Welcome back to the forums! Looks like we lost a couple weeks' worth of posts, so I'm going to recreate the topic I posted this past weekend. I recently got my '64 "Parts Dart" put back together again; I figured if you're gonna have a whole extra car's worth of spares, it may as well be functional. My friends and I are planning to turn it into an art car. Unfortunately, the transmission is having a problem.

The push-button 904 in my '64 Dart (parts car, not race car) will not reliably go into neutral. If the behavior was only off in one direction, I'd think it was merely the shift cable out of adjustment, but it's not like that. The reverse button gives you reverse gear, the drive button gives you forward gear, but pressing the neutral button from either of those positions will generally leave the transmission in whatever gear it was in, i.e. shifting from R to N leaves it in reverse, shifting from D to N leaves it in drive. The only exception to the above was the one time on a recent test drive that I shifted from R to N (it stayed in reverse) and then after coming to a stop I immediately pressed D, whereupon the car went into neutral. The trans shifts just fine otherwise. In drive, it upshifts all the way to 3rd and kicks down like it should.

It's almost like something inside the transmission is hanging up. The FSM has the following possible causes in the Service Diagnosis section under "Drives in Neutral:"
(A) Incorrect control cable adjustment
(B) Valve body malfunction or leakage
(C) Rear clutch inoperative

I think we can rule out A, because I followed the FSM adjustment procedure to the letter when installing the shift cable. Also, it stays in gear when shifting into neutral from either R or D. I would think a misadjustment would throw everything off in the same direction.

We can also rule out C, because the transmission reliably shifts into both forward and reverse gears.

That leaves us with "valve body problems," which should be fun and a half to diagnose and fix. My plan as of now is to drop the pan and take a good look at the mechanism where the shift cable attaches to see if there's anything hanging up or otherwise obviously wrong from a mechanical standpoint. If everything there appears copacetic, I'll remove the valve body and clean it out. My friend and I will use the hydraulic diagrams in the FSM to try and narrow down where the problem might be.

I'll also take a good look at the transmission fluid and see how much gunk is in there. The fluid and filter are new, but the torque converter in this transmission came out of the transmission in my race car, which ate all its clutch material and a bit of metal as well when we ran it out of fluid at Sebring last year. So it's very possible the valve body on this transmission is just clogged with clutch dust and iron filings.

Does it sound like I'm on the right track here? I'm open to any and all suggestions.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

make sure the valve body is a 64 valve body, and not a 65. They are different. A 64 valve body has 5 detents, a 65 valve body has 6 detents.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

This weekend, my buddy and I hooked up some shiny new harbor freight gauges to the transmission test ports to see if we could get any more data before pulling the valve body off. Line pressure, front servo pressure, and throttle valve response all look good. Didn't bother checking governor pressure since it shifts fine in Drive.

I dropped the pan yesterday but didn't get around to removing the valve body yet. The pan did in fact have quite a bit of fine metallic material in it. The fluid, while still dark red (not brown), was pretty opaque. Since the fluid was almost new and the car has barely been driven since then, I'd assume this stuff all came out of the torque converter. That's one way to flush it out, I guess. Still, the more I think about it, I remember that this transmission had the same issue when we briefly ran it in the race car with its original torque converter. Maybe not as extreme, but it definitely wouldn't shift into Neutral from Reverse. So the problem likely predates the filthy torque converter swap.

From looking at the FSM diagrams, the only thing in the valve body itself that could be wrong is the manual valve. I don't know if it's common for the bore to wear out or what. Maybe it was already gummed up when I bought this car and the added crud just made the problem worse. Could also be something external to the VB, like a bent lever or a missing/damaged check ball.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Okay, so apparently it was an adjustment issue after all. I followed the FSM adjustment procedure, but for some reason that just didn't sit right with this transmission. Before I dove into removing the valve body I decided to verify function of the shift cable and manual lever. Here is a video. Pay attention to the position of the lever with respect to the neutral safety switch (right side).

https://www.youtube.com/watch?v=UdyL8H8DILA

You can see how it's clearly off the correct neutral position when shifting into neutral from reverse. It does manage to get into the correct neutral position when shifting from drive, which jibes somewhat with the observed behavior while driving, i.e. sometimes it would actually shift into neutral from drive. I guess it sometimes had just enough movement to catch the detent, depending on how forcefully you pressed the neutral button.

Remembering a tip from someone on this forum (probably Doc), I proceeded to adjust the cable by eye so the manual lever lined up correctly with the neutral safety switch while the neutral button on the dash was held in. I had to move the adjuster wheel about 1/8" inward (clockwise rotation) from where the FSM procedure got me. More like the 25th hole from bottomed out, rather than the 5th. I then checked function again, this time with help so I could actually hold the camera:

https://www.youtube.com/watch?v=BpuanJ9l3gs

Looks good to me. It catches the correct detent in both directions now. Now I just need to put the pan back on and road test it.

I have to wonder why the FSM adjustment procedure wasn't sufficient on this transmission when it's always worked fine on the race car. Maybe the manual valve is worn in some way that allows it to bottom out deeper than normal when the cable is pressed into the case?

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Can now confirm that the car drives and shifts fine.

Lessons learned: Don't assume the FSM adjustment procedure will always get every transmission dialed in correctly, and the neutral safety switch is indeed a good reference point if necessary.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Great Videos! I am always fumbling around in the dark on the ground, doing the same thing by feel!(by myself)

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1964 Dart GT