Won't stay in park?

bluebetty

bluebetty

Member
Hello! I'm having some trouble with getting my 55 Special (dynaflow) to go into park. Sometimes it will "act" like it's in PARK but as soon as you cut the engine, it rolls. Or, it won't roll, but when I give it a shove to check, then it rolls. It *seems* like it goes into park better after it's gotten warm.

Any ideas?

Ps. I know very little about transmissions, so simpler terms would be helpful...

Pps. I don't have rear brakes (capped off entirely until I get around to it) so I am 99% sure I also don't have a parking brake... right?
 
This is what we do. When it's actually in PARK, it stays in park. I'm just wondering what could cause it to not go into park in the first place...

The brakes are on the list, just have to find brake lines and figure out what to do about the master cylinder, because the last owner converted to front disc and just capped the rear entirely, and my understanding is that I now need to put in a dual master cylinder.
 
Hi, bluebetty! There's a couple of main reasons that an automatic won't "park".

One is - misadjusted/worn/bent/whatever shifting linkage (or the whole transmission/engine combo has moved?) - you move the shifter to "park" but the selector on the transmission doesn't actually go fully into "park".

The other is actually something going on in the transmission - like the parking pawl (which is a little tooth that engages with a gear in the transmission) doesn't actually fully engage, or is worn away, or whatever. USUALLY, but not always, if that is the case: When the car rolls you'll hear it clicking kinda like a ratchet.

So, when it doesn't "park", what happens? It just sits in neutral?

Here's an adjustment question - when you shift from Park to Neutral - can you get the car to go into Drive by wiggling the shifter *without* moving the pointer over to Drive? Alternatively, when you shift from Drive to Neutral, does the car seem to want to stay in Drive until you move the pointer almost to Park? Those would tend to support the first scenario.

The 2nd scenario - I don't THINK that's the case because you didn't mention hearing it clicking, but...worth checking.

If you're lucky, it's just a matter of making sure that "park" on the shifter equals "park" on the transmission (adjusting the shifter linkage a bit so the "throw" will fully engage Park, while still letting you hit Reverse).

1722613906014.png

(Edit - Look in GL03's link to the 55 manual...there's a section on adjusting the Dynaflow Shift Control Linkage.)
 
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As for your brakes - you MIGHT still have a parking brake. If the shoes are still there, and all the cables and levers are all hooked up, then the parking brake could still work. The parking brake doesn't use hydraulics, it's all cables and springs, so it might still be fine, unless the previous owner gutted the system in the process.
1722627250785.png1722631295419.png
The cable, brake lever, and strut are what makes the parking brake grab.

(Just keep in mind, you're talking to a guy who still hasn't worked up the gumption to test the parking brake on HIS car! ;))

On the other hand - getting brakes to work "right" when doing a disc swap? That is a different conversation, and probably deserves its own thread!
 
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bittmann said:
Hi, bluebetty! There's a couple of main reasons that an automatic won't "park".

One is - misadjusted/worn/bent/whatever shifting linkage (or the whole transmission/engine combo has moved?) - you move the shifter to "park" but the selector on the transmission doesn't actually go fully into "park".

The other is actually something going on in the transmission - like the parking pawl (which is a little tooth that engages with a gear in the transmission) doesn't actually fully engage, or is worn away, or whatever. USUALLY, but not always, if that is the case: When the car rolls you'll hear it clicking kinda like a ratchet.

So, when it doesn't "park", what happens? It just sits in neutral?

Here's an adjustment question - when you shift from Park to Neutral - can you get the car to go into Drive by wiggling the shifter *without* moving the pointer over to Drive? Alternatively, when you shift from Drive to Neutral, does the car seem to want to stay in Drive until you move the pointer almost to Park? Those would tend to support the first scenario.

The 2nd scenario - I don't THINK that's the case because you didn't mention hearing it clicking, but...worth checking.

If you're lucky, it's just a matter of making sure that "park" on the shifter equals "park" on the transmission (adjusting the shifter linkage a bit so the "throw" will fully engage Park, while still letting you hit Reverse).

View attachment 16157

(Edit - Look in GL03's link to the 55 manual...there's a section on adjusting the Dynaflow Shift Control Linkage.)
Click to expand...
After more investigation, my husband figured out that if you go from drive directly to park, it will go into park and stay. If you stop at neutral first, it will not.

If you go from neutral to park, the car will start rolling very slowly forward. Or, in one case I shut it off and it rolled backward after I shut the door 😩

I cannot wiggle it from neutral to drive, and there is no clicking, just a hard clunk when you put it in reverse. I've read to never ever put it in reverse unless fully stopped, and it seems to go easier the harder I'm on the brakes.
 
Hmm. That still sounds like it COULD be due to slop in the shift linkage, potentially combined with a slight mis-adjustment which COULD be caused by the transmission moving around.

First thing I'd personally try is to see if you can adjust the shift linkage to give a little more "throw" in the Park direction, so that it will reliably go into Park, and hope that it still solidly goes into Reverse. If so, that could band-aid around the issue for a while.

(Assuming the "real" fix would be what - replacing thrust pad / engine mounts /etc. to more firmly hold the engine/transmission in place? Finding where there's slop in the linkage and eliminating that? If anyone has fought this sort of thing, they'd be better positioned to tell you where to look, not just "what sorts of things to look for".)
 
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