NP241 vs. NP 271/273 vs. Np203 as a doubler - Pirate4x4.Com : 4x4 and Off-Road Forum
 
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Old 01-04-2013, 11:55 PM   #1 (permalink)
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NP241 vs. NP 271/273 vs. Np203 as a doubler

I know the NP203 is strong but how does it compare in strength and durability to the NP241 and NP271/273 found in Ford Trucks? I have been warned to stay away from the BW1356 planetary gearbox.

Is it better to adapt a heavy gearbox to a heavy transfercase or do I make a smaller lower geared (5:1) gearset to fit in the same transfercase with stronger steel, heat treated and cryogenically treated?
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Old 01-05-2013, 01:21 AM   #2 (permalink)
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I have been warned to stay away from the BW1356 planetary gearbox.

?
Why and by who?

The 1356 doubler is pretty common and regarded as very strong from what I've seen.
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Old 01-05-2013, 01:41 AM   #3 (permalink)
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Actually I was warned to stay away from Behomoth Drivetrain, who sells a 1356 planetary gearset bolt-on unit.

I read a lot of using a NP241 for a doubler, which is used on the Atlas transfercase and wondered how other truck transfercase planetary gearsets compare.
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Old 01-05-2013, 11:25 AM   #4 (permalink)
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What is the use?

The 241 is relatively robust and quiet, doubling and adapting is cheap as you can sometimes get the T-case for free.

Honestly, for a weekend warrior, I don't see a better option for the money.

IIRC, the 271/273 is behind the Power Strokes and Cummins and they hold up well to ridiculous torque and blacktop 4wd launches.
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Old 01-05-2013, 12:19 PM   #5 (permalink)
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Is the NV 271/273 stronger than a NP203 range box? If so then I would be inclined to get my hands on one and adapt the planetary gearset to my NP205.

What is weak and what is strong with regards to gearboxes vs. planetary gearsets.

-cast aluminum is weaker than gray cast iron with the exception of T6 as used in the Atlas transfercase.
-The gears found in NP205s and NP203s are larger than the gears found in a planetary gearset.

I am imagning a planetary gearset made from billet forged steel with gears the same size as found in the NP203.
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Old 01-05-2013, 12:33 PM   #6 (permalink)
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I have been researching dana 20s and NP205s. Neither is the strongest transfercase in the world but both are strong transfercases. I found that the stock dana 20 tends to break the intermediate shaft and the output shaft. According to JB Conversions the NP205 breaks the rear output under extreme conditions. Updates are available. With that said I don't want to buy an adapter. I don't have to.
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Old 01-05-2013, 02:16 PM   #7 (permalink)
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I started a new thread because I do not want my threads to be all over the place.

I am investigating heavier duty planetary gear transfercases.

I really like the idea of a 3:1 NP203 range box bolted to my 1.96:1 NP205 but I wanted to look into hooking a NV/NP271 gearbox

I found a pattern. With 500-ft/lbs of torque at the flywheel and an 80:1 crawl ratio I can idle over rocks with 39-1/2" tires.

With a 454, SM465, LoMax 3:1 NP205, 4.10:1 gears and 39-1/2" tires I would have 81:1 crawl ratio and would crawl over rocks.

With the same situation but with a 1.96:1 NP203 and a 1.96:1 NP205 I would have a lower crawl ratio but the same result

Since I can't get lower gears I realistically need a doubler.

What planetary gearsets from transfercases are comparable in strength to the NP203 range box?

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Old 01-05-2013, 04:31 PM   #8 (permalink)
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I like having 5.88:1, 3:1 and 1.96:1. Less redundancy of gears.

I am leaning toward:
5.11:1 X 3:1 X 1.96:1 X 4.88:1 = 146.63:1
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Old 01-05-2013, 05:12 PM   #9 (permalink)
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What planetary gearsets from transfercases are comparable in strength to the NP203 range box?
I don't know the exact answer to this question but from someone who is also in the market for a doubler this is what I have found.

203 range boxes are great, they are strong and have been in a shit ton of doublers for years without much issue. They are also getting harded and harder to find in the right input spline count(always find the spline count I dont need) and are kinda heavy and only offer 2:1.

The planetary sets from 241's are strong, light weight(in a billet housing) and offer 2.72:1 reduction. The input shafts are very easy to swap and can be had for cheap so that means they work behind tons of different models.

I'm not sure which is actually stronger but the 241 gets my nod simply for being easy/cheap to find.
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Old 01-05-2013, 05:37 PM   #10 (permalink)
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Could you swap the input-gear out on the NP203?

I don't know how the front or transmission side of the NP203 range box differs between Ford GM and Dodge.

The main reason I am not pouncing on the NP203 doubler is that I don't want 2:1 or 1.96:1. I have seen only two low geared NP203s in the last two or three years so they are scarce.

I could get a Ford chain driven transfercase and cut the planetary section away from the rest of the housing. It will bolt right up to my stock adapter and output shaft.
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Old 01-05-2013, 05:52 PM   #11 (permalink)
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I think the input can be swapped between the dodge/chevy but someone smarter than me would have to confirm that.
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Old 01-06-2013, 03:48 PM   #12 (permalink)
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BW1356 planets suck because of the thrust washer issues with them, the range clutch design in the early models and the bronze bushing for the pilot that would need machining to get a needle bearing in there.

Besides the extra strength of the housing, I don't see much advantage of the 271 over the 241. The pilot variances are marginal, since failure is unheard of at that point, and one could make an argument that a double row input bearing is stronger then the larger diameter single row found in the 271, but again it not a point of failure.

I would like to hear more about a 3:1 ratio 203. That is one I have not come across, but the cast iron stuff doesn't come through here often.
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Old 01-06-2013, 04:16 PM   #13 (permalink)
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I'm building a double 205 set up. So far so good and with roc's I'll be the same as a 3.8 atlas with good strength. I guess my point is if you have the time run what fits and what's accessible.




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