2005 LJ engine upgrade

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Robert Bauer

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Honey Brook, PA, USA
So I need a little more power to pull my 2200lb boat around and my 4.0 is good but is not the powerhouse that I'd like it to be. My cousin has a 2001 dodge Dakota with a 4.7L motor in it that recently got totaled in an accident. The engine has a little more than a 100,000 miles on it and has been kept in immaculate condition.
I see a swap in my future with his engine. I searched the net for similar swaps and they aren't the most popular since everyone jumps to the 5.9 hemi engine. I did see a few though and most said the wiring was the worst. I'm willing to do the work and get this in since I'll work on it during the winter.
Anyone have any suggestions?
 
Regear makes no more power and you already have 3.73... Not sure about how much you gain tho going from 4.0 to 4.7..... I'd think a super charger is the easiest way to gain horse power.

But then the 4.7 is like free ........
 
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Robert Bauer said:
That would be in the works too. But the engine would be a nice early winter project. Then I can look for gears later in the winter.


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Horsepower can't make up for improper gearing. I would regear immediately considering you have 35's. If you still have stock gears with 35's it is no wonder you feel that the 4.0L is underpowered. If you still need more power after regearing, then engine swap.
 
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jodomcfrodo said:
Horsepower can't make up for improper gearing. I would regear immediately considering you have 35's. If you still have stock gears with 35's it is no wonder you feel that the 4.0L is underpowered. If you still need more power after regearing, then engine swap.
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What should I regear to?



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Robert Bauer said:
What should I regear to?



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That depends on a few things. Firstly, what transmission do you have? Secondly, what engine do you have? (guessI I can safely assume 4.0 from the thread though...)
 
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jodomcfrodo said:
That depends on a few things. Firstly, what transmission do you have? Secondly, what engine do you have? (guessI I can safely assume 4.0 from the thread though...) Another thing to take into consideration is what rear axle you have.
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The axles are stock. 3.73.
It’s a 4.0 with the 42RLE transmission.

So if I regear what’s the cheapest way to get the parts? What other vehicles can I rob them from?


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Robert Bauer said:
The axles are stock. 3.73.
It’s a 4.0 with the 42RLE transmission.

So if I regear what’s the cheapest way to get the parts? What other vehicles can I rob them from?


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You need 5.38's if you have a dana 44 rear end (you have an LJ so you have a dana 44 as far as I'm aware). 5.38 is essentially as low as you can go and you can not rob those gears off of any vehicles as far as I'm aware. I don't think any vehicles come with 5.38's stock.

An automatic, 35's, and 3.73's has got to be absolutely atrocious in terms of power. You'll have a completely new Jeep if you regear.

EDIT: As @Rob5589 mentioned below, a front dana 30 is what limits you from going up to 5.38's, not a rear dana 35 as I implied above. Get 5.13's unless you have a Rubicon. Again, disregard what I said here. I think I need some sleep....
 
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Robert Bauer said:
The axles are stock. 3.73.
It’s a 4.0 with the 42RLE transmission.

So if I regear what’s the cheapest way to get the parts? What other vehicles can I rob them from?


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Oh wow ! With the 42RLE The jump from 3rd to 4th is extreme. But I'd gear assuming when towing I'd lock it in 3rd, turn off the OD and only use OD when not towing.
 
If not a Rubicon, the lowest you can run is 5.13. And that is what you need with your set up. Hell, 3.73's with 35's have to be terrible when not pulling a boat.

There is no robbing of parts, unless you somehow find a 5.13 geared Dana 30/44 combo laying around. Not likely.
 
Definitely re gear. And the 4.7 swap is rare bc it doesnt have much if any aftermarket support for swapping. You would be better off selling the Mopar 4.7 and funding a Chevy 4.8 or 5.3 swap from a GM vehicle. It would be a lot easier on the wallet and the head if you swapped it in.
 
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The jeep gets up and goes from the start on normal driving but gets really shitty around 55 and up. I have to turn the overdrive off to get any power.
I looked and have a Dana 44 in the back and a Dana 30 in the front. What’s a good gear set to stay with what I got?


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Robert Bauer said:
The jeep gets up and goes from the start on normal driving but gets really shitty around 55 and up. I have to turn the overdrive off to get any power.
I looked and have a Dana 44 in the back and a Dana 30 in the front. What’s a good gear set to stay with what I got?


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You are describing a scenario where a re-gear is the solution. A re gear will get you back in overdrive. However, the 42RLE typically hunts for overdrive and shifts too early which brings drivers attention to it often. The only solution is to regear to something like 4.88 or 5.13.
 
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With that trans. and 35,s, and the front Dana 30, it's not possible to gear it correctly. 5.13 is the limit. You could go with those gears, and go to 33,s.
 
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Taylo1 said:
This is the set I'm going with in a 5:13 setup. https://www.quadratec.com/products/52466_001X_PG.htm.
Except I have a rubicon.
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Since I can’t go to 5.13 gears with what I have I’ll probably go to 4.88. The set you posted looks good. I’ll have to wait a bit to do it since all the summer fun has taken its toll on my bank account. Especially since I bought a boat. But the engine swap might still happen.


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Robert Bauer said:
Since I can’t go to 5.13 gears with what I have I’ll probably go to 4.88. The set you posted looks good. I’ll have to wait a bit to do it since all the summer fun has taken its toll on my bank account. Especially since I bought a boat. But the engine swap might still happen.


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Don’t go with G2. Go with Revolution gears. I highly recommend them.
 
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