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How Bad Is The Ax5? Seriously?


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Hello all.  I was wondering.... is the AX5 really that bad of a transmission, particularly behind a bone-stock 2.5MPFI re-build?  I currently have an AX4 behind my 87's squirrel, and the John- Deere-esque shift throws are kind of endearing.  Reminds me of some old trucks (50's and 60's) that have passed through my family.  While I do have a tendency of overbuilding things, this Comanche has got me thinking that maybe less is more.  I have checked the compression on my mill, and it's an even 120lbs across the board.  I like the fact that it wore evenly, but it is definitely time for a rebuild.  I was thinking of picking up a 2.5 with  Chrysler's MPFI system as I'm much more familiar with that than the Renix stuff I have under the hood, and perhaps even sourcing an AX-15/NP231 set up, but I am beginning to reconsider.  I don"t plan on going past a re-build to stock specs (save for maybe being overbored and having a free flowing exhaust).  Will an AX5 live behind such an engine, or will it grenade when I least expect it?

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The AX5 is not a bad transmission. They are actually pretty tough little transmissions. What you are wanting to do is almost the exact same thing I want to do, MPFI 2.5 and a AX5. The MPFI 2.5 isn't going to be putting out too much more power and torque than a TBI 2.5. You should be just fine. But it all depends on what you want to do, and what all you are going to do with it.

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The AX-5 was used behind the 2.5 up until it was retired in 2002 (at this point it had MPI for 9 years). You'll be fine.

 

Small detail: the 2.5 uses a GM 60* V6 bellhousing pattern, different from the AMC-specific pattern of the 4.0 and AX-15. They won't adapt easily.

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The AX-5 was used behind the 2.5 up until it was retired in 2002 (at this point it had MPI for 9 years). You'll be fine.

 

Small detail: the 2.5 uses a GM 60* V6 bellhousing pattern, different from the AMC-specific pattern of the 4.0 and AX-15. They won't adapt easily.

There's ways around it.  Easiest that I've seen/combobulated in my own head  is using a Dakota AX15 and replacing the tail with a Jeep 4x4 version.  This SHOULD allow use of all factory parts and skip the funky conversions using Camaro 4 banger parts.  As far as what I want out of this build:  I was thinking of having a Jeep that can easily go from semi economical daily driver, to high speed desert runner, and at times be able to be used for extended camping/excursions.  Basically, something that's capable in most conditions (no extreme, King of the Hammers stuff), reliable, and that sips fuel instead of gulping it down like my other 4wd vehicles.  I plan on going no bigger than 31's on the tires (all terrain tires), maintaining a low center of gravity (no/little lift combined with modified body work), efficient use of space for storage, keeping the weight down to reasonable levels, adding a good amount of lighting, and more than likely some kind of traction adding device in the rear end.    

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I got my truck 2.5 years ago. About a month afterward I found a 94XJ 4WD and dragged it home. It wasn't 3-4 days later the clutch slave went out, so the trans swap happened immediately. When I drained the XJ fluid it was milky and full, at some point it had been in water, at that point I really had no choice, I needed to get back on the road.

Point is....For nearly 2.5 the AX5 has whined, synchro from 2nd to 3rd is gone........and she just keeps on......

 

I can't tolerate the whine anymore. About two years ago I found an AX5 out of a Wrangler in Atlanta for $200 so I ran down there and got it, it's been cleaned and sitting on my bench since then. I've since learned that the Wrangler TC is clocked differently, I'll see about plugging the holes and reclocking it. I'll be making this swap in the next couple of weeks.

 

 

Moral of the story- 52K miles later........still rolling.

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you can just use the Dakota 2.5 bell housing for a ax15, but there rare... and put it on a jeep ax15 trans if you want to go that route

I do believe Oreilley's has em available for not TOO much. You just gotta talk the dude in thr green shirt into going into his Keystone (aka "fun) menu.

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The AX5 is a stout transmission and if not abused will last indefinitely behind a 2.5. It will not hold up behind a 350 on the drag strip.

The AX5 is a stout transmission and if not abused will last indefinitely behind a 2.5. It will not hold up behind a 350 on the drag strip.

Nice. Honestly guys, thanks for thr info. I feel better now about swapping one in. It just seems like most jeepers look at the ax5 almost the same as having herpes.

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  • 1 month later...

