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Topic: Auto shift Interlock

in Forum: C4 Driveline Components

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Auto shift Interlock (1/6)
4/7/14 3:20pm

cco
Former Member
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Joined: 8/16/2013
Posts: 191

Had a minor setback this morning on my way to get my Corsa , fan control and bushing:

Started fine, went to shift to R to back out of garage and wouldn't shift out of park. The knob at the top of the shifter (the release) would not depress and release the shifter (yes with foot on the brake).

It eventually did after several attempts -- but I looked for an override slot to release the shift lever manually and found none.

1/Is there a release should the interlock fail again, and 2/could the fob battery replacement have any bearing on this issue?

The fob is functioning properly now but its battery did die in the last couple weeks after bringing the car home from storage.

I have noticed that the interior lights take a minute or 2 to come on (with the door open).

Could the door switches have a connection with the temporary interlock failure?

I do have the FSM's but found nothing definitive on the problem. If the answers are in there and someone could lead me to the right section I'd appreciate it.

1994 vert - auto, 25k miles

Cheers,

Colin.

|UPDATED|4/7/2014 12:20:50 PM (AZT)|/UPDATED|

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Re: Auto shift Interlock (2/6)
4/13/14 7:32pm

cco
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Joined: 8/16/2013
Posts: 191

This sticking has happened a couple of times now and it took a few minutes of trying to depress the trans button to succeed.

I'm now thinking it's not a faulty solenoid, but it's a mechanical linkage connected to the brake pedal that may be sticking.

What also is strange was that with the car facing into my garage which slants slightly toward the door, the trans stuck a few times.

With the car backed in and leaning toward the door, the trans does not sick and shifts out of park just fine.

I take it that no one has had any issues with their auto trannys getting stuck in Park.

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Re: Auto shift Interlock (3/6)
4/13/14 9:23pm

Rod1991
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Vette(s):
1991 C4 Corvette Quasar Blue coupe

Joined: 9/2/2013
Posts: 16

Colin,

do you engage your hand brake before you put your transmission in park, this could reduce the load on the transmission park pin, allowing it to release easier.

Just a thought!

______________

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Re: Auto shift Interlock (4/6)
4/13/14 9:39pm

davep85c4
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Joined: 4/4/2009
Posts: 254

The shifter lock is entirely mechanical. There is a cable to the ignition switch (the electrical part of the switch, not the key tumblers) that is released when the key is rotated out of LOCK. There is a mechanical lever on the shifter itself that allows the shifter to move, when the cable retracts about 1/4". There is no "override". Rotate the key out of LOCK, and the shifter is supposed to be free.

There are NO electrics of any kind involved. The brake pedal has nothing to do with it either. Three mechanical components. The barrel on the ignition switch. The cable. And the lever on the shifter.
One of these is probably sticking. Most likely the lever on the shifter.

My C4 is a 4+3 and the shifter interlock is different than an automatic. However I have owned 7 GMC Syclones and Typhoons. SyTy uses the exact same shifter interlock components. I have had trouble with SyTy shifters, and it was always the lever on the shifter. Remove the console top plate, the shift boot, and figure it out. It's not hard. (The c-clip on the shift knob can be fussy).

I'd post a pic of the relevant shifter mechanism, as I have a bare shifter in my SyTy parts stash, but this site is way too damn fussy to post pics on. I won't even try. Waste of time.

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Re: Auto shift Interlock (5/6)
4/14/14 9:35am

cco
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Joined: 8/16/2013
Posts: 191

Rod1991 said: Colin,

do you engage your hand brake before you put your transmission in park, this could reduce the load on the transmission park pin, allowing it to release easier.

Just a thought!

That could have some effect on the shifter's release -- I hadn't thought of that .... tho the gradient is very slight.

I'll try the p/brake next time I park facing into the garage and see what happens.

After reading Dave's answer I'm leaning more towards this cable that runs from the shift lever to the ignition switch which releases the shift lever when the key is turned.

Sounds like it is binding and needs a good cleanup.

Thanks guys -- I did find the section in the FSM that deals with this subject and now it makes more sense knowing it's not electrical but mechanical.

You guys are the best. Thanks again.

Colin.

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Re: Auto shift Interlock (6/6)
4/14/14 9:37am

cco
Former Member
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Joined: 8/16/2013
Posts: 191

davep85c4 said: The shifter lock is entirely mechanical. There is a cable to the ignition switch (the electrical part of the switch, not the key tumblers) that is released when the key is rotated out of LOCK. There is a mechanical lever on the shifter itself that allows the shifter to move, when the cable retracts about 1/4". There is no "override". Rotate the key out of LOCK, and the shifter is supposed to be free.

There are NO electrics of any kind involved. The brake pedal has nothing to do with it either. Three mechanical components. The barrel on the ignition switch. The cable. And the lever on the shifter.
One of these is probably sticking. Most likely the lever on the shifter.

My C4 is a 4+3 and the shifter interlock is different than an automatic. However I have owned 7 GMC Syclones and Typhoons. SyTy uses the exact same shifter interlock components. I have had trouble with SyTy shifters, and it was always the lever on the shifter. Remove the console top plate, the shift boot, and figure it out. It's not hard. (The c-clip on the shift knob can be fussy).

I'd post a pic of the relevant shifter mechanism, as I have a bare shifter in my SyTy parts stash, but this site is way too damn fussy to post pics on. I won't even try. Waste of time.

No worries on the pictures Dave. I've got a good handle on it now and the FSM's to refer to also.

Thanks for taking the time to explain.

Cheers,

Colin.

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