I have a 1990 F-150 with 65K miles on her. I am the second owner of the truck. About a month after I bought the truck the throttle body started sticking to the point where it became dangerous to drive. Changing the throttle body with a new one cured that problem. However, a transmission problem continues to plague me.

The transmission intermittently shifts hard when going into overdrive. This occurs especially in traffic and where speeds bounce back and forth between 40 to 50 mph, and also where I find myself in Drive for a long period of time before I reach the 45 MPH shift point. Under load, such as getting onto the expressway and continually accelerating, the transmission shifts fine. However, if I am not accelerating hard, the transmission feels as if it is winding up and then slams into OD. Downshifting is smooth from all gears.

A friend mentioned to me that leaving the tranny in Drive while in traffic may be the best solution. I have tried this, but the tranny still shifts hard into OD even when I manually go from Drive to OD. I've had the tranny serviced by Ford, but the hard shifting problem still persist. Any help?

By the way, the previous owner might have been towing a somewhat heavy load (horse trailer?), as the truck is outfitted with a "Jake-Brake." I don't know if this would have any bearing on the problem.

Also, the tranny does seem to shift better when there some weight in the bed.

 

Jake brakes are something you only find on diesel engines. It is a exhaust actuated braking system that holds engine enhaust back from leaving and uses engine compression to slow the vehicle. Your gass F150 will not have this. Unless for some crazy reason there was a diesel conversion done to your truck. As for the tranny, could be electrical if it's the E40D.

 

You are correct. Perhaps, I used the wrong terminology. I should have said "electrical brake actuator" in lieu of "Jake-brake." I have been playing a bit since my inquiry and found that I can control the OD shifting better manually; shifting into OD when speed indicates around 50-55. I also found out that if I have to back off of the throttle (with the transmission in OD) before the 45 mph shift point is when the tranny slams into OD. Maybe it's getting mixed signals? So, and in the meantime, I have opted to manually shift into OD, since most of my driving is in city traffic. Besides, the exhaust rumble really sound good when I'm not in OD and the motor is de-celerating (I'm running a 40 series FlowMaster, K&N filters, and Tornado intake). Thanks for the help. I'll get things checked out shortly.

 

You say you are the second owner? Did the previous owner put any sort or shift module (a chip, or tranny kit) in it? I have the Banks trans-command for my truck and it really slams through the gears when I get on it hard.

 

Not that I know of. What would I look for?