 

The AX5 is a stout transmission and if not abused will last indefinitely behind a 2.5. It will not hold up behind a 350 on the drag strip.

The AX5 is a stout transmission and if not abused will last indefinitely behind a 2.5. It will not hold up behind a 350 on the drag strip.

Nice. Honestly guys, thanks for thr info. I feel better now about swapping one in. It just seems like most jeepers look at the ax5 almost the same as having herpes.

 

Naw man, ba10 = Herpes.

 

I had a 2.5 and ax4 for a while, and was contemplating swapping in the ax5 if I could find one. What was funny though was when I looked online comparing the two, the 5spd got worse mpg lol! So I got curious and started looking up why. Apparently tbi 2.5 doesn't have enough umph to fill out OD? But perhaps mpfi makes up for that.

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Naw man, ba10 = Herpes.

 

I had a 2.5 and ax4 for a while, and was contemplating swapping in the ax5 if I could find one. What was funny though was when I looked online comparing the two, the 5spd got worse mpg lol! So I got curious and started looking up why. Apparently tbi 2.5 doesn't have enough umph to fill out OD? But perhaps mpfi makes up for that.

 

 

 

As for the analogy...you can get rid of a BA/10

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The AX5 is a stout transmission and if not abused will last indefinitely behind a 2.5. It will not hold up behind a 350 on the drag strip.

The AX5 is a stout transmission and if not abused will last indefinitely behind a 2.5. It will not hold up behind a 350 on the drag strip.

Nice. Honestly guys, thanks for thr info. I feel better now about swapping one in. It just seems like most jeepers look at the ax5 almost the same as having herpes.

 

Naw man, ba10 = Herpes.

 

I had a 2.5 and ax4 for a while, and was contemplating swapping in the ax5 if I could find one. What was funny though was when I looked online comparing the two, the 5spd got worse mpg lol! So I got curious and started looking up why. Apparently tbi 2.5 doesn't have enough umph to fill out OD? But perhaps mpfi makes up for that.

 

 

The AX5 equipped trucks had 4.10 gears, whereas the AX4 equipped ones had 3.55.

 

That makes the final drive ratio in 4th with the AX4 the exact same as in 5th with the AX5. The AX5 got worse mpg because 1st through 4th where geared lower.

 

I run an AX5 with 3.55 gearing in the axles. Around town is the same as it was before, cruising on flat ground 60 mph is the same as before, but cruising 75mph on flat ground I now get 24mpg, where I got 19mpg with the AX4.

 

Mixed mileage in rural Ohio runs about 21-22mpg averaged over two and a half years. I used to average 17 with the 4.0/automatic.

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Yup. That's why IF I swap out the TJ unit, I'll keep the shafts just for the bigger ujoints (and to have spares). I really don't forsee running into issues with a LP unit, what with 31's, a tiny lift and an engine compartment full of angry squirrels. :)

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Ax5 equipped trucks had 4.10 gears, whereas the AX4 equipped ones had 3.55.

 

That makes the final drive ratio in 4th with the AX4 the exact same as in 5th with the AX5. The AX5 got worse mpg because 1st through 4th where geared lower.

 

I run an AX5 with 3.55 gearing in the axles. Around town is the same as it was before, cruising on flat ground 60 mph is the same as before, but cruising 75mph on flat ground I now get 24mpg, where I got 19mpg with the AX4.

 

Mixed mileage in rural Ohio runs about 21-22mpg averaged over two and a half years. I used to average 17 with the 4.0/automatic.

 

Ax5 and 4 cylinder means it *might* have 4.10 gears. I have owned 4 of 7 different XJ's or MJ's with ax5 4 cyl that have had 3.55 and came from factory that way. That puts it at less than 50% of them I have seen or owned coming with 4.10s.

 

 

You could order however you wanted them.

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I am, but only around 3 inches. It SHOULD hold up ok at that height. If not, CAD XJ front ends are a dime a dozen around here. I'll just swap in the TJ guts into one of those housings. Those TJ shafts/ujoints DO look pretty beefy.

 

Only thing swappable are knuckles brakes and shafts. Remember that the d30 had several different wheel bearings with spacing different on the knuckles throughout the years, so calipers, rotors, pads, and bearings are specific to the year of vehicle the axle came from.

 

The gears cannot be swapped between low pinion and high pinion.

 

3" may be ok, but expect to need a custom driveshaft...you will be running the 4 cyl ax5 at full extension

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