Bali26

Hi,
Title says it all. My 91 LS400 makes a Thunk sound when i take it out of park when its on incline or a decline. Not on perfectly level ground.

Its like the drivetrain is under stress and removing from P unloaded it. The sound kinda comes from rear of car.

Anyone help? Thanks.

Bali

PureDrifter

iTrader: (10)

trans/motor mounts and/or rear driveshaft bushing.

or next time, try putting the car in neutral, applying the parking brake, THEN putting it in park.

Bali26

If I use parking brake then no, there is no thunk. The mechanism that locks up drivetrain in P seems to be holding the weight of the car on incline. Is it supposed to be like that?

I'm will change the motor mounts anyday now will post pics for sure. Just thinking what other bushing i might need to order for the "thunk" from carson's.

Sixdown

To prevent the thunk, always use the parking brake first before you shift into park. I also have a mild thunk if I don't use the brake, and I also thought it was some mechanism that locked the drivetrain that made the noise, not a bushing.

Neofate

iTrader: (1)

It is the drivetrain. When we leave it in park on ANY angled surface, even 2degree's.. it will shift forward or backwards respectively. A small angle is not a big deal. But on an incline/decline we definitely want to press in the Parking brake before letting go of the brake in Park.

There is no special 'alternate' mechanism that locks the wheels when the igition is shut off,.. It shifts against the Park lock in the Tranny/drivetrain. All Automatics do it to a degree,.. use common sense on if the angle is too steep or not. A good rule of thumb is to just get in the habit of using your parking brake.

I use mine on anything but a flat surface.

*Yes, ANY of our cars will make a thunk of varying degree's on a straight incline being shifted into drive/reverse.. It HAS to shift that weight, nothing else is holding it. (Unless , of course, we use the Parking and Brake to keep tension off our transmissions)

Bali26

Thanks for the good information. So I need to start using P brake.