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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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.