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Discussion Starter #1 (Edited)
I am wanting to swap a 4.3 vortec into an 88yj currently running the 2.5/ax15/21spine np231

questions-

1. What year s-10/minivan/ whatever would be best?

2. I want an automatic tranny, will the one behind the vortec be goodfor on-road? If yes, which tranny am i looking for?

2. If the tranny behind the vortec is not the one, then which is?? Preferably, I would like to stay away from adapters

3. Which leads to my next question, will any of these tranny's mate to the 21 spline 231 w/o an adapter? I know i might have to replace the 21 spline input with a 23 spinle one but that is not a problem

This jeep will be my daily driver, on 35's with 4.56 gear's. It will not be my hardcore wheeling rig. My TJ serves that purpose. I am trying to build a very capable everyday/poser jeep to be my primary vehicle. This jeep will see 99% highway and the occasional trip to the mountains on Sunday afternoon. I figure if i am going to have a daily driver it might as well atleast look like a wheeler!!!
 

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well, the auto trans that came with the 4.3 is the TH350. so, yeah, its a good trans. may need a a rebuild from whatever you pull it from. the cool thing is that the 4x4 trucks and mini blazers came with a 4.3, TH350, NP231. so, the T/C may have a different spline count, but you might be able to keep the one from the donor vehicle. bolt it all into your YJ. the speedo is differnt though. if your input spline on your t/case is only 21 splines, it may match the GM t/case. check t make sure. check out http://www.jbconversions.com/, these guys know what you have and what you'll need.
e
p.s. if you havent swapped the trans in your YJ, then you have the ax-5, not the ax-15. the ax-15 only came behind the 6 cyl. engine.
 

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You might look at using a 700R4 or the 4L60E if your using that gearing and plan on alot of highway use. The O.D. would be much more tach friendly. Also I think lo has a better ratio 700R4 = 3.06, 350=2.52
 

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Discussion Starter #4
well, the auto trans that came with the 4.3 is the TH350. so, yeah, its a good trans. may need a a rebuild from whatever you pull it from. the cool thing is that the 4x4 trucks and mini blazers came with a 4.3, TH350, NP231. so, the T/C may have a different spline count, but you might be able to keep the one from the donor vehicle. bolt it all into your YJ. the speedo is differnt though. if your input spline on your t/case is only 21 splines, it may match the GM t/case. check t make sure. check out http://www.jbconversions.com/, these guys know what you have and what you'll need.
e
p.s. if you havent swapped the trans in your YJ, then you have the ax-5, not the ax-15. the ax-15 only came behind the 6 cyl. engine.

Thats cool! I am hoping to avoid adapters like the plague. So will any th-350 bolt up to a 231 or just the ones behind the 4.3? And if it is only behind a 4.3 what year and make of vehicle should i be looking for?
 

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can you narrow your criteria? My 4.3L came stock with a 4L60E behind it and my son's came with a TH350, so there's different tranny's on different years of the motor. If avoiding an adapter is your thing just run the Chevy NP t-case that comes with the drivetrain you pull.
 

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The older 4.3s had TBI and more than likely the TH350.

For power, economy, etc. your going to want the newer vortec 4.3 with multi point fuel injection. This will also have a 4l60-e with. This motor combo will be the best bet for all the reason mentioned above.
 

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Yep, go with the multi-port 4.3 and the Al460E. That's what I got and I do a lot of on-hwy driving. With 35" tires and 4.56 gears in the axles I run about 2,500 RPM at 65 MPH. The combo is also great for the off-hwy driving I do as well.

As far as the T-case goes, you should be able to upgrade the internals of the 231 to a 23 spline input. Can't help you much on that though cause I replaced mine with an Atlas.
 

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Discussion Starter #8
Yep, go with the multi-port 4.3 and the Al460E. That's what I got and I do a lot of on-hwy driving. With 35" tires and 4.56 gears in the axles I run about 2,500 RPM at 65 MPH. The combo is also great for the off-hwy driving I do as well.

As far as the T-case goes, you should be able to upgrade the internals of the 231 to a 23 spline input. Can't help you much on that though cause I replaced mine with an Atlas.

Okay, but again what vehicle and what year had the mulit-port 4.3 and the
Al4603?
 

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Yep, go with the multi-port 4.3 and the Al460E. That's what I got and I do a lot of on-hwy driving. With 35" tires and 4.56 gears in the axles I run about 2,500 RPM at 65 MPH. The combo is also great for the off-hwy driving I do as well.

As far as the T-case goes, you should be able to upgrade the internals of the 231 to a 23 spline input. Can't help you much on that though cause I replaced mine with an Atlas.
How are you pulling that kind of RPM's? I've got the same set up and run just shy of 2000 RPM's at that speed. 4.3L "w" motor, 4L60E, 35" toyo's, and 4.56 gears

oh, and for the original poster. 96 and up Blazer, S10, and Astro van are what you want to look for.
 

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Discussion Starter #10
How are you pulling that kind of RPM's? I've got the same set up and run just shy of 2000 RPM's at that speed. 4.3L "w" motor, 4L60E, 35" toyo's, and 4.56 gears

oh, and for the original poster. 96 and up Blazer, S10, and Astro van are what you want to look for.

Thanks!! Is the astro van a rear wheel drive van??? If it is front wheel drive i don't see how that would work???
 

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well, the auto trans that came with the 4.3 is the TH350. so, yeah, its a good trans. may need a a rebuild from whatever you pull it from. the cool thing is that the 4x4 trucks and mini blazers came with a 4.3, TH350, NP231. so, the T/C may have a different spline count, but you might be able to keep the one from the donor vehicle. bolt it all into your YJ. the speedo is differnt though. if your input spline on your t/case is only 21 splines, it may match the GM t/case. check t make sure. check out http://www.jbconversions.com/, these guys know what you have and what you'll need.
e
p.s. if you havent swapped the trans in your YJ, then you have the ax-5, not the ax-15. the ax-15 only came behind the 6 cyl. engine.

Ok, so basically, the first tranny that came with the 4.3 tbi motor was a 700r4, then with the vortech which started in 93 had the 4l60e, and it was better, about the best 4.3 to go with if you're into the vortech is the 95, it had the most power/torque. the 96 came out with the vortech which they still have, and they cut way down on the runners on the heads, and lost a lot of power. Besides, if you want the cool lookin cpi intake then you need between a 93, and 95. Personally, I would go with the 92, which is still tbi, because the cpi has a funky injector setup, and its really spendy to fix WHEN it breaks. besides, you can find a set of 93, to 95 vortech heads, and bolt them on with an edelbrock manifold, and you're golden, you get the best of both worlds. And the tranny is easier to deal with cause its not electronically controlled. But its up to you,
 

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How are you pulling that kind of RPM's? I've got the same set up and run just shy of 2000 RPM's at that speed. 4.3L "w" motor, 4L60E, 35" toyo's, and 4.56 gears

oh, and for the original poster. 96 and up Blazer, S10, and Astro van are what you want to look for.
My speedo is a little off, so I'm kind of guessing. That's why I said "about". 2500 RPMs could be more like 70 MPH.
 

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Thanks!! Is the astro van a rear wheel drive van??? If it is front wheel drive i don't see how that would work???
Astro van is rear wheel drive. I have one and it has the same engine as my jeep.:D
 

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oh yeah, and the 4.3 came with either a 207, or the 241. The biggest difference you need to look for as far as mounting your 231 to a chevy auto is the spline count, another thing to look for is whether or not your case is set up for the recessed output shaft on the tranny, or flush. Look on advanceadapters.com they have oogles of info on this stuff, Brent
 
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