I own a 1997 Ford F150 (5.4 liter V-8) 4 wheel drive that has 106,000 miles.
I rarely drive it nowadays but had hoped to keep it going (primarily for snowplowing in the winter).

I purchased it used in 2003 and within a couple of years, had a rebuilt transmission installed.
So, that had resolved the transmission issues in the years since.

However, we now have a slightly different transmission problem.
When shifted into "PARK", the truck will "slip" ad slowly begin to roll (forward or backward) when the truck is on an incline. (you can hear the gear slipping sound when this happens.

I am interested to receive feedback to learn if this is common for this model... (and to have some idea regarding how much work and cost i it would likely take to resolve (and is it worth it)

 

Sounds to me like the parking pawl is not fully engaging. I'd just make sure the parking brake works and use that too.

 

Thank you. I appreciate receiving your response.
As you suggested, I have recently been using the parking brake. However, I find it difficult to remember to do that each time I park. Especially since I normally drive one of two other vehicles (that don't require use of the parking brake.
So, Ultimately, I hope to be able to have someone fix this if it is somewhat reasonable.
Thanks to your message, I am aware of the term parking "pawl" and can visualize it (having looked at Parking Pawl images online).
Thank you.