

[cumminclouds]

Originally Posted by gchemist

I assume the LS3 has variable engine displacement. If it does, the torque of the LS3 may push it above 15 MPG. I'm really guessing here. I've never done an LS conversion. I base my info on drivers I know that drive late model trucks and suburbans. My sisters Delani (full size) without variable engine displacement can barely manage 16 MPG fully loaded at highway speeds. It's a 6.0 engine. I think your combo can manage that milage. I don't the extent of possible programming with variable displacement engines. I've read that 5.3s respond very well and add milage and power on non variable displacement engines.

I've talked to multiple different people and had 1,000 ideas. I talked to a guy named steve with advanced adapters he told me that a 205 transfer out of a 86-91 chevy would work on a 6l80 like spencer said. Also the guy at advance adapters told me if it was him he would do a 5.3l like gerudo + kurtmentioned. He told me that 15 was a good # to aim for out of the LS3 so I asked him about the 5.3 and he also said 15? So i am looking at 15 regardless from what I have been told from different people!!! Finally got the transfer case figured out, still trying to find out if it will get the MPG I was hoping for...

[cumminclouds]

Gerardo
I believe so, I had a chance to buy my work truck I ride in everyday from the place I work at, it has a 2005 6.0 vortec like your sisters truck I have tried to get good MPG out of it but the best I have ever gotten was 14 and the worst would make you laugh... So should I look more into the 5.3's in your opinion? I have done minor searching and havn't seen too much positive but that was minor searching. You were right about it having power, I looked at the link you sent it rates the LS3 at 420/553 when I had a stock 454 in my truck that was 240/355... That torque will help alot

[cumminclouds]

http://www.novak-adapt.com/knowledge/gearing.htm
I entered having having a 3.73 diff., and 1st gear transmission of 4.06 and .66 overdrive and it said I would be running around 2,000rpms at 80. That is in a good range for that motor..

[gchemist]

Ask the motor forum what people are gettng with LS conversions. Do a search? I'm sure owners have posted info here. A guy on another board with a 5.3 gets 20 MPG on the highway SWB and highway speed.

Remember, these trucks were aero dynamically designed for 55 MPH for 81 and up trucks. Adding speed adds resistance. 70 MPH is achievable with decent milage. MY ZZ4 can manage 18.5 MPG with a bed cover and drop. RPM ~2000. With FI, I bet you can match those numbers with a matching drivetrain for the ECM. City driving, forget about it but variable displacement will help.

[cumminclouds]

Sorry to keep botherin you with questions but do you know how much your truck weighs Gerardo and what transmission do you have? I like that setup you have!!

[gchemist]

Originally Posted by cumminclouds

Sorry to keep botherin you with questions but do you know how much your truck weighs Gerardo and what transmission do you have? I like that setup you have!!

I run a ZZ4, custom 700R4, 3.08 gears, 255/60R15 tires, aluminum wheels, and bed cover. Added stuff: ram air setup through 81/82 bumper, electric fans, all external chrome/moldings removed, ~5/6 drop, RPM airgap, 1406 carb, Camaro 3/4 length headers, X-pipe, no cats, dual Magnaflow mufflers, and serpentine belt drive.
Weight: unknown. Probably under 4000 with all the weight of engine bay reductions.

The ZZ4 makes over 300 ft/lbs of torque above 1500 RPMs. Torque is what moves the brick down the street!! You want max torque possible at cruise speeds.

[spencer_41188]

that trans is a little new for passenger drop transfer case may need to use a divorced transfer case out of a dodge inless you can find an adapter for that trans to your transfer case or try to find a 1988 to 1991 np241 pass drop you may have to do some reserch on that see if it will bolt up inless you wana run a ford or dodge axle in front

[cumminclouds]

Spencer
Could I use a electronic transfer out of a newer truck? Or would it not be capable hooking up in my truck?what is your opinion on what I should run? I feel confident about my motor/transmission Choice but have been wondering if I should attempt a electronic transfer case and if it is a passenger side split?
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[spencer_41188]

Originally Posted by cumminclouds

Spencer
Could I use a electronic transfer out of a newer truck? Or would it not be capable hooking up in my truck?what is your opinion on what I should run? I feel confident about my motor/transmission Choice but have been wondering if I should attempt a electronic transfer case and if it is a passenger side split?
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yea no luck with that the only t case that will bolt to the 6l80e other then what belongs on it is a np231 and they go behind a v6 ... i dont baby my truck wouldnt last long for me

find a ford/dodge solid axle ford you will have to move the perches and dodge you will have to cut off the 4link and weld perches on or get it built for your truck by an axle company like curry or crane and this way you can keep the king pins

[cumminclouds]

Originally Posted by spencer_41188

yea no luck with that the only t case that will bolt to the 6l80e other then what belongs on it is a np231 and they go behind a v6 ... i dont baby my truck wouldnt last long for me

find a ford/dodge solid axle ford you will have to move the perches and dodge you will have to cut off the 4link and weld perches on or get it built for your truck by an axle company like curry or crane and this way you can keep the king pins

I've been looking haven't seen much, just where people get custom adaptors for there 205's...... Aiming for a good overdrive and not a slug off the line what is my next transmission in your opinion?

[solanistec]

I have a 06 vmax truck that is my daily driver. With the LQ9 6.0 it gets 16.5 mpg at 70 mph with 3:73 gears and factory 20's. Around town i average 13mph. I want to swap one of these in the 81 some day.

[cumminclouds]

Originally Posted by solanistec

I have a 06 vmax truck that is my daily driver. With the LQ9 6.0 it gets 16.5 mpg at 70 mph with 3:73 gears and factory 20's. Around town i average 13mph. I want to swap one of these in the 81 some day.

