I give up, why?

Sixto
87 300D

What do you mean, why?

I mean I don't know why people offer unwarranted advice in general and with good intention in particular.

Sixto
87 300D

To CN;

My condolences.
I've been reading this thread with some interest in the technical problem you pose, and also, unfortunately, with not a little cringing.

Although there are, as you note, electric solenoid stops/locks available, allow me to offer this as a concept. I have been examining a shift mechanism from a 114/115 (similar to 123 in this area) chassis that I have on the shelf, and it would appear that a latch and release device can be created that would be released by hydraulic force from the brake system. A small cylinder could be actuated (from either of the brake circuits) to lift a latch out of the way of the shift arm below the floor of the car. The device would be mechanical (like the cable type), rather than dependent on electric power, and would conform to the present style in that it would be linked to the brake pedal.

Do you know where I might find a suitable cylinder actuator? I hadn't thought of a hydraulic one, but there's no reason it wouldn't work. Thanks.

Some stick shift Subarus have a hill hold function that keeps the brakes applied even when you take your foot off the pedal until you apply throttle. Lets you start up a hill without keeping one hand on the park brake lever. Such a car might have the hydraulic actuator you need.

Sixto
87 300D

I do miss having the shift interlock that I had with my E320 Cabriolet. I've forgotten to put my '87 300D into park a handful of times now.

CN:

I had offered the idea on a concept basis, deliberately avoiding any detail.
A quick look in a few catalogs indicates that stock sizes are generally available down to a bore size of 5/16". Stroke lengths are available down to 1/2". With that info in hand a design exercise could be undertaken.

It's usually a bad idea to tap into the brake system like that. Trailer brake controllers that tied into the brakes were outlawed for safety reasons.

Rube Goldberg might install a 70s Saab console key switch :)

Sixto
87 300D

Wheel chocks would be the simplest and most reliable solution.

Something simpler but not as effective: when you put it in park, make sure the car's weight is loaded against the park pin, and then set the e-brake. For example, when I park on a hill, I set the e-brake first, then put it in P. If you put it in P first, then try to take it out of P, you hear that loud slam, and pulling it out of P takes a lot more strength. The kid might not have the strength. And if he does, the loud noise could scare him into not touching anything else, like the e-brake.

Have you thought about putting some kind of lockout on your e-brake release? It might be a ton easier!

If you really want to mess with some diy shifter lock, I'd highly recommend something electric and not hydraulic. Two electric things you might try:

- some kind of solenoid that will physically block the shifter from moving out of P, and it can be wired to the tail light wiring.

- use an electric shifter like in hot rods. It will replace your whole shifter with an electric servo that will select your gears by the push of a button. And the buttons don't work when the car is off.