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207/207 doubler t-case


Joop
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Been fooling around with the idea of making a doubler t-case for my diesel out of a spare 207 i have. I have pulled it apart and taken some measurements, and so far i can't see why it won't work. New splines have to be machined on the output shaft of the front case, and an adaptor plate has to be made, but I know people who do that for a living. Anyone done something similar? Just looking for ideas and inspiration here..

 

I know there are better options out there, but one of my goals with this build is to see how much fun I can get out of the parts I already have laying around. (read: I'm broke :grrrr: ...)

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It can be done. All you need is the $$$. Or the knowledge and equipment to do it yourself. I once double teamed two T20's by uniting the output-input shafts with a U Joint. Just looking i think it could also be done with the 270 and 231 series. The alignment has to be perfect if you expect to get any life out of it. If you have the room the simplest, and cheapest method would be to use a short driveshaft between them. I have also offset them and connected them with a roller chain, substituting chain gears for the UJoints.

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  • 2 months later...

Apparently the output shaft is made of some kind of hardened steel and can't be machined down and re-splined to match the input shaft. Did some more research about the subject and it turned out S10's from early 80s with 2.8 and auto used a 27spline input np207. So i found an input shaft for 10$ on ebay. (Even with shipping being 30$ its a steal compared to bying a complete transfer at the junkyard, they go for over 600$ over here..) Installed that input shaft in the rear transfer and startet building an adaptor from whatever junk I found at work.

Here are the two transfers side by side, s10 shaft between them. The blue plate on the left case is a industrial pipe-flange with 3 holes drilled in it and boltet to the case, the steel-ring at the bottom is a 205 clock-ring i got from a friend.

 

 

 

 

 

 

 

All thats left is to get the surfaces machined dowm, they warped a little bit during welding, and to cut off the front output of the first case and make a plate to block of the big hole.

 

I really should write more about what i did, but my internet browser is in a crappy mood today :hateputers: anyway I tried to copy this setup http://www.naxja.org/forum/showthread.php?t=68223

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Can someone explain the benefit of running two transfer cases? :???:

 

Generally when one runs a doubler, the front case is just the reduction unit section, and the offshoot part of the case for the front output is hacked off. The back case is a standard T-case.

 

What this gives you is the option for a very low crawl ratio.

 

Lets say you have an AX-15, with a 231, and 4.10 geared axles.

 

Your crawl ratio is determined by your transmission's lowest gear ratio, multiplied by the transfer case's low range ratio, times the axle ratio.

 

So the above combo would have a crawl ratio of 3.83(AX-15's first gear) x 2.72(NP 231's low range) x 4.10(axle) = 42.71:1

 

Adding the second T-case reduction unit gives you the option of reducing that to 116.78:1

 

In case you don't know what the crawl ratio is, it means that the motor will have to spin x number of times for the wheels to turn once. Taking that from 42.71 to 116.78 makes it much easier on the motor, and better for certain offroad conditions.

 

It also gives you an easy choice for 2wd LOW, by just activating the front case's reduction unit.

 

If you picked two t-cases with different low range ratios, it also gives you 3 low range choices instead of 2.

 

What the OP had done, however, is usually not how it's done. He's basically just bolted them together, which makes it way too long, puts a great deal of extra stress on the cast aluminum casings, and it would appear he's made it impossible to bolt up a front driveshaft.

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What the OP had done, however, is usually not how it's done. He's basically just bolted them together, which makes it way too long, puts a great deal of extra stress on the cast aluminum casings, and it would appear he's made it impossible to bolt up a front driveshaft.

 

LMAO!!!!

EPIC WIN OF FAIL, genovast, you made my night

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What the OP had done, however, is usually not how it's done. He's basically just bolted them together, which makes it way too long, puts a great deal of extra stress on the cast aluminum casings, and it would appear he's made it impossible to bolt up a front driveshaft.

 

LMAO!!!!

EPIC WIN OF FAIL, genovast, you made my night

 

if you noticed, there's no front input in the front tcase, and he already chopped the front housing down.

 

so, he's just not done with it..

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What the OP had done, however, is usually not how it's done. He's basically just bolted them together, which makes it way too long, puts a great deal of extra stress on the cast aluminum casings, and it would appear he's made it impossible to bolt up a front driveshaft.

 

LMAO!!!!

EPIC WIN OF FAIL, genovast, you made my night

 

if you noticed, there's no front input in the front tcase, and he already chopped the front housing down.

 

so, he's just not done with it..

 

i know that :yes:

I'm just laughing at genovast's input :popcorn: jamminz.gif

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I know this is a poor setup, and its not what i first wanted. But its all i got at the moment. Id rather blow up the diesel and 2 np207's in the woods and have a good story for later, than to sit at home wathing tv because I don't have anything to wheel. Either way, I'm saving up money for a better drivetrain. It just won't happend this year and probably not the next.

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Theres alot to be said for working with what you have. It may not be pretty, or the best stuff in the world, but if its what you have and can make it work, more power to you. I too have to put an NP207 in my 87 for the 4x4 conversion.... because its what I have. What I don't have is any kind of budget to get something better. Unless something better falls in my lap, then I have no choice. Thing I do have are tools, and time, and injenuity (sp?). I'm sure JOOP is the same way. What can we do? MAKE IT WORK! I'm not getting pissy here, just saying we do what we have to do. If I had the money for better stuff, you know damned sure Id have it! But until that time comes..... :dunno: :cheers:

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