TH400 guru's ... strange problem

[JoeliusZ28]

My friend is building a '70 GTO vert (clone). He is using a rebuilt TH400 trans and when the car is put in park, the parking pin seems to engage, however any ammount of force or incline will cause the car to roll. Any ideas what would cause this?

[1BADAIR]

is the shifter adjusted correctly?

[JoeliusZ28]

yesterday I suggested he make sure the linkage is properly adjusted and today he was still asking me about it so I am *assuming* he has already covered that base. He has also already disconnected everything once and drained/refilled the trans - same result. trans is freshly rebuilt with a 2300 stall but id have to ask him who rebuilt it.

[1BADAIR]

if its adjusted correctly then the guide plate inside is on backwards

[JoeliusZ28]

if its adjusted correctly then the guide plate inside is on backwards

thanks larry. I found another thread describing the same thing. I will forward that along to him.