Installing a 42RLE in place of a NV3550

Mike_H

Mike_H

autos are better - WRWD508
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Grand Rapids, MI, United States
One of the things about wheeling in Michigan is the varied terrain we have. I can get good rocks and bedrock up north or in private parks. Silver lake sand dunes is about an hour and a half away. Mud is everywhere. I find the low range in my Rubicon t-case is too low for sand and mud.

I had an idea the other day...I could install a 42rle, rubi-crawler, and a 231 T-case. That would get me 2.72 to one and if I engage the rubi-crawler, something like 5.2:1. That would be the best of both worlds, plus I gain the auto for ease of driving.

I have an 04, so it uses a stand alone transmission controller.

I don't mind the manual, but I'm pretty sure it's going to need a rebuild soon anyway...

Am I completely out of my mind?
 
If the auto tranny wiring is in place like it is in the 97-02 TJs I don’t think it would be that bad of a swap. But if you had to add all of the wiring to accommodate I could see that becoming a nightmare.
 
Have you considered a 4 speed transfer case instead? You could do the 2.72/4.30 case and have two different low ratios as well as a stupid deep 11.72 ratio
 
Mike_H said:
One of the things about wheeling in Michigan is the varied terrain we have. I can get good rocks and bedrock up north or in private parks. Silver lake sand dunes is about an hour and a half away. Mud is everywhere. I find the low range in my Rubicon t-case is too low for sand and mud.

I had an idea the other day...I could install a 42rle, rubi-crawler, and a 231 T-case. That would get me 2.72 to one and if I engage the rubi-crawler, something like 5.2:1. That would be the best of both worlds, plus I gain the auto for ease of driving.

I have an 04, so it uses a stand alone transmission controller.

I don't mind the manual, but I'm pretty sure it's going to need a rebuild soon anyway...

Am I completely out of my mind?
Click to expand...
More like 7.4:1 not 5.2:1
 
Steel City 06 said:
Have you considered a 4 speed transfer case instead? You could do the 2.72/4.30 case and have two different low ratios as well as a stupid deep 11.72 ratio
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I'd rather have the flexibility of what you get with the torque converter in an automatic than a 4-speed tcase. Not to mention the added torque from the low-end 2-3x torque multiplication the torque converter provides.
 
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Just don’t use low range for that type of terrain. I’m in Michigan also, I don’t use low range unless I’m in the rocks or something I have to crawl over. Mud sand or anything else keep it in 4h.
 
i was looking for an engine wiring harness and the ones I found automatic or manual were listed for sale as a different part? i found a couple for manual 2006 transmissions but no used ones for an automatic when I looked in a reasonable distance from my local sources last month.
 
Steel City 06 said:
Have you considered a 4 speed transfer case instead? You could do the 2.72/4.30 case and have two different low ratios as well as a stupid deep 11.72 ratio
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Yeah, kinda, but not really. I think the solution posted above will also be much less expressive in the long run, especially considering I can sell the 241 I currently have for a nice chunk of change.
 
Superjay5 said:
Just don’t use low range for that type of terrain. I’m in Michigan also, I don’t use low range unless I’m in the rocks or something I have to crawl over. Mud sand or anything else keep it in 4h.
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I've tried, but my engine doesn't make enough torque to rely on that exclusively.

Do you have an auto or manual?
 
Superjay5 said:
I too have the NV3550. What’s your tire size and gearing?
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I've had issues with both my 33's and my factory 31's. I haven't regeared, so 4:10.

For instance, climbing the dunes at silver lake...I'll run out of power at the top. 4Low is WAY too low there, so I HAVE to run in 4HI...but I need to be running REAL fast at the bottom to get to the top.

Playing in the mud at Rocks and Valleys, that sticky clay will grab if you get stuck. Trying to get moving again in 4HI is a good way to smoke your clutch. 4Low doesn't generate enough wheel speed to clear the tires.
 
Sounds to me like you have more of an issue with the power output of the 4.0 and less of an issue with gearing. For example, in the mud I don’t see the 4.0 being able to push much more wheel speed than you’d get in 4th gear low range, which is equivalent to 1st gear high range since you have the 4:1 case. Maybe it is stroker time ;)
 
Mike_H said:
I've had issues with both my 33's and my factory 31's. I haven't regeared, so 4:10.

