I just assembled and test drove yesterday a 1979 f250 with a np 435 and a 400 4x4. new luk clutch and new linkage resurfaced flywheel new pilot bearing and throw out bearing. I have not fine tuned the clutch adjustment yet as it feels like my issue is not clutch related. the np435 was disassembled, new synchros new bearings new input shaft new quill tube new nylon pads on shift forks cleaned and reassembled and refilled with 80w-90 clearances brought to spec, and installed in vehicle. The low slot (1) works as it should, the reverse slot works as it should, and 3-4 work great 4-3 work great 3-2 work great 2-3 work fine but stopped to 2 or 1-2 the shifter goes about half way through the range of motion and stops without engaging 2nd gear, about 1 in 4 or 1 in 5 tries it goes right into 2nd gear from first or from stopped, no grinding no shifter obstruction, does not feel like the shifter is bottoming out just not quite lining up shift. When rolling down road I can go from 3-2 and I hear the synchro spool up the gear then it drops right in and stays in gear. when you get it into gear from a stop it drives fine and stays in gear. A few of those clearances inside were out of spec and I did shim them to the middle of the range, but double checked after final assembly and it was not too tight, after all new parts wear in and the clearance almost always grows.

With the transfer case in N and engine running it behaves exactly same. I can put in 3 let out clutch and immediately drop to 2 but can't drop from 1-2 or n to 2 with engine running. I want to get under it double check fluid drive it once more, post if there are any ideas as to what this might be, I am leaning toward a bent fork or a bent rail maybe but open to suggestions.

 

Good chance it's the junk repop stop ring. you're lucky mine didn't shift in 3-4 decent either.

My original NP435 shifted okay but I wanted to rebuild it. had a hotshot transmission guy put a kit from Novak in it and it was undrivable. pulled it back out and went through it again and it still sucked. now I'm running a good use transmission until I get the NOS stop rings I found on ebay put in it and back in the pickup.

 

oh how nice. sounds like a do over then.

 

It could be something else, but this was my problem. as far as I know all new stop rings are made in India and poor quality. my transmission guy says he's run into this before and had to put the used ones back in. but I know guys who say theirs shifts great, so I can't say 100%.

I found NOS ones, I did see some old stock aftermarket ones for sale that might be okay.

 

I drove it again further and it worked much better, might be getting oil worked into the areas, 2nd became grouchy after several miles but it was much easier to shift the second drive.

 

I do have to agree with 440 that these new parts are not of the same quality as what the old ones were.
I rebuilt my 435 a while back using the same kit and it shifted great for a while. now after more milage and city shifting it shifts OK but I can tell
the difference esp. into 2nd.. No complaints yet but wish more attention was put to the quality of syncro parts......

 

IT is getting a little better, I will run a tank or 2 of gas and do a fluid change and see if it drains any mystery metal out. I will likely live with it through the winter and see if it gets more manageable.

 

I have about 500 miles on this transmission and it is almost totally gone this issue. I plan on change oil to new maybe lighter oil. Its working a lot better. I bet it just needed burned in to keep the synchro from locking the shaft. If you rebuild one of these, and it does not shift perfect, just drive it a bit and it might get better.