Hello,

Just wondering what gears the 400 /C6 would have in a half ton from the factory. I have a 72 with a 400/c6 and it has 3.70 gears. It had a 302 c4 in it.
What gears would give me good mileage and not be a dog. Its mostly a cruiser/ summer time truck.

Thanks Pat.

 

A 3.50 gear is a good compromise between acceleration and mpg. Decent to tow with too.

If you don't tow or plan on towing, I would even consider 3.25 gears.

.

 

3.50 is what most came with. 400 has plenty of low end so they work well

 

Agree around 3.50 would work well as an all around gear with the 400. Also it depends on tire diameter and usage. If you are stock or a just a bit bigger in tire size around 3.50 should allow her to cruise up to 70 or so and have decent acceleration and moderate towing capability. If you are running taller tires... say 30"+ the 3.70 should be fine. If highway driving is not a priority, I'm not sure changing the 3.70 is worth it. With smaller tires, more highway use and limited towing 3.25 would be best though acceleration would suffer.

 

Good mileage with a 400/C6 in a 72 F100 is going to be relative. As compared to a F250 4x4 yours will get relatively good mileage, compare it to a thirty year newer truck and its not so good.

Just for driving, the 3.25 wouldn't be bad.

You could even set up two different gear sets for your nine inch, less than an hour and you can swap them out. Don't forget to refill with gear oil.

Robert