Rebuilding the NP435
Ford and Dodge’s premier Granny 4-speed
The NP 435 transmission is one of the most popular heavy-duty "Granny-Geared" four speeds that was ever offered from the factory. It came in several -, -, and 1-ton 4x4 trucks from Ford and Dodge, ranging from the early 1960s into the early 1990s. The NP435 is the only granny geared 4-speed with an aluminum top cover, making it easy to identify. The ratios for the Ford NP435s are: 6.68:1 First; 3.34:1 Second; 1.74:1 (or 1.66:1) Third; and 1:1 Fourth with a 8.26:1 reverse. There is a Dodge version with a taller 4.56:1 first that is much less desirable for off-road use. Transfer case adapters for the Ford and Dodge NP435 are available to mate the transmission to the Dana 18, Dana 20, Dana 300, Toyota trucks, and most of the popular Jeep New Venture T-cases (NV231, NV241 etc. ). The transmission is found from the factory ahead of the Bronco Dana 20, Ford NP203, Ford NP205 transfer cases, and NV241s in some Dodges.
To re-build our NP 435 we reached out to the folks at Novak Conversions (http://www.novak-adapt.com/) because they are the experts on rebuilding this manual transmission, as well as many others. They also have comprehensive rebuild kits with detailed instructions that cover tools, lubricants, cleaning, and inspection best practices. Those things are a must-have when rebuilding older transmissions or transfer cases. They also have gobs of information on adapting the NP435 to all kinds of engines and sell adapters to mate 2WD and 4WD versions of the Ford and Dodge NP 435s to most of the commonly used transfer cases.
Which Transmission to Use
Our NP435 is a Ford 4x4 unit we found for sale on the internet, but adapters are available for both the 2WD and 4WD versions of this transmission. There are a few differences between all of the NP435s; most are insignificant but might be important depending on what engine you plan to use in front of the transmission. Some NP435s have "bonus ears" cast into the front face of the transmission. These are undrilled mounting ears that might help you adapt your NP435 to your engine of choice.
Where to Start with a Ford NP435
We started the process of rebuilding our NP435 by completely disassembling the transmission. The instructions from Novak cover disassembly well. From there, it's time to clean things up. We recommend soaking everything in a parts washer for a few days.
The first step towards re-assembly is to clean and reinstall the transmission case magnet. Ours was retained with a metal clip, but you can epoxy the magnet to the floor of the transmission case. From there, you can install the reverse idler and idler shaft, and then install the transmission counter shaft. But first, we installed the new bearings from the Novak rebuild kit. We were able to remove the rear countershaft from the removable aluminum housing with a little work from a Dremel tool with a cut off wheel and a few whacks of a chisel.
NP435 Mainshaft Assembly
From here, we begin reassembly of the main shaft. We start by installing the second gear with its replacement synchro assembly, spring and retaining spring. From there, the gear can be slid onto the shaft, and the special split snap ring retailer can be installed into the groove with a large pair of adjustable pliers.
Then, third gear can be installed on the main shaft with some of the third- and fourth-gear synchronizer shims. These will adjust the endplay of the input and main shaft, following the procedure outlined in the Novak rebuild instructions and a feeler gauge with the main shaft clamped into a vice.
The hardest part of the NP435 rebuild for us
Installing the first/reverse sliding gear on the main shaft was probably the hardest part of our transmission rebuild. There are two anti-rattle clips that have to be held in place in two of the 10 large splines on the inside of the gear using assembly grease (recommended by Novak and us after this) or frozen Vaseline (what we had). The trick is that two of the teeth are narrower than the other 8, and the anti-rattle clips have to be held in place on the side of these teeth with the inside of the C facing the side of the tooth (see picture, though the grease isn't helping with seeing the clip). Eventually, after you reposition the clips several times, hold your tongue just right, and say your prayers and chants just so, the first gear will slide into place on the main shaft.
NP435 Mainshaft assembled go to your home!
This is the reassembled main shaft with all its components. There are is a thrust washer on the front of the main shaft, where the input shaft will ride and a spacer ring in the back of the main shaft that will keep the rear bearing spaced away from the main shaft properly. With all this in place —helped by some assembly grease or Vaseline—we have to get the assembly back into the case. You might get this in one shot, or take a few goes at it. Just make sure the thrust washer and spacer ring don't fall off or get dislodged on the way in.
NP435 Input Bearing Retainer
The rebuild kit from Novak comes with these selective "service gasket shims" that help you set the endplay of the input shaft of the transmission, per the instructions. We also removed the tapered roller bearing from the front of the input shaft using an axle bearing puller tool. In addition, we replaced our input bearing retainer with one that had been turned down to fit with our bell housing; otherwise, replacing the tapered race in the input bearing retainer can be a bear of a job, but the Novak instructions tell you what to try. We then checked the thrust washer on the front of the main shaft and installed the new roller bearings and retaining ring into the back of the input shaft.
Final assembly of the NP435
From here, we installed the adapter and rear bearing on the main shaft after checking the position of the spacer ring on the back of the main shaft. That ring can get out of place and get stuck between the shoulder it is supposed to ride on and the rear bearing, which will damage it or the bearing.
NP435 top cover and shifter cane
Our top cover cleaned up nicely, and the forks moved easily, so we decided to test install it and then reuse it. We did however clean it all up, re-lubricate the areas where the shift rails move, and replace the plastic fork shoes on the tips of the three forks. Also, our shift cane installed into the top cover easily and seems to lack slop. Novak also carries shifter canes, a shifter retention kit (with a new inner boot), and top cover rebuild kits that include everything you need to make your NV435 shift like it did when it left the Ford factory. Wait, did we mention the tons of information and parts available from Novak Conversions at www.novak-adapt.com?