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Need some help/info fast. thanks :) 91 MJ


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I am about to pick up a super super nice 91 MJ. it has a new 4.0L HO crate engine, zero rust and TJ buckets ect. Here is the kicker! its 2wd. I feel like its worth it, but want to be sure. It has a 2wd ax-15 and 35 rear. What do I need to do to make it a stock type 4x4???? i know I will need the obvious parts, 231, 30 front, drive shafts, and new cross member. Anything else? I mainly want to find out if it is possible to remove the 2wd tail shaft from the ax-15 and bolt the t-case up w/ no mods? Is this possible, or will I need a whole new tranny?

thanks for any light you can shed! -J

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so what is involved? More than just removing the tailshaft and bolting up the t-case?

all the decent 23spline 4wd ax-15's around here are more than 600 bucks...I can't afford that! I hope I didnt make a mistake buying this thing. I thought it would be no big deal.

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You've basically got the idea, however, here's a quick list of what you'll need.

 

D30 with gears matching your rear axle- most likely 3.07. Now would be a good time to hunt for some better gearing though.

 

You'll need a 4wd AX-15. You can't just remove the tailshaft for a 4wd one, the output shafts themselves are different.

 

Transfercase.. either a 231 or 242(if you want the full time 4wd/AWD)

 

Shifter linkages and handle to go with the transfer case.

 

Front driveshaft. Best to get it from a 4.0/5 speed, as the lengths vary with which motor and transmission it has.

 

Shorter rear driveshaft. Your best bet is probably having your 2wd one cut down, as it's not the easiest to find a 4wd shaft.

 

All the front suspension components are the same between 2wd and 4wd(coils/shocks/control arms/trackbar/steering/sway bar. You will need to use the 4wd brakes and calipers for the D30, however. Most year D30s will bolt right on no problems, but there are several generations of brakes.

 

When you hunt down the 4wd AX-15, I strongly recommend trying to get one with an external slave setup. It'll be a little bit more time to convert from internal to external, but it will save you headaches down the road if you ever have problems with the clutch hydraulics.

 

I don't think I forgot anything, it's basically a bolt-on procedure. The hole for the 4wd shifter is already there, just with a plate over it.

 

Oh, and you won't need a new crossmember. They're all identical.

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Thats bad news, I know I can't afford a new tranny right now... on top of every thing else. My plan is to find some xj axles hopefully non-vac disconnect. I have heard that there is something about the TJ ax15 that is different and may not work, is this true? Aren't they the ones that have external slaves? or did some yj's have it too?

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Where are you located? I've got a matching F+R 4wd axles for free if you can do a little cleanup work yourself.

 

In any case, for a clean body, even if it doesn't have all the parts you wanted it's always worth it. Far better to start with a clean body and swap a bunch of parts to end up with the truck you want, rather than a truck with the parts you want that needs a lot of body work... Clean '91s are hard to come by so if you've got one you're already ahead of the game :cheers:

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External slaves aren't a matter of what vehicle-but what year. The internal slave was used from 87-mid93ish. Any AX-15 after 94 should be external. Let me emphasis should, as if I don't you'll go out and find a stock 95 with an internal.

 

As far as the TJ trans, it'll work. YJs and TJs are essentially the same transmission, but the transfercase is clocked a couple degrees up more than the XJ/MJ ones, so there's a possibility of the T-case hitting the floor. It's not really a big deal, if it looks like it's gonna hit you can always give it a little more room with a little love from a hammer.

 

Keep looking around for an AX-15. I wouldn't bother with ebay or anything, keep an eye out on CL, and post up a WTB thread in the classifieds here on CC. There's probably a good chance someone's in your area that can help you out with getting one. The last one I paid for was an external, came with a 231, and I paid 200.

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Where are you located? I've got a matching F+R 4wd axles for free if you can do a little cleanup work yourself.

 

In any case, for a clean body, even if it doesn't have all the parts you wanted it's always worth it. Far better to start with a clean body and swap a bunch of parts to end up with the truck you want, rather than a truck with the parts you want that needs a lot of body work... Clean '91s are hard to come by so if you've got one you're already ahead of the game :cheers:

 

I'm in North Carolina...Is the front non-vac disconnect? I mean I won't look a gift horse in the mouth, but Its quite a ride to RI. Thanks man!

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External slaves aren't a matter of what vehicle-but what year. The internal slave was used from 87-mid93ish. Any AX-15 after 94 should be external. Let me emphasis should, as if I don't you'll go out and find a stock 95 with an internal.

 

As far as the TJ trans, it'll work. YJs and TJs are essentially the same transmission, but the transfercase is clocked a couple degrees up more than the XJ/MJ ones, so there's a possibility of the T-case hitting the floor. It's not really a big deal, if it looks like it's gonna hit you can always give it a little more room with a little love from a hammer.

