That NP435 is a HD 1:1 final drive trans, with, as you have found out, an extremely low non-synchronized first gear. That is a grain-truck trans, suitable for hauling heavy loads over soft dirt fields.
However, the other gears are not that bad and, the 1/1 final is the same as any other manual...
I would be leaning towards either a fuel-pressure issue, or a failing EGR system.
A scanner should reveal the problem, but without a code, you will likely need a good EFI technician to decipher the results.
The fuel-pressure issue could be as simple as the pump sucking air.
my big fat mouth has cost me a lotta money over the years. If I said I would do it, I had to do it. I'm a lot more careful what I say now. Actually, I learned to think things thru a lil better; "let your yes be yes and yur no be no"; I learned to say no.
Those old trucks are huge and heavy bricks and they take power to push thru the air, and the faster you go, the worse it gets. So if you really want one of those, you are gonna have to figure out how to make it take less power to push it thru the air.
Here is some help; the rule of thumb is that...
You know what would help, is if you could list all your pertinent info, in your signature, so it appears on the bottom of every single post.
To do that go to the top of any page and find your name on the Top RH corner, clik on it and go down to "signature", then clik on that. Down will drop a...
Charm, yur not listening.
The vacuum advance does not work at WOT, there is not enough manifold vacuum to make it work.
And it MUST not work at idle. Because as soon as you step on the pedal, the vacuum will drop out, and your timing will go retarded.
That device must only work at Part Throttle...
WOT power timing is done without, without, without vacuum advance; as is the idle-timing; as are all timings.The Vcan timing is never considered part of the timing. It is purely a PartThrottle device to dole out advance in accordance to the load, to increase PT Torque, which helps increase PT...
OK gotcha with the electric choke;
but the bottom line is still the same; the valves have to close all the way, by backing out the speed screw.
I have never seen a carb on a Mopar, that could not be closed all the way; don't forget the secondary link rod; it may have to be rebent; that is why it...
Try not to get ahead of yourself.
The idle and low-speed circuit together with the idle and low-speed timing, have to be sorted out first. I often completely disable the secondaries, so they cannot interfere.
I'm not understanding this.
When quoting timing is should be accompanied with an rpm...
Don't get the Idle-speed screw or curb-idle screw
confused with the fast idle screw,
The curb is on the drivers side.
the fast idle is on the passenger side.
To check the t-port, the fast-idle cam must not be engaged!
The throttles should be able to close all the way; you need to fix this!
The problem could be;
the fast idle cam,or
the accelerator pump adjustment,or
the secondary linkrod.
the throttles must close all the way; do whatever it takes.
Sometimes the throttle valves are not properly set in the...
When you do a compression test, you know that you have to keep on cranking until the highest number is achieved at least twice,on the same cylinder..... right.
The open/ closed throttle is no big deal; it just takes a couple of extra revolutions to reach max. Unless, unless, unless; your...