For instance, climbing the dunes at silver lake...I'll run out of power at the top. 4Low is WAY too low there, so I HAVE to run in 4HI...but I need to be running REAL fast at the bottom to get to the top.

Playing in the mud at Rocks and Valleys, that sticky clay will grab if you get stuck. Trying to get moving again in 4HI is a good way to smoke your clutch. 4Low doesn't generate enough wheel speed to clear the tires.
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I agree the 4.0 is not the greatest motor to power through mud. I try to avoid it, but being in Michigan I can’t always avoid it. I don’t normally have an issue with it tho’ I just keep my rpms high, actually I just about always keep it at 3,000rpms regardless of my driving, mud I would kick it up even higher. I always try not to clutch in deep mud, I’ve had it pack inbetween the clutch and flywheel before and that was not a good time. Maybe you are keeping your rpms high, but give that a go, the motor can handle it, though anything above 4,000 you have diminishing returns.
 
jodomcfrodo said:
Sounds to me like you have more of an issue with the power output of the 4.0 and less of an issue with gearing. For example, in the mud I don’t see the 4.0 being able to push much more wheel speed than you’d get in 4th gear low range, which is equivalent to 1st gear high range since you have the 4:1 case. Maybe it is stroker time ;)
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Yeah, a stroker would be good...I still think I like the idea of having multiple "low" ranges to switch into though.
 
I have the 4.0 in 2 Rubi's , one nv 3550 5 speed and one the 42 RLE auto... ....I looked into what you are doing seriously....you really are better off to find an auto if that's what you want.

I even talked to Silverstar.

It isn't likely I 'll ever purchase another manual. I understand all the pros and cons but at the end of the day the automatic makes it easier to get the job done. there is some benefit to being able to clean the tires off with the manual
.... But that doesn't negate the better torque and usability of the automatic.
 
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AndyG said:
I have the 4.0 in 2 Rubi's , one nv 3550 5 speed and one the 42 RLE auto... ....I looked into what you are doing seriously....you really are better off to find an auto if that's what you want.

I even talked to Silverstar.

It isn't likely I 'll ever purchase another manual. I understand all the pros and cons but at the end of the day the automatic makes it easier to get the job done. there is some benefit to being able to clean the tires off with the manual
.... But that doesn't negate the better torque and usability of the automatic.
Click to expand...

Who is Silverstar? I know its probably better to purchase an auto to start. I'd just really hate to start over on my build. I have a lot of good parts now, and the chances that I can replicate it for anything near what I have into it are slim to none. Plus, I trust it. I've worked on it and gotten it to the point that I wouldn't hesitate to send my wife cross-country in it, even with 146,000 miles.

The other option is to buy one before selling this, switch parts over, then sell the old one.
 
Mike_H said:
Who is Silverstar? I know its probably better to purchase an auto to start. I'd just really hate to start over on my build. I have a lot of good parts now, and the chances that I can replicate it for anything near what I have into it are slim to none. Plus, I trust it. I've worked on it and gotten it to the point that I wouldn't hesitate to send my wife cross-country in it, even with 146,000 miles.

The other option is to buy one before selling this, switch parts over, then sell the old one.
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Silver Star manufacturers aftermarket transmissions.

I know so much where you are... I spent so much money on my 2003 and when it was all done drove an automatic and was like... WHY ON EARTH DID I BUY A MANUAL.

You're pretty much going to have to have a donor vehicle to make it work... For my money if I was going to figure out how to do it I'd go ahead and find a 3-speed transmission that would work.

I'm not about to say that it can't be done... But so much has changed with vehicle technology it's just not as easy as it was back in the '70s to reconfigure a vehicles powertrain.
 
Mike_H said:
The other option is to buy one before selling this, switch parts over, then sell the old one.
Click to expand...

That's my plan. Not an auto vs manual thing, but a 93.4" vs 103.4" wheelbase thing.

Of course things like rock sliders and fenders are probably not worth the effort of swapping, but basically all of my suspension and drivetrain from transfer case back will be swapped over.
 
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