Making my LJ computer (PCM) free

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oldditchdoctor

TJ Enthusiast
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Not really sure if this is the right place, if not please relocate. I also couldn't find it in a search.
I have an '04 LJ with the 4.0 and the 42RLE. The tranny is circling the drain, and will die soon. I would love to ditch the computer driven stuff and swap in something that will fit and work well.
I was thinking and older 4.0 and auto trans out of an XJ.
Any ideas?

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You want a transmission that isn’t computer controlled? If so, swap in a 4.0 and a 32RH from a 97-02 TJ. Those transmissions aren’t computer controlled.
 
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Chris said:
You want a transmission that isn’t computer controlled? If so, swap in a 4.0 and a 32RH from a 97-02 TJ. Those transmissions aren’t computer controlled.
Click to expand...
Thanks! I am also noticing that the '04 4.0 has a cover plate for a distributor. Is the gear still in place? Can I dump the computer and go old school? I hate a computer controlled Jeep, too much to break!

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oldditchdoctor said:
Thanks! I am also noticing that the '04 4.0 has a cover plate for a distributor. Is the gear still in place? Can I dump the computer and go old school? I hate a computer controlled Jeep, too much to break!

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Click to expand...

Well if you really don't want a computer, you'd want an old Chevy engine or something with carbs.

I'm not sure what's under that cover, but to convert it from coil packs back to a distributor would be tricky I assume. You'd need to find an engine from an earlier TJ (like a 97 for instance) with the PCM, distributor, etc. Basically in your situation the wise move would be to find a 97, 98, or 99 TJ that is wrecked and buy the entire vehicle for cheap. Swap over the engine (which would be a distributor), PCM, wiring harness, and 32RH transmission. That's about as good as you'll get for a TJ unless you want to swap in some old Chevy engine with carbs!
 
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Your 42rle pcm will get right pissed when it sees its transmission is missing but the aw4 from an xj can be manually controlled with the right shifter. I've seen them swapped into a TJ a few times. Look at the rail shifter (I think it's by rad designs but it's been a few years) otherwise you could do an LS with a carb or a small block chev. I'd honestly keep the tj fuel injection, that pcm is fairly reliable.

—
There must have been a time
when we could have said no.
 
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Drizit said:
I'd honestly keep the tj fuel injection, that pcm is fairly reliable.
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I agree. The PCM on the TJ is actually, very, very simple when compared to the PCM on a much more modern vehicle (say a BMW for instance). Look at a photo of the PCM taken apart and you'll see how simple it is (by how few microchips it has on the board) versus a more modern car.

In addition, carbs are really finicky with altitude and changes of weather. I feel much better wheeling with fuel injection than I would with carbs.
 
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So I broke down and kept the tranny for now. I spent $2300 on Brakes and a tranny rebuild. 220k on the Odometer, new tranny and front brakes... Next 4.56 gears all around.....


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oldditchdoctor said:
So I broke down and kept the tranny for now. I spent $2300 on Brakes and a tranny rebuild. 220k on the Odometer, new tranny and front brakes... Next 4.56 gears all around.....


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Click to expand...
Your trans will thank you for those.

—
There must have been a time
when we could have said no.
 
oldditchdoctor said:
So I broke down and kept the tranny for now. I spent $2300 on Brakes and a tranny rebuild. 220k on the Odometer, new tranny and front brakes... Next 4.56 gears all around.....


Sent from my iPhone using Tapatalk
Click to expand...

Make 100% certain to put a transmission cooler on that. It will last probably twice as long if you do!

The one most of us run and recommend for the 42RLE (including myself) is the DeRale unit:
https://www.amazon.com/gp/product/B004XOO6C2/?tag=wranglerorg-20

Heat is the number one killer of automatic transmissions. Protect that new tranny with a cooler, it will thank you in the long run!
 
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Chris said:
Make 100% certain to put a transmission cooler on that. It will last probably twice as long if you do!

The one most of us run and recommend for the 42RLE (including myself) is the DeRale unit:
https://www.amazon.com/gp/product/B004XOO6C2/?tag=wranglerorg-20

Heat is the number one killer of automatic transmissions. Protect that new tranny with a cooler, it will thank you in the long run!
Click to expand...

I am running a Griffin Radiator and
FlowKooler water pump as of now, should I add the cooler as well?


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