So, after taking the wife and family on a four-wheeling adventure this summer (Black Bear Pass in Ouray, CO and Top of the World in Moab), the wife has given me the proverbial "green light" to eventually convert the Jeep to a fully capable expedition vehicle. No, this transformation won't happen this year, or even next, but over the course of 2 to 3 years. While I'm not going to build a "bouncer," I will be building a very, very capable rig. I've got a couple of questions though as I'm in the budgeting and planning stages.

1.) The Jeep will be getting a V8. No questions asked and hands down. While I know there are full wiring kits available for the Hemi transplants, I would rather go with an LS engine, mostly for reliability, price (LS engines are generally cheaper than the equivalent Hemi's) and fuel mileage. And before anyone goes off on "you drive a Jeep, don't worry about mileage," remember that this vehicle's purpose will be for long durations off-highway as well as potentially long trips on the highway. Now, with that out of the way, my question is simple - Does anyone make a full wiring harness and/or ECU that retains all of the "stock" functions from Jeep while integrating the LS engine? On a side note (and I'm still verifying this), I want to keep the Jeep street and smog legal. As of now, Colorado deems the JK a "car" (sacrilege right?) and therefore, I believe, the donor motor has to come from a car. Therefore, while the Vortec engines are technically LS-series engines, they would not be in selection pool. And since the Jeep is a 2011, it will almost definitely have to be a Generation IV engine.

2.) I'm pretty well decided on using a TH400 for the transmission. However, with the need for long, over the highway trips, I would like to have an overdrive, which the 700R4 has. However, the TH400 is a stronger and better supported tranny that doesn't take nearly as much HP to turn. On the flip side, I'd also like an underdrive as well. Is is possible to set up a TH400 with both external, aftermarket OD and UD? I know the tranny setup will be long and I might be better off length-wise using a 700R4 plus an aftermarket UD but I'm just curious. I intend to use a twin-stick Atlas T-case behind the tranny.

Thanks in advance!

 

skip the th400 or th700r4, you are going to want to run a 6l80e,4l60 or 4l80, the 6l80 is a 6speed the other 2 are 4 speeds. there are multiple companys that make complete swap kits including harnesses and mounts to put just about any LS and auto trans combo you can think of. Check out Motech I believe they are in Vegas and they build some very quality stuff also Novak, I have heard of people having issues with them but I know of a local shop that did a swap from them and said it was super simple and they had it done in 2 days (motor was already out) with everything working properly

 

Motech has a full a kit but it doesnt use a TH400. 6l80 is what you want for an LS Swap.

 

I think Brusier industries is another. They can also put a desiel engine in. One non turbo and turbo that make like 300hp and 700ish ft.tq. But, not sure if street legal!

 

Thanks. The only reasons I was thinking the TH400 was for simplicity's sake and the durability. I've looked into the 6L80 and the 4L80 as well but was concerned about the durability. I've looked at Motech but as far as I've seen, they don't guarantee meeting emmissions. That wouldn't be an issue if I had a 1980's CJ but with a 2011, I've pretty much gotta be spot on.

 

I've thought about a diesel but weight is the big decider. Well, that and emissions. I'll have to do some more digging on CO engine swaps but I think emisssions is what will keep me from doing it, regardless of weight. Emissions aside, I'm probably reasonably limited to a 4BT. I've heard of a 6BT being squeezed in but the radiator I think was relocated to the rear (not an option for me) and it was still a much tighter fit than even the biggest Hemi out there. The problem with the 4BT is that most of them were made for industrial and emissions-exempt applications. And even the emissions compliant ones shake like grandma with palsy and epilepsy. There's a guy in UT that builds and balances them so that there's basically no vibration from them but he's $$$$$. And while it'd be a sweat conversion, I just can't justify that on basically a North America only expidition rig. If I had plans on shipping the Jeep over to Europe or Africa then diesel would be a no brainer. But since gas is more available in the US and Canada and equally available in Mexico, it just doesn't make sense.

 

Several 6BT swaps have been done. I think all of them required some major cutting into the firewall.

As for emissions, its best to get to know an emissions tester early and let them know what you plan on doing. Work with them to make sure you wont have any roadblocks.

 

I come from the fbody world, I would avoid the th400 based on your gas mileage statement, while it is an incredible trans for drag racing, unless you drop $1400 on the gear vendors overdrive you will get shit gas mileage, and the 4l60 is not a tough trans in my experience, I blew up 3 with my car and it wasn't too heavily modified, the 4l80 and 6l80 transmissions are going to be the ones you want, they're both incredibly powerful and will get you the gas mileage you need with the 6l80 being the best. For more info on them go over to ls1tech.com and go to the automatic transmission stickies, good luck with it, and I love the fact you chose an ls1, ls series motors are pretty incredible motors

 

I probably didn't state my initial diesel response properly. I'm not saying that a 6BT can't be done. Project Rattletrap is a prime example. And if I had $100K to throw at a shop and say build it, well, I probably wouldn't be on this forum asking questions LOL. But I plan on doing this conversion myself in the garage at the house and everything that would be needed for the diesel swap is just more than I want to get into for my first swap. As I get closer, I'll hook up with one of the emissions testers and talk it through with them. Unfortunately, CO keeps changing emission laws pretty much each year so we'll have to see as we go.

 

Thanks for the heads up on the TH400. I was doing some research on the 6L80 and was really amazed at the first gear ratio. 4.02! Wow, that's low. Apparently, there's also a 6L90 available as well that takes GCVW (Jeep+trailer) from 14,000 lbs for the 6L80 up to 21,000 lbs with the 6L90. Now, I'm not saying I'd probably ever even get near the 14,000 lbs rating for the 6L80, but curious if it's worth going after the 6L90 just for strength and longevity. I'm even questioning an underdrive now if I go with a 6L80/90. I'm planning a 4-speed Atlas and probably 4.88 gears. So, without the underdrive and assuming I get the lowest range Atlas, I can theoretically get a crawl ratio of 229:1. I just can't see considering my setup with probably 37" tires needing anything more.

As for the LS choice, I've never been a Hemi fan anyways. They had their day about 30-40 years ago but technology has come so far that it's so much more than just the cylinder head design now. The only other gas engine that has even crossed my mind is the new Ford turbo'd EcoBoost V6's. The 3.5L EcoBoost is generating 365 HP which most likely would be plenty for this setup. And considering it's a V6, it's probably an easier swap, size wize, than a V8. But I would have to deal with a turbo which I'm not a huge fan of either. I'd rather have a supercharger than a turbo.