Getting ready to instal a 6.2 LS3 and 6L80 into my JK
01-03-2013, 09:14 AM
#91
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I have gone from the Rubi TC with 4:1 to the std 2:72 TC (as the 6L80 can't currently be adapted to the Rubi TC). The calculators show that you end up with the same crawl ration with the 2:72 TC as with the Rubi TC due to the very low 4.27 1st gear ratio in the 6L80. So you give up nothing except have a much better low range TC ratio for faster trails. Though Robbie said he hardly ever goes into 4 Low except when going down steep hills where he wants the additional braking or in slow technical climbs for control. Otherwise there is plenty of power to handle pretty much everything in 4 High.
An interesting thing is that the 6L80 seems to just about have the OD ratios of both the 3.8's automatic and the 6 speed stick. As I recall the auto OD was .69 and the 6 speed was .85. Iin the 6L80 6th gear is .667, closely matching the automatic, and 5th gear is another OD ratio of .852, matching the 6th speed sticks 6th gear.
01-03-2013, 10:01 AM
#92
JK Freak
I am really a diesel freak, and would probably go for the Bruiser Conversions 4BT first, that said, Robbie really impressed me. Glad to hear that Robbie is still making people smile with his LS conversions.
Last edited by doc5339; 01-03-2013 at 10:03 AM.
01-03-2013, 11:58 AM
#93
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I am a two rivers wine junky!
01-03-2013, 01:50 PM
#94
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Robbie seems to be changing his mind a bit on gears and now sees some value in lower gears than 4.10's in some applications. I think 37's, mountains, weight, high altitude operation and trailer towing need more than 4.10's. For a lighter, or low land or flatland JK that doesn't tow 4.10's would be great. It seems there is a fuel milage penalty with going with steeper gears. Best milage seems to be in the 1900 to 2000 rpm range at 70 MPH. I'm going to shoot for 2000 at 70 and 2200 at 75.
I have gone from the Rubi TC with 4:1 to the std 2:72 TC (as the 6L80 can't currently be adapted to the Rubi TC). The calculators show that you end up with the same crawl ration with the 2:72 TC as with the Rubi TC due to the very low 4.27 1st gear ratio in the 6L80. So you give up nothing except have a much better low range TC ratio for faster trails. Though Robbie said he hardly ever goes into 4 Low except when going down steep hills where he wants the additional braking or in slow technical climbs for control. Otherwise there is plenty of power to handle pretty much everything in 4 High.
An interesting thing is that the 6L80 seems to just about have the OD ratios of both the 3.8's automatic and the 6 speed stick. As I recall the auto OD was .69 and the 6 speed was .85. Iin the 6L80 6th gear is .667, closely matching the automatic, and 5th gear is another OD ratio of .852, matching the 6th speed sticks 6th gear.
01-05-2013, 05:52 PM
#95
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Any one have any input on towing capacity of a LS equipped JKU. Can the factory D44 handle a 6.2/6 speed and tow a 7000lbs car trailer or should I just get a GMC truck and sell the JK. I believe the new GMs still have a 8.5" AAM diff and I think the D44 is around 8.75" and I think the pinion bearings are larger in the 44.
Last edited by XJ Jay; 01-05-2013 at 05:58 PM.
01-05-2013, 06:00 PM
#96
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That seems like allot of trailer for a Jeep. I would worry more about the suspension than the axle. I don't even think the hitch is rated for that much weight. But i don't have a hitch so i could be fibbing.
01-05-2013, 08:26 PM
#97
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Any one have any input on towing capacity of a LS equipped JKU. Can the factory D44 handle a 6.2/6 speed and tow a 7000lbs car trailer or should I just get a GMC truck and sell the JK. I believe the new GMs still have a 8.5" AAM diff and I think the D44 is around 8.75" and I think the pinion bearings are larger in the 44.
There are a whole bunch of factors to figure in here. From a power standpoint could a 6.2/6L80 do it? I would say very easily. Would the 44 stand up to it. Damn good question. If you were light on the throttle maybe so. I know unloaded I am afraid to get on the throttle from a dead stop for fear of lunching the rear 44.
My main concern would be the wheelbase of the JK. The longer and heavier the tow vehicle is the better it tows. There is a reason most of the rigs Grandma and Grandpa are using to tow their trailers are Super Cab and Crew Cab trucks. Then there is the issue of brakes. Yeah a 7000 pound trailer will have its own brakes system; but if they fail, then what. The JK brakes are marginal as is.
