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Unread 09-05-2011, 01:57 PM   #1
WilliamMc
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350/700r4 swap question? (21 spline)

Okay Iv done a lot of reading and not come up convinced about the 21 vs 23 spine question. I am helping a friend replace his rapidly declining 2.5 ans AX5 with a mostly stock rebuilt 350 and 700r4. The tranny is a 2wd set up and we planed on buying the kit with the adapter and output shaft to put it in frount of the 231 tc. We are going to have the tranny rebuilt anyway as it is high miles. The jeep just has 31 inch tires and see's no real heavy offroading. Although the 23 spline input setup probably would be stronger, Has anyone actually had problems with a 21 spine V8 conversion?? Has anyone done this with the 21 spline and had so far good luck? Is it really that much of a worry?

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Unread 09-05-2011, 03:44 PM   #2
hesserdude07
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why dont you go to anyjunk yard and get a 4x4 700r4? even if its junk you can take the rear housing off it and make your 2wd into a 4wd tranny. And then use a NP231C front case and your NP231J rear housing. Nothing fancy to buy or spend a ton of money...
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Unread 09-05-2011, 04:13 PM   #3
jeepercreeper77
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So if you have a 700r4 out of a 1/2ton 4x4 you can just use a np231c transfer case out of s10?The reason I ask is I will be doing the same swap soon.
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Unread 09-05-2011, 04:36 PM   #4
5.7YJ
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I think the 21 spline shaft would be fine with a mild 350 and 31's.
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Unread 09-06-2011, 03:24 AM   #5
hesserdude07
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Quote:
Originally Posted by jeepercreeper77 View Post
So if you have a 700r4 out of a 1/2ton 4x4 you can just use a np231c transfer case out of s10?The reason I ask is I will be doing the same swap soon.
Makes no difference what the 700r4 comes out of, but yes you can use the 231c out of a s10. My front case is from a 89 S10 blazer, a run a wide chain kit (i dont remember where i bought it, off line somewhere), my rear 231j case, and a JB conversions SYE.
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Unread 09-06-2011, 02:54 PM   #6
WilliamMc
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We already have the 700r4 and we are going to rebuild it anyway so it just seems easest to just get the 21 spline shaft and adapter and thats it, we can bolt up. I just got thru talking to a local old time 4WD shop owner, (Lee), and he also said he would not worry about the 21 spline, he has done many V8, auto conversions with a 21 spline output shaft and he has never had one, (the shaft), break even though he has had a few come back with transfer case failure's and he comented he has people come back that have torn up every transfer case there is. He thinks we will be fine as long as we are aware of the limitations of a 231 in general.
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