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Discussion Starter #1
I am swapping a Cummins into my TJ. I am debating on which method to mate the AX15 to the 4bt. AA has a custom bellhousing that bolts up to the trans and GM flywheel housing. Novak has an adapter that bolts to the trans but then you need a GM bellhousing. BTW my 4bt has a GM bellhousing BP on the flywheel housing. There is only about $100 difference in price so to me that is close enough to just weigh any pros or cons and not worry about the $$.
Any suggestions on which method to mate these two?
 

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Discussion Starter #3
The AX15 will hold up to the 4bt. I know of a couple and they are doing ok. The 4bt had a TH475 behind it.
 

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sorry, no suggestions on best way to mate them but I don't recommend it.

if you plan on using the Jeep for anything other then calm DD duty then it may last for a while, but why would you want a finished swap that has such a weak link? You didn't say what the rest of your rigs specs were or your type of driving or wheeling, I have had a couple of jeeps w/ AX-15s and I know they are tough under extreme conditions, but breakage is not the only thing to worry about, the clutch, syncros, bearings etc. will all go quickly if you run a lot of torque through it

I would try to swap the engine along with matching trans from the donor, or you can get a NV3500 a lot cheaper these days

have you fully considered the extra weight/torque? Will your t-case & axles hold up? dosen't the 4cyl Cummins weigh like 800 lbs? How much torque will it have?
 

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Discussion Starter #5 (Edited)
over's tj I have considered all of the above, this project has been many years in the making. One of the AX15/4bt combos I mentioned gets wheeled a lot, mostly rock crawling and it has destroyed the D44 rear but the AX15/231 has so far held up very well. I don't think the nv3500 is really much stronger than the AX15.
I am running 1 tons, 38" tires, typical midwest wheeling, not rocks like in the southwest. I have run it with the TH475 but want OD for street use. Yes the 4bt weighs about #750, I have 6" springs that have settled down to about 4" with the weight.
Honestly if I break the AX that is not a big deal, I already have a replacement trans, and it is not my DD. I just want to give this trans/t-case a try.
 

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over's tj I have considered all of the above, this project has been many years in the making. One of the AX15/4bt combos I mentioned gets wheeled a lot, mostly rock crawling and it has destroyed the D44 rear but the AX15/231 has so far held up very well.
I am running 1 tons, 38" tires, typical midwest wheeling, not rocks like in the southwest. I have run it with the TH475 but want OD for street use. Yes the 4bt weighs about #750, I have 6" springs that have settled down to about 4" with the weight.
Honestly if I break the AX that is not a big deal, I already have a replacement trans, and it is not my DD. I just want to give this trans/t-case a try.
Hey if you have a back up plan and its no DD, have fun. Just to let you know, I have a feeling my ax15 is about to go south. The syncros are startingt to cry a little more. I am even running the Penzoil syncro mesh stuff$$. They say the limit on these trans are 300hp/300tq. Im sitten around 300hp an 310-330trq to this day.

Have fun.
 

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Discussion Starter #7
Stock power rating for my 4bt is about 110 h/p, 290 ft/lb. Anyway back to the question at hand. Are there any known pros or cons with the two methods of mating these?
 

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Discussion Starter #8 (Edited)
Bringing this back up from the dead for an update. I used the Novak adapter 375-1 and it sucks! Holes didn't match up on the first try. Second try; the same issue because they hand spotted hole locations from my flywheel adapter which I sent to them. Modifications to the plate to increase its strength were agreed to on the phone but were never incorporated into my adapter. Hardware was wrong and in the end I was told to source my own hardware. I was not the only person who got screwed by Novak on this adapter for this engine/trans swap.
The TJ specs as of now are 96 Ford 1 tons, tires range between 37-41. Suspension is a y-link front, double triangulated 4 link rear. The AX-15 is doing great so far, clutch is a 11" big block 68 corvette application, throwout assy is the stock Jeep 4.0. The wheeling I do is typical midwest forest trail wheeling, I don't mud bog, and rock climbing is too far away. Driving style I would say I am a finesse or technical driver not a loud pedal driver unless there is no other option.
Made some mistakes along the way, but live and learn.
 

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I have the nv3550 in my tj and when the 4.0 blows I'm planning on swapping in a cummins. What would be the easiest way for me to adapt my trans to the engine?

I thought the dodge 5.9 cummins used a standard mopar bellhousing, so using that logic couldn't I bolt the bell housing plate for a 5.9 dodge truck onto the 4bt and then bolt my 3550 up? Or is that completely wrong.
 

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Great update.

for the other guy who asked:
Cheapest route possible coming from someone who has done a fair number of these.

buy a 4bt with a NP435, T19 or t18 behind it, they comprise about 85% of the manual tranny equipt 4bts out there. ditch the bell and 4spd. buy yourself a ZF5 speed froma small block equipt 87-97 F250 or F350 usually can be had for $300+/-. it'll bolt up to the engine adapter plate that came with it, gives you a 5.72:1 1st gear and a similar OD. skip the adapter plates. though the dodge option is nice after you buy the plate, bell and the higher priced nv you end up with similar strength and gearing

I know several people who have used AX15's and nv3500's the closer gear shifts are great but the harmonics of the motor are heck on the transmission over time, in a tj your are probably fine for a long time but in FSJ chiefs and larger land cruisers it seems that over time the bearings do get noisy. dont crank the motor up to 200 hp and 500 ft/lbs and expect the tranny to live, in stock hp form and not pushing a ton of weight that ax will live a long life.
 

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What adapter would I need to mate a ZF-5 to my NV241OR? Advance adapters only has a T-19, NP435, or T-18 adapter.
 
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