NP435 to a AX15 manual. What do I need to do / worth it?

[70Canada]

Really wanting to understand what it'd take to get out from under my current set up of the 302/NP435/dana 20 and into a AX15. Have the 1" body lift.
it had the 435 in it when i bought it 13 yrs ago. purpose is 80/20 street , light trail and was looking for something installation friendly as well as close fit. don't quite know what will happened with the shifter though.. any and all with experience .. its welcome.. !

 

[70Canada]

should add, that my intent would be to run a 33" tire with the option to move up to a 35 when i chose to do so (upgrade gearing in front and rear axles to suit 4.56 or 4.88 but unsure of right harmony with the AX15 with other components and setups close to mine.

 

[70Canada]

sorry, currently axle gearing is 3.50/3.54 Dana 30 front and the dana 30 is what i'm going to stick with. see no reason to change at this point until possibly rolling into 35's / SL but until my money tree springs a few more branches... it is what it is.

 

[blubuckaroo]

Your gear ratio really depends on what sort of "street driving" you'll be doing.

Even if you decide to keep the 435, your 3.50 gears are sort of high for 33" tires. It's pretty tough on the clutch. Swap it out to an overdrive like the AX-15 and high gear is pretty much worthless.

So, here's the rabbit hole. Tranny and gearing. Pretty expensive all at once if you ask me.

Here's an option...
Lower the gearing but don't go crazy. 4.11s are pretty popular for that setup. You'll probably like it for the street.
Freeway driving might be another story. But how much freeway do you plan for this vehicle?

That 435 is an excellent choice for light trails. Better than an AX-15.
Don't be too hasty!

As far as the mod goes, the AX-15 is very similar to the NV3550 I put in a few years ago to replace my C4 auto. It was one of the easiest mods I've done. Yours would be even easier since you already have the bell housing and clutch pedal & linkage.

 

[Redneck72Bronco]

I recently put an AX15 in my Bronco. Extremely easy installation. I went with a used transmission from an old Jeep and then got the conversion kit from Wild Horses 4x4 along with the twin stick conversion. I'm running 35's with 4.11 gears. I haven't fired it up to run it yet (still running the wiring) but I've heard that is a great street set-up. If I ever want to go to larger tires, I will need to re-gear to 4.56+ though.

 

[blubuckaroo]

I recently put an AX15 in my Bronco. Extremely easy installation. I went with a used transmission from an old Jeep and then got the conversion kit from Wild Horses 4x4 along with the twin stick conversion. I'm running 35's with 4.11 gears. I haven't fired it up to run it yet (still running the wiring) but I've heard that is a great street set-up. If I ever want to go to larger tires, I will need to re-gear to 4.56+ though.

My setup is very similar to yours. My tranny is the NV3550. The Bronco has 4.11 gears and 33" tires. The difference between the AX-15 and NV3550 is mainly the first gear ratio. The AX-15 has 3.83, and the NV3550 has a lower 4.01.
This setup has worked well for me, since I drive a lot of interstate highway. I routinely cruise in the 70-75 range for long periods.
I even use the overdrive when I pull the camp trailer. I do shift down on the steeper grades though.
The low first gear comes in handy too, when stuck in slow stop and go commuter time traffic. I just leave it in first and idle along. You wouldn't be able to do that with a three speed, and its 2.99 first gear.

 

[70Canada]

thank you guys for the feedback! very much appreciated. work gets in the way i definitely don't want to be hast to unload the 435. and maybe you're right. until the rest of the rig catches up to the intended tranny. then what I have may be fit for purpose right now.

 

[Nothing Special]

I've driven a pickup with an NP435, I used to have the stock 3 speed manual in my Bronco and it has an NV-3550 now. The Bronco has 4.10s and 33" tires with a stockish 302.

The 5 speed is nice, but I wouldn't say that it completely changed the driving experience. Having a lower 1st gear is great for starting with the marginal 4.10 / 33" combo (which personally I actually love). Definitely a little less clutch slipping to start, especially if on hill or towing my boat. And the overdrive is great on the highway, and even to drive around town (I can hit overdrive at about 30 - 35 mph if I'm done accelerating, it's really quiet and can hold speed fine).

Having driven an NP435, the smoother shifting NV-3550 is definitely nice.

Adapting my 3550 to my engine wasn't too bad, I'd guess the AX15 would be similar. I put an Atlas on the back of my trans, so I can't speak to adapting it to a model 20.

