Hello yall, I've been fighting issues with my np435 for a month now, I'm on my second trans with the same issues and I'm honestly lost.

I'm having pretty severe grinding issues in 1st and 2nd but is not the normal clutch issue where it grinds going in. When you shift into second is feels like it goes in but when let out the clutch it gets no power to the wheels and just grinds, this happens about 80% of the time so it's not just an "old truck trans thing," it's un drivable. Double clutching doesn't help nor dose shifter wiggling or putting in any other gear first. The only thing that fixes it is going into reverse, backing up and then back to 2nd, works everytime.

It's had this exact issue across both transmissions with only slight variation in how it feels and how often, I've tried all the basic swapping of the plastic fork feet and checking if bent or loose. I've ruled out the transfer case with a stethoscope, it is grinding in the trans. My only thought is top cover but from my knowledge everything seems right however anyone else's knowledge here on what to look for would be appreciated. Both were also checked for preload and were in spec.

I know people complaining about 435 issues is pretty standard and I've tried all the common fixes across both transmissions and had no success.

The vehicle as been swaped to a roller 351w out of an automatic 94 but I'm not sure if that would be related to this issue. Any ideas would be appreciated as I'm dead In the water on this one.

 

Well my first thought was the pads and bent forks not getting it all the way into gear.
As a guess did you use the same top cover & forks on both transmissions?
You did not tell us what year truck this is and if it has a hydraulic clutch or not?
Firewall moving when you push in the clutch?
Was the first NP435 also behind this same 351 auto motor?
Did you install a pilot bushing / bearing in that 351-auto motor? If not the input shaft can be moving all over the place and causing the problems.
All I got right now
Dave ----

 

I actually tried both covers on both transmissions and the new cover completely fixes 1st but not 2nd. It is and 85 flare side and yes it is a hydro clutch, I've run it with the cover off to confirm the clutch disengaged. Both were behind the roller 351 but on the factory 351 there wasn't an issue, I did install a pilot bearing and everything is new inside the bell housing.

I did check the firewall and it's sturdy, luckily a middle georgia truck it's whole life so no rust or weakening

Any chance the crank isn't recessed enough on the roller blocks for the input shaft?

Since there is a chance both my top covers have bent forks (however unlikely) any diagrams or photos of know correct forks?

I'm really starting to think Im just extremely unlucky and have 2 bent forks. I bought the truck recently and pretty much did the swap immediately after purchasing it and didn't put more than maybe 10 miles on the original setup. Unsure if it was a mild issue before but it was definitely an issue immediately after the swap.

 

If the transmission when all the way in and not pulled in with bolts the crank is deep enough, and I have never heard of one not being deep enough.

I know you car not to do this but think you have to to see what is going on.
Next time it happens pull the top cover but do not shift it into neutral so the shifting rings stay where they are when this happens.
You should then see if the rings are pushed all the way into gear or not. You can also try and move the truck when the grinding happens and see what is going on inside the trans.

I know when going into 2nd on a down shift my NP435 is a little hard to get into gear and the throw dose not feel right, kind of short, but never any grinding.
Now going into 3rd, up or down, I can feel some grinding, gear teeth hitting, even when I double clutch it as I do all the time going into 3rd.
Mine was used so dont know what shape it was in before I got it and just live with it for now.

I cant think of anything else at this time on yours.
Dave ----

 

What about the bolts securing the shift cover to the main housing?

A few years ago, I had some weird shifting problems with my T-18. Finally found the cover had worked loose. Some of the bolts had rattled out and and rest were very loose.

You mentioned recently swapping covers, so it’s highly unlikely the bolts have had time to work loose. But maybe the bolts are too long? They could bottom out and feel tight, but still let the cover move.

Just a thought.

 

Why are you shifting from 1st to 2nd? I would consider 1st a special gear that is rarely used in normal driving. 1st is too low in that transmission to be shifting to 2nd on the fly. The synchronizers will have a hard time matching the speeds. If you had to do it, I would rev the engine really high in first and get the truck going, and then push in on the clutch, pull it out of 1st and wait a little bit before trying 2nd. Normally you should be starting out in 2nd gear. 1st is only used for off-roading and special circumstances.

 

Heavy loads like pulling a 20ft enclosed trailer and having a 2.75 rear gear.
I find I use granny when in parking lots to start off so I dont need to slip, read wear out, the clutch because of the rear ratio.
Now on the road unless pulling the trailer I start off in 2nd and because it is a truck transmission there is no "speed shifting" it ever!

But he still should not have any problems if he wanted to use granny on the street, other than a PITA to shift, as 2nd should work all the time.

What lube are you using in the transmission?
I run Red Line MT90 as it is for older transmissions GL-4
Dave ----

 

I don't, I start in 2nd but it dose it in both unfortunately have the same symptoms

 

I run 50w

 

Just checked, all seem to be tight but that gives me an idea, can the gasket be too thick? I used the felpro and it is fairly thick

 

Thanks for checking. Maybe double check the bolts aren't bottomed out. This could happen if the main casting has blind holes for the cover, or the wrong bolts were used. The bolts will feel tight when turned with a wrench, but aren't actually clamping down properly.


I don't think that would make any difference. Even if the cover sits a little higher than stock, the forks should have plenty of meat for engagement with the shift collars.

One more thought: Are the shift forks secured with roll pins? If so, it's possible for a roll pin to shear but the short pieces remain in place. Find a drill bit or piece of stout wire close to the inner diameter of the roll pin. See if it will pass all the way through. If not, the pin is sheared.