Wow that is way better than any of our work trucks! Ours are 2wd so I figured it had no excuse to get as bad as mpg as they do. Have you ever looked into the L92 that was in newer escalades and denalis i believe?

[solanistec]

Originally Posted by cumminclouds

Wow that is way better than any of our work trucks! Ours are 2wd so I figured it had no excuse to get as bad as mpg as they do. Have you ever looked into the L92 that was in newer escalades and denalis i believe?

Stock it is 10:1 compression at 345hp. Was told to use L92 heads, a mild cam and tune will get me near 500. Mine is 2wd, 4wd has 4:10's in that year.

[chebyshortbox65]

Be prepared to spend a lot of money I'm in the process of installing an ls3 and 6l80 in a caprice now make sure you buy a complete engine trans and harness as there is no one that makes a controler and the trans has its own ecm inside the trans and talks to engine computer to set shift points and such and you will have to run a body lift or cut the floor they are big manna Kannada
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[cumminclouds]

Originally Posted by chebyshortbox65

Be prepared to spend a lot of money I'm in the process of installing an ls3 and 6l80 in a caprice now make sure you buy a complete engine trans and harness as there is no one that makes a controler and the trans has its own ecm inside the trans and talks to engine computer to set shift points and such and you will have to run a body lift or cut the floor they are big manna Kannada
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http://www.hotrodlane.cc/
http://www.sporttruck.com/techarticl...e_engine_swap/

[cumminclouds]

One of the local machine shops told me to swap a 89-91 cummins into it.. He said it will be slower than the setup I want but will get great MPG and will be way more reliable/cheap/easier/ and efficent than a LS3...

[Firebirdjones]

Originally Posted by cumminclouds

Like the title reads I am considering starting a swap, I am looking into a moderate LS3 + 6l80 4x4. With the 1st gear of the transmission being 4.06 and the 6th being .66 I am going to put a 3.06 ratio in my diff.... The new Camaros with a LS3 weigh in around 4,000lbs. my truck with a full tank weighed in at 4,800lbs. Would I be able to get good MPG (14-20) and would it still have good enough power to get off the line quick. By moderate I mean cleaning the throttle body + a good tune.. I typically ride on the interstate around 80 and am looking at trying to make it a road trip truck. Thanks

I'm not sure how efficient the LS3 would be for you but shouldn't be much (if any) worse than the 6.0 I used.

The 6L80 idea sounds neat, with the low first gear you could run that high rear gear you mention and still squirt around town nicely and maintain low highway rpm in overdrive. Your issue might be an adapter for the transfer case though....keep in mind.


I did a 6.0/4L60E swap in my 72 blazer 4x4. The 3.06 first gear helps it get moving, and I ran 3.07 rear gears for a while along with 33" tires, wasn't bad really for a 4600 lbs truck. I wanted more squirt so I swapped both diff's to a 3.73 gear. It lays rubber, runs strong, and I consistently get 17 mpg around town and 22 mpg highway. It's not a variable displacement engine,,,just a very sharp tune by yours truly. It's my daily driver as well as our family SUV and vacation vehicle, so I also had long road trips in mind when I built this thing.

It cruises along very nicely at 75 mph....Could go 80 I guess if you wanted to but 70-75 is fast enough for me

You could probably do better on MPG than mine if you went with the 5.3 since there is a sizable difference in cubes (325 vs 364) but I wanted the grunt from the 364 and I knew with tuning I could squeak some mileage out of it anyway....Guys telling you 15 mpg tops are probably running stock tunes that need some serious tweaks. The stock truck tunes in these things suck,,,,,badly.

[cumminclouds]

Firebirdjones
That is what I am aiming for out of a swap. Your MPG and decent power...
What year or type of vehicle did you get the 6.0 out of? My work truck gets terrible MPG no matter what !!

[Firebirdjones]

Originally Posted by cumminclouds

Firebirdjones
That is what I am aiming for out of a swap. Your MPG and decent power...
What year or type of vehicle did you get the 6.0 out of? My work truck gets terrible MPG no matter what !!

The 6.0 is an LQ4 out of a 2004 3/4 ton pickup. The 4L60 is out of a 2005.

I originally had the 4L80 along with the 6.0 but it just wasn't going to work for my swap (longer trans that would have required I move the transfer case,,,that wasn't going to happen) Stout trans,,,,but it also takes more HP to turn it and that was also in the back of my mind.

So the 4L60 was the better choice for me (built to take the abuse) had a better 1st and 2nd gear ratio,,,and also has more overdrive (.70 vs .75 on the 4L80).

I also did alot of other little things for MPG that add up. Things like dual electric fans (no mechanical fan, robs power), I have 33" tires but I kept the width narrow for less roll resistance (10.5") and also kept the tread pattern mild for less roll resistance (BFG all terrains). Lighter weight aluminum wheels, a good intake and exhaust system, some other little things,,,but alot of the MPG was found in the tune.

I removed the MAF and went SD tune, better throttle response, one less electronic gadget too , alot of tinkering with the throttle tables, dialing in the fuel tables with a wideband, and lots of changes in the timing tables. timing tables in the stock tune flat stink with single digit numbers, and alot of timing retard features that can be tweaked to keep mileage consistent. Then to top it off I adjust the DFCO tables to make them more active as they are almost non existent in the stock tune (fuel cutoff when decelerating).

Lots and lots of things can be done in the tune It takes my truck from a gas user to a much more economical vehicle that's easier to accept as a daily driver,,,and picks up 30 hp to boot.

[MTCK]

I'll be watching this one.
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