Is it worth doing? I'm glad I did it, but honestly I appreciate the Atlas I added at the same time a lot more, and the wider range of gearing I have helps span the gap between the 1:1 high and 4.3:1 low in the transfer case. In your case I think you'd like it, but you might prefer to spend your money on other things. And take that for what it's worth

 

[70Canada]

Thanks Nothing special! I'm thinking that for my driving around town that i'll kick up to my 17x9 with the 35s right now, set my expectations low. no big wheeling so not worried about breaking anything. but clutch slip, yes. if my 4.56 gearing doesn't catch up soon though.. may be a clutch in my future... especially with my son just turning 14 LOL. and most of all.. a little bit of a tired original 302 that could use an awakening. so crazier thoughts of pushing to a 302 juiced up to 250-275 hp. I can work through a build on my engine over the winter .. but i def need a garage heater!!! anyone selling one lol?

 

[70Canada]

at the end of the day.. a rig that'll ride at 65mph is fine by me. I don't need to rip down the highway at a higher speed than that. the current set up is power sucking at stock 3.50/np435, stock 302 with 600 holley/performer intake. any grade and she'll start to suck wind and can't keep into it with the current 31s. but like i say and everyone else... a work in progress, I am not wanting to take a cut/paste approach but also can't argue with tried and proven either so thanks again for the feedback

 

[tabyers]

I had a 435 w/3.50 and 31s and 33s, now I have an AX w/4.11 and 31s and I can’t wait to swap to 4.56. I’m no speed demon in the bronc though

Anyhow, food for thought here, I’d take the AX even if it didn’t have a OD. That split between 2nd and 3rd on the 435 is murder, street or trail. Just my take on em.

 

[70Canada]

hah.. agreed. i think the 2nd to 3rd is bearable but 3 to 4 just kills all the fun . I still like the idea of the AX15. 5 speed. you say you're going to 4.56 but running 31s but my intent is that the AX 5 speed swap / 4.56 and the 35s with some fresh hp/torque will be just what my rig needs .. maybe a little optimistic but i always have to remember that I'm not busting stuff on the trail blazing it up.. its a street machine that we take fishing once or twice a summer

 

[70Canada]

i think with the 35 rotation that the 4.56's will hit the 100km/hr (60mph) that i need anyways. but again,, i'm still working through all the numbers and such and talking to the subject matter experts

 

[rguest3]

I have the 435 in a 71 F-100 and HATE it. I am eager to change out to another trans any chance I get.

I have a Bronco with a 351W/AX-15 now in the shop and it is so much more enjoyable to drive. 3.50 gear and 31s now. I'm going to swap to 4.56 gears and a 285/70/17 tire. I also swapped the shifter to the B&M and this made a very nice improvement as well with a shorter throw to change gears.

 

[70Canada]

great note rguest3... i like the comment about the shifter accommodating a nicer shift. thanks

 

[Tiko433]

I’m running a 4.56 with my AX15 / D-20 and 33s. I like the combo . As fast as you want to go in 5th. 1st is street friendly. Also the B&M shifter

 

[Pa PITT]

I'M THE OLD FART AGAIN... I've driven my 1980 Bronco w/ NP435 & 3:55's with30x9:50 R15's.. I must have put close to 200,000 miles on it.
Then I got my 1972 Bronco w/302 & swapped it from 3 speed to NP435 TWIN Sticks on my Dana 20. & It too has 3:55's... with 265../ 70/ R16's..
I've always thought it was the best swap I've done to my 72 Bronco .. P/S DISK ..
bUT THEN I SWAPPED MY 302 OUT FOR THE 4bt Cummins .. sweet. & I left the NP435 IN PLACE. I really wanted an O/D& I gathered up the dodge diesel 5 speed NV4500 I THINK IT WAS. bUT I Kept sizing up the cost & I finally sold my4500 & stuff.
I'm in love with 1st gear in the NP435.. Mine is 4:54 I THINK..
I've never noticed that big split in either of myBronco's 435's.
But I woke up old one morning & DECIDED SWAPPING to the NV4500 was just too much work for me to do. along with at least another $1500.00 for more swap parts .
... & I had, bell, flywheel, clutch, trans, yoke,. But I still needed the shifter. drive shaft work for most likely 2 drive shafts . Modification on the floor board . New U-joints ..& What if the rear shaft has a bad angle i NEEDED TO WORK OUT . & mAYBE AN OVERHAUL INSIDE THE 5 SPEED IF My used trans wasn't as good a I hoped it is.
..... SO I SOLD MINE STUFF & LOVE MY np435.