NP-435 4 speed grinding into 3rd gear

[Shran]

Anyone ever run into an old 4 speed manual, an NP435 in this case, grind going into 3rd gear?

This trans in particular would have come out of a late 70's F series truck. It is currently residing in my V8 swapped Ranger. I am having a hard time figuring out if I am dealing with an issue of the clutch not releasing completely or a transmission issue. I had a different trans in this truck which worked fine but leaked a lot so I cleaned up a spare I had and swapped it out, and put a new clutch and flywheel in at the same time. Now I am dealing with this grinding issue with 3rd gear. It is also often a tiny bit difficult to get into 2nd gear when stopped but usually not 1st or reverse, although those two gears often seem kind of bound up (if I want to use reverse, sometimes it won't go in unless I hit 1st or vice versa... but this seems to be a somewhat normal trait of all NP435s I've had.) The truck does not try to creep forward in any gear with the clutch pedal pushed in.

If this was a Ranger trans I would be for sure expecting a hydraulic issue and that would be great if that's what it ends up being... I have just changed so many components here that my mind is leaning toward something else.

 

[Rowdy Fitzgerald]

I used to have a 435 in my V8 swapped ranger before I went to a ZF 5 speed. The low range is fantastic! It was my experience that if it goes into first, second and reverse with little to no difficulty then the clutch is working correctly. I suspect you’re either not reaching the right rpm range (sweet spot) when shifting or the synchros are going out. But since you’re familiar with driving the 435 I think it’s probably the synchro that’s bad.

 

[rusty ol ranger]

I agree with the above. But it wouldnt hurt to check clutch adjustment first.

 

[Roert42]

My first thought was a synchro issue as well.

Could try shifting without the clutch. See how well it goes in.

 

[bobbywalter]

What clutch system are you using?

 

[Shran]

What clutch system are you using?

mid 80's F150 flywheel, clutch disc, pressure plate, bellhousing, clutch fork and throwout bearing
Trans: late 70's F series
Hydraulics: 86 Ranger master cylinder and hose, Speedway push type slave cylinder

I drove it a lot the last few weeks and it kinda comes and goes. Hot or cold doesn't seem to affect it much. Shifting without the clutch usually does not grind although it has a few times. It is usually pretty easy to get into 1st, 2nd or reverse. Sometimes it's not, on rare occasions I have to shift into and out of several gears to be able to shift into 1st or reverse - I have always kind of assumed that is the nature of the beast with these particular transmissions.

I may try unbolting the master cylinder and seeing if I can gravity bleed it better. Not sure how I would have ended up with air in there as it has worked fine for years but who knows. I am kind of at the point where I think there may be multiple things going on - first and foremost I didn't replace the 3/4 syncro and I probably should have, I even have it in a box but everything looked so good that I left it alone. Additionally I kinda think there may be something weird with the top cover/shift rails/forks... 3rd gear not only grinds but it's kinda hard to find to begin with, you have to hit the sweet spot where it just slips in... if you miss it, you hit a wall or grind the gear.

My wife put a hundred miles (trail miles at that!!!) on it over labor day weekend and I think she's better at finding 3rd than I am.

 

[Shran]

I used to have a 435 in my V8 swapped ranger before I went to a ZF 5 speed. The low range is fantastic! It was my experience that if it goes into first, second and reverse with little to no difficulty then the clutch is working correctly. I suspect you’re either not reaching the right rpm range (sweet spot) when shifting or the synchros are going out. But since you’re familiar with driving the 435 I think it’s probably the synchro that’s bad.

I am leaning toward a worn synchro too. I've had a bunch of these transmissions and put a ton of trail miles on them... they either work really nice or have some stupid quirk like this one does. If you find a good one, they are damn near bulletproof.

Out of curiosity. What did you use for clutch hydraulics?

 

[bobbywalter]

Fork condition?

 

[Shran]

Fork condition?

I looked them over pretty well when I had it apart and they looked great. Zero major wear on the pads. Top cover assembly in general seemed nice and tight and in good shape.

 

[bobbywalter]

Seen them bent and get crashy...they looked perfect. Your setup sounds ideal...

 

[rusty ol ranger]

I thought the 435 had a mechanical clutch? Or did they switch later on?

I know they lasted up through like 91.

 

[bobbywalter]

I thought the 435 had a mechanical clutch? Or did they switch later on?

I know they lasted up through like 91.

They are bothy.....

There are several external style slaves...the plastic ones suck....better off wilwood or his speedway setup.

 

[rusty ol ranger]

They are bothy.....

There are several external style slaves...the plastic ones suck....better off wilwood or his speedway setup.

Gotcha. My 83 had a mechanical clutch but now i think about it it had a T18

 

[Shran]

82/83 or so was the end of mechanical clutches. My bellhousing came off a T18 and IIRC it was out of an '82. T18, T19 and NP435 bellhousings are all interchangeable. I think they quit using the NP435 in the early 80's... I have seen some in 80/81 trucks but never after that, I don't think.

I like the T18/T19 transmissions a lot more, they shift much smoother and are just as durable but the first gear ratio is substantially taller.

 

[rusty ol ranger]

82/83 or so was the end of mechanical clutches. My bellhousing came off a T18 and IIRC it was out of an '82. T18, T19 and NP435 bellhousings are all interchangeable. I think they quit using the NP435 in the early 80's... I have seen some in 80/81 trucks but never after that, I don't think.

I like the T18/T19 transmissions a lot more, they shift much smoother and are just as durable but the first gear ratio is substantially taller.

My 83 had a 300 with a 4.10 rear. Im guessing the rear wasnt factory as it was an 8.8 and not a 9 inch. Either way in 1st with the T18 that thing would move about anything. IIRC the T18 had a 6.32:1 first and a stupid low 7: something reverse. It was awesome for backing up heavy trailers. Just let off the clutch and you didnt have to touch it again till you had to stop.

I think the 435 had a 5.16? To one 1st....somewhere in that neighoorhood.

So was it the NP435 then they ran with up to the early 90s? I know you could get a creeper 4 atleast till 91, maybe 93 IIRC. They got rarer though after 87 or so,