Motech swap questions with Gen IV 480hp LS3 crate engine

scrhino

New member
I'm running 60 front, Sterling rear, and 41.5" Pitbulls. For the crawling we do, I would like to run the numbers on a 4 speed if the computer doesn't have a problem with it(?).

Eddie has a different primary use case being in Nevada. You're from Auburn - ever go to Chocco? The guys I've seen do Boatramp have been ultra low geared going slow and I've seen bouncers throw big HP at it and not make it.

Motech - thanks for the overview. Sounds like both of y'all agree 5.38s would be ok, if a little torquey, with 40-42s. I may just want to swap out or regear(if possible) the Atlas. Figured I would need to change the input, maybe just do that and see how much I like/hate it and go from there when the time for the conversion comes.

Thanks!

I live at nearly 6k feet in northern AZ, and frequently drive long, steep mountain grades on I17 in AZ, so I'll for sure be staying with the 5.38 gears in my Dynatrac axles. By swapping in the 241J with the 2.72:1 low range I'll be just fine offroad. If I ever break the xfer case or adapter I'll go to an Atlas II.


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Based on what motech is saying I may switch to the 3.0 Atlas or just stick with my 2.72. Hard to know exactly what is the best route to take.

Never been to Choco but been to windrock several times.

 

RMC2

Caught the Bug
You guys make me jealous. Good luck with the swap. If I could only win the lottery. Gotta buy a house instead.

Liston, you sending your jeep to ORE or doing it at home for the axle swap?
 

Basscat

New member
With the proposed engine/trans in this thread (430/495 6l80), what gearing does Motech recommend for Atlas TC and axles? I have 5.38 in my axles and a 4.3 Atlas II currently in my 2014 3.6l. Wondering if it would be worthwhile sending to AA to redo the current Atlas or buy new. Anyone run a 4speed? I also have a PSC pump/hydro assist already and appreciate the early info.

You'll want to change the gearing in your Atlas to 3.8 or 3.0. If cradling is what you do most go 3.8. If driving fast off road do 3.0.


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2011jk

Member
Gearing in the TC should be checked in relationship to the trans gearing , axle gears and tire size...I played for hours using Grimmjeeper gearing calculator before I decided on 5.38's and a 3.8 Atlas.

Your result will will be whats best you.
 

MOTECH

New member
The Alt bracket pulleys....JK's or Chevy's or ??

We support both the GM and JK accessories, I feel the stock JK accessories with our billet brackets are the best choice.

With the MoTech billet brackets the accessories go back where they were using the stock hoses, lines and electrical connectors; in addition, there are no interferences with the steering gear, frame rail or UCA like there can be with the GM drive.
 

2011jk

Member
Yes but do you use the JK stationary and groved pulleys or the LS truck ones for the Alt bracket when using a JK Alt?
 

MOTECH

New member
Yes but do you use the JK stationary and groved pulleys or the LS truck ones for the Alt bracket when using a JK Alt?

One smooth and one grooved 75mm.

Dayco 89115
Dayco 89144

The smooth pulley is the same idler pulley the 3.8 JK runs. If you had a belt that was a little long you could substitute a 90mm pulley.
 

Basscat

New member
TBH I like the LS3 430, I prefer the drivability over the 480 HP engine. We find the LS3 430 HP engine has about 450 HP at the crank and will outperform a stock 6.4 Hemi when running a 6l80 transmission.

The 6l80 is a strong transmission and it is unlikely you will break it even with a supercharged LS, we have run them in 700 HP engines with no problem. Our 6l80-241J TC adapter is good to 500 HP, we have many running behind the 495 engine. The Atlas 2 is a good choice if you need it - 2WD low and front wheel drive. If you don't need an A2 the 241J works great. I do not recommend(and neither does Advance) the Atlas 4 or the 241OR TC, they don't deal well with the torque. We also support the 6l90 transmission but realistically I would not run a 6l90
unless I already had one.

