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Higher horses, higher revs & even higher torque, a streetable LJ engine swap


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toximus

toximus

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I also think it's going to behave differently with the LS which will be providing more torque at all RPMs than the 4.0 and it isn't going to mind revving high where the 4.0 struggled to stay over 2.5k rpms on some climbs and the transmission would be forced to drop a gear. The 6L80 is also going to be an entirely different beast and hopefully won't lose traction as much during shifts. Overall I expect it to be more forgiving of improper gearing.

Whether that means a 3.8:1 or 3:1 ratio is better I don't know.
 
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Indy

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I have a stock 5.3, 4L60E, 4:56 and 35s. I haven't felt the need for 4:1 yet. 2:72 has been perfect for me on rocks like Rubicon, hill climbs and sand. V8 with auto is a completely different Jeep!
 
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I have a stock 5.3, 4L60E, 4:56 and 35s. I haven't felt the need for 4:1 yet. 2:72 has been perfect for me on rocks like Rubicon, hill climbs and sand. V8 with auto is a completely different Jeep!
Good to hear some data points! There's a significant difference between your 4.56 gears and my 5.38s even after factoring in tire size. With the configuration I'm planning on going with, it'd be like me starting in 2nd gear. Which is kind of like what @gaabbee was talking about.
 
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A small update:

Advance Adapters recommended the stronger G2 Pro case for me instead of the Trail series (aka. the "normal Atlas" case). They said the Trail series case is typically for stock applications for up to 500hp and the G2 case for over 500hp (although their recommended horsepower does change based on the weight of the vehicle, and my rig is 4800lbs). My engine is a touch under 500hp and if I ever decide to add more power I'd be looking at 630hp so for a few hundred dollars extra I decided the stronger case would be a worthwhile investment to keep the option of more power available. It's also 7-10lbs lighter then the Trail series and exactly the same physical size externally so there's no downside. They also have an even stronger racing case which they did not recommend for me.

They're also having trouble getting small parts due to coronavirus. They project starting work on my case in 6 weeks and shipping it to me in 8 weeks.
 
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I don't know enough about why but the LS3/480 6L80e kit only comes with the higher 3000-3400k stall speed converter. The LS3 430 comes with the 2400-2800k stall torque converter.
I made some calls and found the answer to why the LS3/480 only comes with the 3000 stall. It has to do with the duration of the camshaft. If a lower stall converter is used, the output (ie. the vehicle) would be jumpy/lunges at slow speeds. The downside is that the converter won't lock up until higher rpms and will cause more heat. The transmission will lock up in overdrive so it won't be an issue on the highway.
 
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I talked to Chris at Circle D this morning and he answered all of my questions about which torque converter to go with for my uses and recommended their 278mm torque converter in 2600-2800 rpm stall: https://www.circledspecialties.com/6...p-series-278mm I'll be able to reuse the stock flex plate.

He mentioned this converter would work well for the stock cam LS3 430 and the hot cam 480 (the one I'm planning on going with) and if I supercharge in the future. It will smooth out the chop from the hot cam so it'll still idle and crawl well at low speeds/rpms. The 278mm converter is 11 inches in diameter making it about an inch smaller in diameter than factory which is where most of the higher stall rpm comes from. The smaller diameter will help to transfer less fluid at idle. This will give less pushing at the brakes, because of the cam. The 2600-2800 stall will allow the pedal to feel connected while not being too tight for the cam. This converter is rated to around 550rwhp or 750rwhp if I upgrade the front cover to billet (which could be good if I boost).

It sounds like Chevy "fixed" the choppy cam by installing their 3000k converter which probably works for 99% of their customers who are installing them into hot rods/drag applications.

Having had no first hand experience, I'm contemplating keeping the 3000k stall in for now and if I don't like it I'll swap it out for the Circle D. That way I'll know why it needs to be changed and gain experience of the difference. It seems like it'd be an easy enough thing to swap on a weekend even after being installed. Unless somebody knows for sure that it's going to be terrible?

What do you guys think?
 

fixmysix

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A couple things I've learned about the 6l80. TUTD isn't always plug and play. There are certain tunes you have to run and various resistors you have to build in to the switches in some cases. There are stand alone modules on the market which allow a simple switch to ground to allow it. I know Mitch at https://www.swaptimeusa.com/ builds one for around $200. You could pair that unit with one of the Lokar shifters which should give you everything you want. Mitch can also program your TCM unless you have someone local. He sends an interface to you so you don't have to pull the pan and the internal TCM and mail it out. He works for a company that does gen IV and gen V swaps in to Jeeps. He's a pretty smart guy and always willing to help in my experience.
 
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Welp, I'm learning a lot!

