Question for the NP435 experts

Hi. I believe this is my first post in the forum. I've been reading and researching for a while, but no posting. Any way, I have a '71 with a 3" lift and 33" tires. The rest is pretty much stock. I suspect that my axle ratios are a 3.50, or there abouts. The truck does great on the freeway with the 33's. My problem is in 1st gear it just doesn't seem to have enough pull and I'm not really talking about off-roading. I've been thinking about getting an NP435 for some time in order to get the lower 1st gear. So, I've been doing a lot of reading and looking. I came across a tranny that I was told came out of a 2WD Ford truck, so I bought it for a decent price. The interesting thing is that the rear output has a park brake attached to it. I've not seen any reference to a brake on the output until last night where I came across an internet article on an NP435 that was used on a Ford F600. The article mentions the park brake as well as the fact that the input shaft on these trannys is slightly larger than the normal NP435s. I'm trying to find out if this is really true or, is it possible that other NP435s with the "normal" input shaft came with the park brake on the rear. Is it possible to change out the input shaft for one that is the correct size for our Broncos? I appreciate the help. This is my first Bronco and I've only had it about 4 months. Thanks.

The NP435 isn't really going to help. You start out in 2nd with NP435's. 1st and 2nd are too far apart for regular shifts.

You can swap out the input shafts, not sure it would be practical though. I've never seen one with a parking brake, but it wouldn't surprise me. The main thing that matters is the 28 spline output. Some need to be cut to fit, neither of mine needed to be cut.

One thing to watch out for is the top cover height. Some are quite a bit taller which can create clearance issues with the dash. The taller covers do have a shorter shift throw though.

Personally, I'd look for a 2wd model bolted to a 302/351w so it will bolt right up! The 4wd models bolted to a dana 21 should also work.

I'm with Nobody in saying that it's not gonna help you in the way you're intending for everyday street driving. Might look at adressing your motor a little if you feel that down on the power. The 435 essentially buys you a great crawling gear for offroad but it's too low for starting out at stop signs and stop lights. Like stated above, we use 2-4 for everday town type drivin'. Some pics or your tranny would help narrow down what you've actually picked up. If you've got some oddball version that requires swapping input and output shafts I'd recommend just sourcing the right 2wd version for a near bolt in solution. You can find them behind all kinds of engines. I've got 2 that were behind 360s and one that was behind a 351M. They'll bolt right up to your stock 302 bellhousing...

My rig right now runs stock 3.50 gears, 33" tires and a 435 and it's great with a fresh 302 under the hood. If I was keeping the 33s, I'd stick with the gearing in my rig but I'm swapping them out for 4.10s in anticipation of the next tire purchase being 35s.

Nothing wrong with starting out in low. You will just be going to 2nd really quick. Thought about a ZF?

Guys, thanks for the info. I was planning on using the 435 in 2nd, 3rd, and 4th only on the highway. The gear ratios for 2-4 seem to be pretty close the the stock 3-sp 1-3 gears. I only want to use 1st gear when I need to "climb" something. That was my thought, any way. I haven't pulled off the brake yet, so I don't know how many splines are on the output. So, if the input is wrong and the output is wrong, I'll probably end up scrapping the whole thing, but I was hoping the output brake came on more models than the F600 Ford. I can go out and measure the input shaft, then I'll know. Oh, forgot to mention that the top isn't tapped for the back-up light switch. I suppose I could drill and tap it myself. I'm learning more every day.

I don't know much about the ZF. I read that the NP435 was pretty close to a bolt-in replacement, assuming you get the right one, I suppose. Haven't researched the ZF. Seems like I remember reading they are more expensive than the 435s to get.

I'm no expert on NP435s, but have also been looking for one. I saw one in the JY on an F600 with the parking brake on the rear, & another one that recently sold on ebay (I actually went back with help to pull the JY one, but the whole thing was gone. It was a cool truck, I'm glad someone saved it). I wondered if the output shaft would work. I've seen output shafts for sale (Like this one at Tom's) to convert a married 4wd NP435 to use with a D20, & thought if the brake version was wrong that one of those might take care of it.

As for the input shaft, Novac's site gives ID info & pics on NP435s. This is from their Ford section:

The Ford NP435 has a 1-1/16" diameter, ten spline input shaft that has a stick-out of 6-1/2" from the front face of the transmission. The pilot tip of the transmission measures ~17mm. The front bearing retainer flange measures 4.85" and the bearing retainer tube is 1.43" in diameter. The front bolt pattern is the symmetrical Ford "butterfly" pattern; roughly 8-1/2" wide by 6-5/16" tall. The input shaft stick-out length is 6-1/2".

Click to expand...

I would think that you could measure your trans & compare. If the length of the input shaft matches, but the diameter is different, it might be possible to find a clutch disc & pilot bushing that would still allow it to work.

I ended up getting an NP435 that had been run in a Bronco. It isn't installed yet. I can get some measurements off of it if you need something. Also, if you're interested in selling the parking brake stuff, let me know.

Cant really tell you for sure about a 435 out of a F600 Most likely it does have a larger input and output. 1 3/8" input and 31 spline output. but it depends on what year it is. but I and many others run NP435's with 33in tires and 3.50 gearing and its a good setup. 1st gear is great for crawling only use lowrange in the t case for really rough stuff and 2nd gear is lower than the stock 3 sp so take off is better was well. Yes you can swap out input and outputs but really you should be able to find a 2wd F250 down tranny that will work for cheaper. Still have to check the output shaft as a lot of the later models (mostly 1980's have 31 spline outputs) I can usaully get them for less than $100 and i wouldnt pay much more unless I really needed it.
The NP is one of the cheaper swaps just need the adapter nothing else changes with exception of a larger hole in the tunnel and you have to bend the shifter to clear the dash. but still it can be a cheap upgrade just that a lot of people dont like the way it shifts becuase its not a sporty transmission.
The ZF tranny requires a lot of mods, crossmember driveshafts and convert to hydraulic clutch not to mention that if your running 3.50 gears you will need to change the axle gearing to be able to make use of the OD gear. In the end a ZF is going to cost you around $2k to swap in.

I've got a rebuilt 435 with the SB bellhousing, an NP205 transfer case, and drive shafts for this swap if you're interested.