Stock 44 axles can hold up well with a 6.2 engine with tires under 37", if your running larger than 37's you want to beef up your stock axles or go with some 60's or... I like the D80 rear and D60 front combination. I have 80,000 miles on my stock 44's with a 6.2 with no issues because I drive conservative and that is what matters, you can break axles with a 3.8 in low range if you drive like a gorilla. But for the most part if running a 6.2 with 40's beef up the axles, if running 35" or smaller tires you can get away with the stock axles.

We have recommended gearing and you shouldn't gear an LS like a Hemi or V6. The diverse gearing of the 6l80 means you can launch hard with a 4:1 first gear and cruise at low rpm with a 2cd OD of .66. This means you can run 37's on 4:10's and still get reasonable performance. For general driving(both off road and highway) we like to shoot for a 2,000 rpm cruise speed at 70 mph. This gives you good off road performance with a 3:1 TC and good economy on the highway. So for general guidelines:

35's - 4:10's
37's - 4:56's
40's - 5:13's.

Now the LS is tolerant to gearing due to the 6l80 transmission and lots of torque. If towing or you live in the mountains of Colorado go up one gear size, so 4:88's with 37's instead of 4:56's. If you do mostly highway driving go down one gear size, so 4:10's with 37's instead of 4:56's. Do not go too low on the TC ratio unless you have a need. A 3.8, 4 or 5:1 TC is great on a rock but sucks on trails. With a 4:1 TC your screaming the engine in 6th gear to go 15 mph down a trail and with the torque of the LS you don't need to do that.

Really good advice right there!

I'm running PR80 rear / XD60 front, 40" tires, 5.38s, 3.8 Atlas. Cruises at 70mph / 2,100 rpm. Runs very strong in the Colorado mountains (live in Durango). Engine is 6.2 LS3 (450hp) with 6L80. Excellent combo in all conditions both on and off road. Very low first gear when technical crawling but strings out well with 6L80.


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NecessaryEvil

New member
Really good advice right there!

I'm running PR80 rear / XD60 front, 40" tires, 5.38s, 3.8 Atlas. Cruises at 70mph / 2,100 rpm. Runs very strong in the Colorado mountains (live in Durango). Engine is 6.2 LS3 (450hp) with 6L80. Excellent combo in all conditions both on and off road. Very low first gear when technical crawling but strings out well with 6L80.


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How does your set up do with trail riding?


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nmwranglerx

Caught the Bug
Really good advice right there!

Runs very strong in the Colorado mountains (live in Durango). Engine is 6.2 LS3 (450hp) with 6L80.

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This is what I want to hear about. We do a lot of drives up into southern CO and , hell, even good portions of NM where the 3.8 on 37s totally sucks on the freeway because of the elevation and mountain passes. It makes freeway driving in the JK so unpleasant even with 5.13 gears. Have you driven the LS along the million dollar highway up from Durango to Ouray? How does it handle those steep long grades?


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Extremneon

New member
Right now also accumulating the parts to do a ls3 swap, great thread.

I have 2016 Camaro SS 6L80E trans with 137 miles on it sitting the garage. I have also picked up most of the odd and ends for the swap like, CTSV accessory drive, trans cooler, adapter plate, o2 sensors, COM, etc...

Still have to pickup the motor, atlas and the install kit. Next up is the Atlas II transfer case.


 

Basscat

New member
This is what I want to hear about. We do a lot of drives up into southern CO and , hell, even good portions of NM where the 3.8 on 37s totally sucks on the freeway because of the elevation and mountain passes. It makes freeway driving in the JK so unpleasant even with 5.13 gears. Have you driven the LS along the million dollar highway up from Durango to Ouray? How does it handle those steep long grades?


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Drive it all the time. Live in Durango. LS3/6L80 is a perfect combo for the mountains. The gear spread and propensity to stay in gear and not downshift is the key. 450hp doesn't hurt either.


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