It's sounding like even though the LS3 480 dyno charts all look great and very usable for a Jeep, the quality of the low range RPMs is choppy and will cause the tires to lurch, breaking traction, as the engine chops. This problem can be smoothed out with a different torque converter (as I mentioned in a previous post), but that only trades for another set of problems that I worry I'll still be fighting with a custom torque converter like the Circle D. Additionally, from what I understand the 480 needs a higher idle (not good for a Jeep application). The stock LS3 430 will behave exactly like a production LS3, idle at 550rpm, and I can use a lower stall torque converter.

I asked 2 of the main companies that do LS swaps into JKs their experience with the 430 and 480: They said the 480 can be done and has been done and took a long time to figure out a decent tune. The consensus from both was that they prefer the 430 for crawling, cruising, daily driving, and what they'd choose for their own. The 480, they said, is fun for spirited driving.

It feels wasteful leaving 65hp and 50lbft of torque on the table, but I'm starting to think I'd only be trying to tame how wild the hot cam wants to be. If the stock LS3 at 430hp isn't enough once I get it installed, I suppose I can use that as an excuse for a supercharger which would keep the slow speed/low rpm crawling feeling like stock but still let the Jeep eat with a heavy foot.

I'm still doing research to confirm all of this before ordering but I'll probably error on the safe side of knowing what works instead of trying to be the first...
 
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I hope I'm not exasperating anyone with my research (if so, you might want to check back in 2 months once the major components arrive)! I know this build thread is a much different pace than my main build thread and shares more thoughts, ideas and concerns rather than solutions like my other thread did. The research is so I hopefully can make things work well the first time.

If I had infinite money to try out different engine and transmission combos it'd be fun to try them all and get answers to my concerns and real world data about which combo works best.

Hopefully this thread will still have great solutions to the goals I outlined in my first post!
 
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gaabbee

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Unless you want to drop another 3g on a ls7 I say go ls3. When you get bored sky is the limit but get it working first and enjoy it a little without worrying.
 

Wildman

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I think your research will help others that might be considering doing a LS swap. The amount of information you have shared I'm sure will help others out. For those that don't care or want to know can just skip over the info they don't want to know.
I would point out that even with the 430HP engine you are gaining almost double the HP you had with the 4.0 even with the SC. I looked around a lot before I found the cam I wanted for my engine. Yes a loping idle sounds good sitting in the parking lot but as you are finding out it isn't practical for wheelin. I've seen guys with some built engines that couldn't get them to work well on the trail. Everyone was standing around looking and listening to it at the parking lot but was then cussing it once on the trail because we were stuck behind or waiting for them to get it up the trail.
 
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I think your research will help others that might be considering doing a LS swap. The amount of information you have shared I'm sure will help others out. For those that don't care or want to know can just skip over the info they don't want to know.
I would point out that even with the 430HP engine you are gaining almost double the HP you had with the 4.0 even with the SC. I looked around a lot before I found the cam I wanted for my engine. Yes a loping idle sounds good sitting in the parking lot but as you are finding out it isn't practical for wheelin. I've seen guys with some built engines that couldn't get them to work well on the trail. Everyone was standing around looking and listening to it at the parking lot but was then cussing it once on the trail because we were stuck behind or waiting for them to get it up the trail.
I'll just have to play a lopey idle over the speakers. That's the real tech! 😅
 
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I stumbled across something interesting!!! I'm not going to be the first one to tuck the 6L transmission on an LJ! I sent him a message and the transmission pan doesn't hang below the frame either. It's a bit of a relief to see that it tucks nicely and the amount of cutting required appears to be acceptable.

cutting-for-flat-skid.png


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105926579_10103889528904819_387972966220404085_n.jpg


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I know you had said Dave's LS motor mounts wouldn't work have you seen these from Rugged Ridge.

A universal plate like that would work. It's the part that extends over to the frame with Dave's that I can't see working. You might remember with my stock frame mounts I had to modify it so the UCA could move upward.
 

Wildman

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A universal plate like that would work. It's the part that extends over to the frame with Dave's that I can't see working. You might remember with my stock frame mounts I had to modify it so the UCA could move upward.
Yes I remember. I just didn't know if you had found mounts yet or not and ran across these. It's going to be interesting to see how everything fits once you set things in there.
 
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So with a new engine, at what point do you think you should have gone 40’s?
When I find that 37s aren't enough. ;)

On my trips so far I have found that tire size isn't the end all be all. Other builds on 37s and 40s were struggling to keep pace with my build and often getting hung up on stuff that I was able to push right over.

If I were to go to 40s, to keep the ideals I've built for, I would have to move the rear mid-arm brackets on the frame back to stretch more wheelbase, the axles would need another 5" WMS, lower the ride height by 1" or so, and I'd have to go with a inner-fenderless front like the Campbell hood to keep uptravel. At that point it'd really be like starting all over.

Even after having the power to turn 40s I still think 37s are an ideal tire size.