I have a 87 F150 4.9L with NP435 transmission. This gets horrible gas mileage due to the low gearing.

I am wondering what all is involved in swapping to the Mazda M5OD-R2 5 speed. I no longer tow anything with the truck other than a small trailer and riding mower so I don't need the extra umph of the 4 speed granny low.

Any thoughts?
Thanks,
GaryC

 

The gearing isn't the reason for the low MPG - it's driving style, engine condition, maintenance, and the thirsty nature of the 4.9L. You'll never get it above ~16mpg no matter what, so either get used to it, or get something smaller. Read the results pages of Project MPG, and this caption:

 

Well, Steve 83 has a nice collection of pics, and is somewhat of a monday morning quarterback, however the answer to your question is...yes, you can put an M50D in your truck. You will have to buy the clutch master cylinder line that goes from the master to the slave(for a truck with the M5OD from the factory). You have an external slave and the M5OD has an internal. You may need to also get a new trans crossmember and driveshaft due to the extra length of the OD trans. Oh, make sure you get all parts from a fullsize Ford truck. Doesn't matter what engine, all fullsize M5OD trannies have the same bellhousing bolt pattern.

 

Except for the 4.6. Look for one from a 4.2, 4.9, or 5.0.

 

My bad, I didn't specify years. Up till 96, all fullsize are the same bellhousing.