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241/241 doubler?

Stomis

Stomis

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So ive seen it. The guy around the web with the diesel s10 has a pretty damn good writeup about it. The shaft connecting the two cases is basically the front case intermediate shaft machined and tig'd to the rear case input shaft. So Im wondering then if I can use a dodge fixed yoke for the rear case since Ive got to make an adapter plate regardless so the mounting pattern on the second case doesnt matter, neither does the spline count.

Guess this question is just directed towards those very familiar with the insides of a 241. Im trying to explore my options for not using toyota running gear in the s10 since it will save me a bunch of money on adapters and such, but I still want a doubler w/o the 203/205 that weighs as much as a dying star.
 
i wonder if an NP241 can handle the multiplied input torque.
 
muddysub said:
i wonder if an NP241 can handle the multiplied input torque.
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Apparently yes, by far. They seem to be WAY stronger than anyones ever given them credit for. Theres quite a few instances of this setup running around w/o a hitch. Diesel S10 from pirate ran this setup with a welded shaft with 450ftlbs of torque in front of it, then an 800ftlb duramax.
 
I don't see any reason to not use the dodge piece. You use parts from the cases to make the shaft.

You gonna build the shaft. We did an adaptor plate for my buddies 1350/1354 doubler. The guy who did the shaft ( for free) didn't get it straight. He has the D & D machine kit now.

Question though. For this truck do you need a doubler? 700 has a great low first gear combined with the 241 gives a pretty good low range
 
blazinzuk said:
I don't see any reason to not use the dodge piece. You use parts from the cases to make the shaft.

You gonna build the shaft. We did an adaptor plate for my buddies 1350/1354 doubler. The guy who did the shaft ( for free) didn't get it straight. He has the D & D machine kit now.

Question though. For this truck do you need a doubler? 700 has a great low first gear combined with the 241 gives a pretty good low range
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No 700. nv3500, but its still 4:1 first. Since I can do the 241/241 in house for about $20 in material and $125 in tcases Ive decided to go that route. Plus it will be a good project for me to learn to use the lathe :D

I just dont want to do driveshafts etc and then have to redo them. Plus the custom floor for the flatbelly.
 
Too many trucks to keep track of. Yah with a manual trans I would do the doubler. I have heard even when machined for a press fit the shaft is difficult to keep straight. So be careful. The adaptor plate should be easy enough to make though.

Good luck man gonna be cool
 
Sounds neat and will keep my eyes open for updates. My concern would be the low-low range being too low for most practical uses. You are talking 7.4:1 which is a good bit lower than almost every other option out there......huge difference between the 4:1 of a traditional 203/205 doubler and this! A guy in our club bought a 4 speed Atlas with the 10:1 double low and it has been a waste of money. He only uses the 3.8:1 low and high range. At least with the manual transmission you can shift it into 4th or 5th, and of course you can use the single low.
 
Stomis said:
My friend had a stak with 7 something to one. It was a great ratio for crawling.
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I didn't think Stak offered any lower than 5.44:1 ?

I think having a manual trans is the key to making a super low t-case ratio work.
 
6.2Blazer said:
I didn't think Stak offered any lower than 5.44:1 ?

I think having a manual trans is the key to making a super low t-case ratio work.
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Maybe Im mistaken, but it was LOW. And worthless for racing lol.


I picked up the rear case tonight.






Look at the freakin adapter! With a mile long adapter like that its no wonder dodge needed the fixed rear yoke... I also threw the guy $20 and hes gonna cut the output shaft off the trans and mail it to me since the trans is toast anyway :waytogo: Save me a huge pain in the ass. And I guess Im gonna turn this thread into a 241/241 build thread...
 
6.2Blazer said:
Sounds neat and will keep my eyes open for updates. My concern would be the low-low range being too low for most practical uses. You are talking 7.4:1 which is a good bit lower than almost every other option out there......huge difference between the 4:1 of a traditional 203/205 doubler and this! A guy in our club bought a 4 speed Atlas with the 10:1 double low and it has been a waste of money. He only uses the 3.8:1 low and high range. At least with the manual transmission you can shift it into 4th or 5th, and of course you can use the single low.
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don't tell that to the Toyota guys with over 10 to 1 in their doubler set ups.

with a 5 speed it works really well. Double low and using 3rd and 4th alot.

I think it will work very well
 
blazinzuk said:
don't tell that to the Toyota guys with over 10 to 1 in their doubler set ups.

with a 5 speed it works really well. Double low and using 3rd and 4th alot.

I think it will work very well
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Lol never forget, theres always someone more over the top lol.

What about the guys with double sm465s?! holy nuts.
 
blazinzuk said:
don't tell that to the Toyota guys with over 10 to 1 in their doubler set ups.

with a 5 speed it works really well. Double low and using 3rd and 4th alot.

I think it will work very well
Click to expand...

The key factor is total torque output to the tires after all of the multiplication. A stock 22RE 'yota engine has about half the power of a stock TBI 350, which is no power house by any means, so you need twice as much gearing to get the same torque output. Same reason so many Sami off-road rigs have super low t-case gears. They don't do it only for the super duper rock crawling ability but simply because they need that much gearing just for normal trail riding. There are several guys I off-road with that have 'yotas with doublers and most keep the stock 2.2ish:1 low range in both cases. I have seen some with the 4.7:1 is one of the cases but they rarely if ever use double-low.

I'm not saying doublers or extra low range gearing is bad, just that everybody needs to keep it in perspective. For the OP, he makes it clear he has the fab ability to do this fairly cheap and it is a neat project, so I'm all for it. However magazines and sites like Pirate4x4 really talk it up and act like you can't get off the paved roads without a 1,000:1 crawl ratio (along with 40" tires, 1-ton axles with lockers, coilover 4 link suspension, yada, yada, yada).
 
I run a 241/205 doubler with my 700r4 and with 5.38's in the axles to boot. I'm not sure if I'd want much lower than the 5.44:1 my doubler offers. I use it but only to climb technical stuff then I pop it back into 3:1 or more often than not 2:1.
I'm leery of the aluminum housing on the 241 but since it's the first case I was OK with it. I can tell you right now I wouldn't want my rear case as a 241 seeing that much input torque.


blazinzuk said:
I have heard even when machined for a press fit the shaft is difficult to keep straight.
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As a machinist and someone who welds and repairs worn bearing, seal and bushing areas almost daily I can guarantee you it won't stay straight.
I can put .003"+ press on a stub shaft AND weld it in the welding lathe so it's consistent and fast and it'll still bend.

We're not talking eye-ball close kind of stuff here. An intermediate shaft needs to be "perfect".

That being said you can do it, you just need to straighten it afterwards which is what I do and everything is cool.
 
Yep it will never get straight. The runout needs to be dead on for long term survivability in addition to just being reliable.
 
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