When I towed my Jeep down to MoTech my tow vehicle was a 2012 Ford 1/2 ton long bed PU. It had plenty of power to do it but I had to stay at 55 MPH the whole way or things got to feeling real dicey. Maybe with a load equalizing hitch and sway stabilizers......
My gut reaction would be don't do it.
01-05-2013, 08:31 PM
#98
JK Junkie
I picked it up today and drove it 500 miles home. What a difference. With the 6.2, the 6L80's low 1st gear of 4.03, and the 5.13's this thing is scary fast. It climbs hills like they aren't there.
The trans is amazing. With the 3.8 engine and auto when coming down from the two summits on I70, heading east from I15, I used to have to use my brakes to keep the Jeep from going to fast. Now, 80% of the time it held back just fine in 6th gear and a few times I used the tap shift to bring it down to 5th (which is amazingly still an OD of .852 - 6th is on OD of .667) and never touched the brakes. When you give it gas it drops gears right now and seems to leap forward. I love the LS engine but this 6L80 is nothing short of amazing.
The cruise works as good as any cruise I've ever used. Even in the hills it hold speed within about 1 mph and a tap up or down yields a 1 mph change.
The 5.13 gears are way too much. I'm on worn KM2's which are a bit smallish and I saw 2300 rpm at 70 mph and 2500 rpm at 75 mph. My next tire is going to be MTR's and they seem to be a full size 37. The calculators indicate that the MTR and 4.56 gears would yield 1987 at 70 mph and 2100 at 75 mph. This seems ideal to me. When I slowed down, due to traffic, and the engine was running between 2000 and 2100 it felt real good; very calm.
I monitored temps on the Scan Gauge and the engine pretty much sat at 192 and the trans ran from 118 to 132.
I've only got 500 miles on it but all I can say is this feels better than any Hemi I have driven. The power is right there, right off ideal and it just feels great. There is no sturm and drang. I have driven both Ripp and Avenger Superchargers and there is no comparison. There is no wait for boost, no dead spots in the power band. The LS engine just seems to love the band from 1500 to 2500.
I could not be happier and recommend the LS and 6L80 conversion and Robbie and the boys at MoTech without hesitation. I'll pst some additional thoughts as they occur to me. I may even post a pic or two if I can figure out how to do it.
The trans is amazing. With the 3.8 engine and auto when coming down from the two summits on I70, heading east from I15, I used to have to use my brakes to keep the Jeep from going to fast. Now, 80% of the time it held back just fine in 6th gear and a few times I used the tap shift to bring it down to 5th (which is amazingly still an OD of .852 - 6th is on OD of .667) and never touched the brakes. When you give it gas it drops gears right now and seems to leap forward. I love the LS engine but this 6L80 is nothing short of amazing.
The cruise works as good as any cruise I've ever used. Even in the hills it hold speed within about 1 mph and a tap up or down yields a 1 mph change.
The 5.13 gears are way too much. I'm on worn KM2's which are a bit smallish and I saw 2300 rpm at 70 mph and 2500 rpm at 75 mph. My next tire is going to be MTR's and they seem to be a full size 37. The calculators indicate that the MTR and 4.56 gears would yield 1987 at 70 mph and 2100 at 75 mph. This seems ideal to me. When I slowed down, due to traffic, and the engine was running between 2000 and 2100 it felt real good; very calm.
I monitored temps on the Scan Gauge and the engine pretty much sat at 192 and the trans ran from 118 to 132.
I've only got 500 miles on it but all I can say is this feels better than any Hemi I have driven. The power is right there, right off ideal and it just feels great. There is no sturm and drang. I have driven both Ripp and Avenger Superchargers and there is no comparison. There is no wait for boost, no dead spots in the power band. The LS engine just seems to love the band from 1500 to 2500.
I could not be happier and recommend the LS and 6L80 conversion and Robbie and the boys at MoTech without hesitation. I'll pst some additional thoughts as they occur to me. I may even post a pic or two if I can figure out how to do it.
Post up a video and show us the power!
01-05-2013, 08:44 PM
#99
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All I can say is that the damn thing is amazing. But I am going to 4.56 gears to drop the rpm on the freeway at 75.
