Truss rod doesn't seem broken, but doesn't affect the relief at all

Rubbery wood. Sometimes really soft wood won't respond to trussrod adjustments. Just a theory as I can't see your bass.

 

Ok lets start at the beginning. How many turns did you turn the trussrod?

 

Actually, it's the other way around. It's a stiff neck, and a low budget truss rod. A common thing on mass produced instruments. The neck is made from a hard board, and is relatively thick. The truss rod is along for the ride, and isn't really strong enough to do much of anything. On a neck like that, you can't really adjust the relief. Significant problems have to be corrected by fret leveling, fingerboard resurfacing, etc.

A soft rubbery neck will respond easily to truss rod adjustments. And tuning key adjustments. And the movement of the moon.

Remember that stiffness and stability aren't the same thing. A stiff neck can still develop a nasty bow or backbow or twist, just from the gradual drying of the wood. And it will take a lot of pounds of force to pull it straight. That's how truss rods get broken.

A soft rubbery neck can be stable, if it's built well. You have to fuss with it to get it adjusted for a particular combination of string tension and setup, but then it will be stable at that setup. Rickenbackers are a classic example of this.

 

Have you run out of adjustment room?

 

if desperate, try keeping the strings completely slack for 48 hours while the truss rod remains under tension and see if the neck moves any after that.
if so try bringing the strings up to pitch slowly. d standard first, then wait 24 hours. then e flat standard and wait another 24 hours. you're just checking on neck movement and relief here.

as the great american philospher tom petty once said, 'the waitng is the hardest part.'

 

I understand what you're saying, but many of the CIJ Fender basses I've owned have young cut maple for the necks, and they don't respond correctly to truss rod adjustments. Those are the experiences I've had and what I was referring to. I've had them where the wood was so soft that the trussrod just squashed the wood inside instead of making neck move, and others where a truss rod adjustment only moved the neck up by the head stock. The earlier MIJ Fenders (Made instead of Crafted in Japan) didn't have that problem.

 

STOP!!!

If your truss rod nut feels like it has stopped, OR if you cannot see or feel any change in the neck relief, don't keep torquing on the nut.

1. Take the truss rod nut out and put in a washer or spacer to give the truss nut a little more room to tighten up. I found 1/4 aluminum spacers at my local Ace Hardware store that fit's my Fender necks perfectly.
2. Build a jig to 'bend' the neck before you apply torque to the neck. I used two pieces of scrape blocks, a scrape piece of round oak dowel, a scrape piece of broom stick handle, and an old tube sock. I blocked the neck and the dowel, and used the tube sock as a tourniquet. Watch the video below. You can jump to 1:37.

Good luck.