 

Keep looking around for an AX-15. I wouldn't bother with ebay or anything, keep an eye out on CL, and post up a WTB thread in the classifieds here on CC. There's probably a good chance someone's in your area that can help you out with getting one. The last one I paid for was an external, came with a 231, and I paid 200.

 

the only reason I mention the wranglers is b/c I feel like it will be tough to find am xj/mj trans/t-case...of coarse I could just get the trans from the wrangler and case from an xj...will all 23spln 231's work?

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Being the resident PITA pedant, let me jump in and point out that there MAY be some lack of clarity regarding terminology here.

 

To convert a 2WD tranny to 4WD, you would remove and replace the tailshaft. But ... note that I said tail shaft. Otherwise known as output shaft. We're not talking about just the long, tapered tailshaft housing, which is perhaps what you had in mind. The 2WD tranny has a long tailshaft and tailshaft housing, that ends in a spline that mates up with the front yoke of the driveshaft. The 4WD tranny has a comparatively short tailshaft that ends in a spline count that mates up with the input of the transfer case. The 4WD tranny, of course, does not have a tailshaft housing.

 

So ... to convert the 2WD tranny, you have to remove and discard both the tailshaft housing and the tailshaft. You have to find a 4WD output shaft (of the correct length and spline count to mate with whatever transfer case you have) and install that, THEN you can think about bolting up the transfer case.

 

By the time you buy the necessary parts, it's probably cheaper to buy a 4WD transmission.

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Being the resident PITA pedant, let me jump in and point out that there MAY be some lack of clarity regarding terminology here.

 

To convert a 2WD tranny to 4WD, you would remove and replace the tailshaft. But ... note that I said tail shaft. Otherwise known as output shaft. We're not talking about just the long, tapered tailshaft housing, which is perhaps what you had in mind. The 2WD tranny has a long tailshaft and tailshaft housing, that ends in a spline that mates up with the front yoke of the driveshaft. The 4WD tranny has a comparatively short tailshaft that ends in a spline count that mates up with the input of the transfer case. The 4WD tranny, of course, does not have a tailshaft housing.

 

So ... to convert the 2WD tranny, you have to remove and discard both the tailshaft housing and the tailshaft. You have to find a 4WD output shaft (of the correct length and spline count to mate with whatever transfer case you have) and install that, THEN you can think about bolting up the transfer case.

 

By the time you buy the necessary parts, it's probably cheaper to buy a 4WD transmission.

 

AHH, I see. gotcha. bummer...

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the only reason I mention the wranglers is b/c I feel like it will be tough to find am xj/mj trans/t-case...of coarse I could just get the trans from the wrangler and case from an xj...will all 23spln 231's work?

It should not be difficult to find XJs. Why get involved in mixing and matching? Buy a transmission and transfer case together and you know they work together. XJs are all over the place. The u-pull I used to go to had rows of them.

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the only reason I mention the wranglers is b/c I feel like it will be tough to find am xj/mj trans/t-case...of coarse I could just get the trans from the wrangler and case from an xj...will all 23spln 231's work?

It should not be difficult to find XJs. Why get involved in mixing and matching? Buy a transmission and transfer case together and you know they work together. XJs are all over the place. The u-pull I used to go to had rows of them.

 

plenty of xj's just not ones w/ ax15's

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You can update it in stages too. A 4wd front axle will bolt right in without any change to the trans. The 4wd trans and t-case will bolt in without the front axle. Heck, any MJ lift kit will bolt right in to a 2wd MJ. Personally, I would upgrade the rear axle ratio first. :thumbsup:

Also, try car-part.com if you haven't yet.

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^ yeah thats something I condsidered...Maybe doing the lift and axles first and saving the trans/tcase for last... will 3" clear 33's? I really am only looking to build a DD/mild wheeler/camping rig. don't want to go too big this time. My toyota I just sodl was fully built on 37's and I am tired of driving a rig that heavily modded.

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Not really. You have a couple options with the CAD.

 

1. Leave it stock and hope it functions.

2. Pop the actuator off, and lock the shift fork over so it's always engaged.

3. Get the proper seal and install a later model one piece shaft.

4. Get a manual locking kit, either vacuum or cable, to give you the option to control if it's engaged or not. Really the only advantage to doing this, is it gives you a 2wd low range option.

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Find a set of 4.10 axles regardless of the tire size. :D

 

I disagree. I've driven Pat's 87 on 4.10s with IIRC 31s, and for street driving it felt like too much gear. I think 3.73 would have been nicer.

 

 

It's probably more gear than you're used to, but it's not too much. youd get used to the difference. :thumbsup: Heck, it's not enough gear if the engine is a 2.5L.

 

Plus, 4.10s are way easier to find than 3.73s in a high-pinion Dana 30. :yes:

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