85 f150. 300 np435 bw1345
I went to out the truck into gear to pull into a parking spot. (have the mild firewall flex issue) and heard a clunk. It was in 2nd but was as if was it neutral. Played with the shifter and got it into the parking spot. Now I'm not sure what gear it's in but it I start the truck an let go of the clutch the engine bogs down and it tries to roll forward but won't. Here's what inside the cover looks like.

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What should I try?

 

To clarify I went to put it in 2nd. It clunker the shifter was in second but the truck was in neutral. I messed with it and got it to pull forward. After pulling the shifter and playing with it for a min it now is stick in a gear, or two at once. It will try to inch forward then stops when the clutch is let out a bit

 

Don't panic!

You've got three shift rails side by side. When in neutral, the slot in each should line up next to each other. The rails have interlock pins (hidden) so that only one rail at a time can be moved out of neutral.

Currently, the center rail (3-4) appears to be moved aft into the third gear position. Make sure the parking brake is set. Use the shift lever or a big screwdriver to move that rail forward to line up with the other two. If it doesn't move easily, depress the clutch to take any tension off the gears.

If that still doesn't work, chock the front wheels and jack at least one rear wheel off the ground. (Raise both rear wheels if it has a limited-slip differential.) That should guarantee all tension is off the gears.

If the center rail still won't budge, it could be the interlock pins have failed or jammed, and it's the outer two rails that are out of neutral, not the center one. (Reverse rail is on the left with the spring-loaded plunger in the slot, and the 1-2 rail is on the right) See if those two rails will work aft.

When you are done, all three slots should be lined up side by side. That will be neutral.

If the transmission still won't shift properly, it's possible a shift fork has broken or worked loose from its shift rail. Don't worry, as that's not the end of the world. You only have to remove the cover assembly for access to the shift forks.

 

Deleted. Previous post corrected. Moderator: please delete this post.

 

I managed to get the shift forks lined up with the transfer case in neutral. Installed the shifter and tried inching it in first and second. The I put it in neutral and released the clutch and the truck lurched forward and stalled. i unjammed it out of second again and got it into 3rd. Ill drive it like that to my garage where i have another transmission.

My only question:

With a np435 seperated from the transfer case, should the output shaft be able to slide the output shaft out? i was inspecting spar a few weeks ago and it slid out surprising me.

 

I'm not super familiar with the NP435, but that is normal for other 4 speed transmissions. The big bearing on the rear of the output shaft is sandwiched between the transmission and transfer case. Remove the transfer case and that bearing and shaft will slide aft.

Do NOT install that transmission until you carefully inspect the innards. The front tip of the output shaft rides on needle bearings inside a cavity in the input shaft. I can almost guarantee some of those needle bearings fell out and are sitting in the bottom of the transmission.

Back to your current transmission. From what you've described, with it still binding even with the shift rails aligned, you've probably got a loose or broken shift fork. All you'd have to do is remove the cover to be sure. If anything is broken, make sure you retrieve all the pieces. Hopefully there's no need to pull the entire transmission.

 

This is very helpful so far I appreciate it. At one point I did notice that the shift for on the right in that picture above, had a gap between it and the middle fork. That fork bay have broke. The tranny had also been popping out of 2nd the odd time if just putting around a parking lot. I'm thinking changing the cover may help.

Unfortunately it is practically against the floor so the tranny has to come out.

Thanks again for the help and the warning about the bearings.

 

Isn't there a removable panel on the transmission hump?

 

(Ignore this post my phone messed up)

 

Actually yes, I could take that panel out to get to the cover. A pain but I have had it off once before. I may do that.

I got the truck home from work about 2 km in second gear. I found a clue into the problem.

That gap shouldn't be there, I think you're onto something with the shift forks.

question now is, the truck is on the street and my garage full of tools and the spare tranny is about 20km away (mostly highway). What's the chance of there being debris in the tranny, and should I try to change the cover now or get it into 3rd gear and drive to the garage and pull the whole tranny?

 

I think the shift forks are cast aluminum. In your latest picture, it looks like lots of shiny specs present that were not in the first picture.

In theory, the steel gears should safely grind up any cast aluminum that gets caught, but is it worth the risk? Even if nothing jammed, it can't be good to create all those aluminum shavings. How about we take up a collection for a tow truck instead?

 

The shiny spots may be the camera on the flash. I wouldn't doubt that there's aluminum in it now. I'm going to take a good look through my spare transmission if it looks good I'm going to attempt to drive the truck as a tow call will cost me more than a tranny. I paid 50$ for the one it now 3 years ago, it pops out of second and grinds going into 2nd and 3rd sometimes so I have no feelings for it.

If my spare tranny is questionable, I'll tow the truck, clean the current one and change the cover.

 

Not sure about the NP435, but usually the shift forks are secured to the shift rails by roll pins. The damage may be as simple as a sheared roll pin.

 

After thinking about it for a bit, I pulled the cover off through the floor to inspect the forks. One is worm down by the looks of it. I'll take a hunch the cover is the issue. I'm going to get my other cover and see if it shifts. If it does I'll do an oil change before driving it and be on my way.



Thanks for the help