NP435 shifting strange
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Joined: Aug 2018
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NP435 shifting strange
So I had my NP435 rebuilt about 6 months ago by a trusted trans shop. Recently 3rd gear has been shifting a little hard and if I don’t put it into the gear slot just right it will grind. It has a new flywheel, clutch, new fluid in The trans and the clutch is properly adjusted. Any ideas what could be happening? Is that just the nature of the 435 or is something wrong?
Lead Driver
Joined: Oct 2018
Posts: 7,871
Likes: 2,360
welcome to my world. my NP435 shifted good and was in good condition but since it was out I took it to a good shop and had them put a Novak rebuild kit in it. just cause. I didn't like the fact the syncro's were made in india but I couldn't find anything better so I went with it.
Now it shifts like crap and does basically what you're saying. it's hard to get in 2nd and it grinds in 3rd.
I think it's the junk syncro's but I don't know. my shop says keep driving it will get better I don't see any improvement so I think I'm going to swap it out for the one in my shop truck I never use.
Now it shifts like crap and does basically what you're saying. it's hard to get in 2nd and it grinds in 3rd.
I think it's the junk syncro's but I don't know. my shop says keep driving it will get better I don't see any improvement so I think I'm going to swap it out for the one in my shop truck I never use.
Laughing Gas
Joined: May 2011
Posts: 855
Likes: 40
From: SoCal
My 80 F350 had the NP435. It was tough as nails. I had a problem once with it not shifting smoothly with lots of grinding. Long story short, it turned to be the release fork mount. It was worn out. I replaced the fork and the mount no more grinding. I can't remember if I had to pull the tranny to make the repair.
Fleet Owner
Joined: Jan 2004
Posts: 26,007
Likes: 575
From: Brentwood,CA
So I had my NP435 rebuilt about 6 months ago by a trusted trans shop. Recently 3rd gear has been shifting a little hard and if I don’t put it into the gear slot just right it will grind. It has a new flywheel, clutch, new fluid in The trans and the clutch is properly adjusted. Any ideas what could be happening? Is that just the nature of the 435 or is something wrong?
Lead Driver
Joined: Oct 2018
Posts: 7,871
Likes: 2,360
Might be worth a try but don't get you hopes up. but I've tried several variations of 80-90 , I have 50W in it now and see no difference at all.
I think it comes back to the parts we have available today. hopefully someone can prove me wrong I don't want it to be hopeless.
I think it comes back to the parts we have available today. hopefully someone can prove me wrong I don't want it to be hopeless.
Fleet Owner
Joined: Jan 2004
Posts: 26,007
Likes: 575
From: Brentwood,CA
50w Trans oil (Not to be confused with engine oil) is good and so is a MTL like Redline MT90 which provides correct friction for the syncros. Look for a fluid that has API MT-1 cert. The easy to get ones are Delvac 1300 50w, Redline MT-90 or Lucas 50w Trans oil.
Lead Driver
Joined: Mar 2004
Posts: 8,922
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Third gear will grind if you go too far to the right of it's gate. If it has new synchronizers, then I would guess whoever rebuilt it didn't get it shimmed right.
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Lead Driver
Joined: Oct 2018
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The Redline was my first try because that's what I run in all my transmissions. then 80-90. then synthetic 80-90 and noe Valvoline 50W because that's what Novak said to try. really no difference in any of them.
Not sure how things were set up I just know the guy who rebuilt it is a well respected gear box guy. not that it isn't screwed up but I don't know anyone who's better.
Not sure how things were set up I just know the guy who rebuilt it is a well respected gear box guy. not that it isn't screwed up but I don't know anyone who's better.
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Lead Driver
Joined: Oct 2018
Posts: 7,871
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It's just 3rd gear really, but 2nd is often hard to engage from a stop. 4th is fine.
You really can't float because you don't feel anything except resistance, and then it either goes in or grinds. double clutching does no good either.
Sometimes I wonder if part of it isn't in the tower. it was rebuilt too, it just has a real notchy feel to it. the best way to explain it is as if as soon as the stop ring gets any pressure it locks in place and if the teeth aren't aligned it won't let them move to line up.
You really can't float because you don't feel anything except resistance, and then it either goes in or grinds. double clutching does no good either.
Sometimes I wonder if part of it isn't in the tower. it was rebuilt too, it just has a real notchy feel to it. the best way to explain it is as if as soon as the stop ring gets any pressure it locks in place and if the teeth aren't aligned it won't let them move to line up.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 785
From: Simi Valley, CA
NP435 has nylon inserts on the 1-2 & 3-4 shift forks. These crack apart/disintegrate, the pieces can fall down into the gears, jamming them up.
1-2 inserts are different than 3-4 inserts. These are obsolete, but there are 100's available NOS and are also available from auto parts stores.
1-2 inserts are different than 3-4 inserts. These are obsolete, but there are 100's available NOS and are also available from auto parts stores.
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