my automatic transmission seems to work ok when i'm driving, but it doesn't hold the truck in gear when i'm in park. you know how normally a truck won't roll if you put the trans in park or in gear? this one still rolls as if was in neutral. i have to put the parking brake on. any idea why it might be doing this, and how i can fix it? it's a '78 f-150 with a 302 and c4.

 

have you checked the linkage adjustment? If it's in adjustment then I'd say your in for tranny work

 

i have a '78 f-150 with a 302 and a c4. the trans seems to work ok when i'm driving down the road, but when i put it in park, it doesn't lock the truck in gear like normal. the truck still rolls even when it's in park or in any of the gears, just as if it was in neutral. any ideas what this could be, or how to fix it?

 

Hi, Sounds like the locking pin got broken off. If you are moving and put it in park it will do this. I think you have to tear it down to fix it but not sure. Erv

 

Slop in the linkage / linkage adjustment (as previously mentioned). It could also be a result of a broken/defective parking pawl inside the tranny.

 

In 78 there was a recall on this part.

My truck popped into reverse in Oct 2005 and it cost me $1290.00 to fix a Ford salesmans car parked on the side street in front of the dealership here in town.
long story surrounding event

 

The Parking pawl pivots on pin and the tension is maintained by a small wire spring. The pawl and the pin are very strong, so I would guess that the tensioning spring broke. The tail housing and govenor assmbly will have to be removed in order to get to the spring I believe.