W140 1997 S500 make a sound like the key is turned to start when shifting into park
 

My wife Informed me twice before that when she shifted into park the car made a sound like it would if you accidentally turned the key to the start position with the engine running. I couldn't reproduce it so I figured she wasn't paying attention and had turned the key to start when she intended to turn it to off.

Today she came home and it happened again so I was able to witness it. I does exactly what she says. Her foot was on the brake, her left hand on the steering wheel and when she moved the shift lever to park with her right hand it sounded exactly like she was turning the key to start.

I had her turn the engine off then shift to park. I tried to reproduce the problem again, but could not do so even after 10 tries.

Has anyone ever heard of this or know what is going on? Very scary!

That is really odd. The neutral safety is inside the transmission and only "talks" to the transmission control module to allow the starter to engage when requested by the ignition switch so I don't think the starter is involved.

Has the car made any similar noises while driving down the road or any soft of random rapid "feels like a stick in bicycle spokes"?

This car should have a 5 speed electronic shift 722.6. There is a bushing between the input and output shafts that wears out, this allows the shafts to move radially to each other. This in turn overloads a needle thrust bearing causing it's cage to wear out and needle bearings to fall out. . . into the planetary causing gears to be jammed. I recently took apart a core unit with this issue.

I'd stop driving and pull the pan right away then look for 1/8" diameter x 1/4" long steel rollers and some bits of sheet metal from the cage. The pan has a drain, the gasket is reusable and you can use a paint strainer to filter the fluid and dump it back in if nothing is found.

I've pulled the pan on a few a few high mile 722.6 that apparently never had a fluid change ( the filter molding date was prior to the trans build date. ) and there was zero material in the pan save for a slight evenly deposited film.

trans shifts perfect and is very quiet
 

It shifts very smooth and is very quiet. It only made the sound when she shifted front drive to park. As soon as she shifted back to drive the sound stopped. She shifted to park a second time and it did it again. However, once the car was turned off and started again it wouldn't. do it again.

bolo:

Consider trying a couple of other moves: when stopped in D, move the selector to N, pause for a moment, move to R, pause, and then to P. Was the sound heard in N or R before reaching P?

In park / neutral the trans input shaft, front planetary and torque converter are rotating where in drive or reverse they are not.

Wire up a light to the starter trigger wire, this way you will know for sure if the starter is being engaged. You should be able to pick this up at the under hood box on the passenger side, the wire should be purple if I recall correctly.