I know there are a pretty sharp bunch of guys on this site. Sure you guys can give me good answer. A buddy of mine has a 99 F450 7.3 rollback with 4:88 gears. At 65 to 70 mph she is clocking around 2700 rpm. She burns some serious fuel at that rpm. Sometimes we get into running up a short grade here in the mtns. What would we lose if we say went with a 3:73 ratio? BTW it is a manual 6 speed trans. Thanks

Smokie

 

check this out
Automotive Calculators offer to you by Ford Trucks Enthusiasts | www.ford-trucks.com

 

Do you know if your F-450 has a Dana 80 or a Dana 110?

 

It has a Dana 80 !!


Smokie

 

I did the same gear swap on my 2008 F450. I haul a camper and tow a 7000 pound trailer, I didn't need the lower gears.

 

F250 Wheels ! How did the truck run down the road with a load ? Did you have enough power to climb the hills? What kind of rpm were you running at say 70 mph? Did your mileage inprove any? This truck was I think mostly for town use and has a small 16 gal. tank. We use it to haul cars from auctions and they are all about 1 1/2 hours or more away. It seems we are always at the pump!! It is either better mileage or a bigger tank!!! Thanks


Smokie

 

It runs down the road fine, I allso have the 6.4. how good it runs depends on how you load it. I was getting 9MPG empty, after gear change I get 13 MPG. At 70 MPH I was at about 2650 RPM, now about 2000. I still plan on removing the stock 38 gal. tank and installing a 62 gal. tank.

 

F250 Wheels! Thanks for the input. One guy told my buddy that a gear change would just kill the truck!! The only thing I think will hurt is maybe aceleration. It is only a 7.3 but to me my 7.3 with 3.73 gears can haul my fiver with no trouble! Granted it has to work some but that is why you buy a dezzel in the first place. They are workahaulics !!!



Smokie

 

3.73 is too tall for a F450. a 4.10 swap should net about 14-15 mpg at 65, empty or lightly loaded. 4.30 will get about 13-14 at 65.

 

I was going to say, my dad has an '08 F450 4x4 with the 4.33's, and at 65mph he is putting down about 13-14 average. He hauls a 3700 lb truck camper or a 14,000 lb fifth wheel, and with either of those tied in the bed he pulls about 9 mpg. He recently made a trip through Pennsylvania on US30 and had no troubles pulling that fifth wheel through the mountains.

I don't think I'd want to go down to 3.73's from 4.88's. I would hit the 4.33's and try those first.

Also remember, if this is a 4x4, you will have to swap BOTH SETS of gears, not just the rears.

 

Thanks guys for your replys! I was mistaken on the gearing plugged in the vin and it looks like it has a 4.59 no posi. this truck is also a 2wd unit. With 19.5 rear tires and 6 speed manual trans.


Smokie

 

If you want to get accurate rpm at ??mph calculations you will need to know the tire diameter. The wheel diameter doesn't mean anything as far as calculations are concerned. IMO 4.30s would probably be a better bet. Keep in mind the 6.4l in the newer trucks is a whole different beast than the old 7.3l. If the truck has never had the gears changed there should be a tag on the axle diff cover that tells you the gear ratio, thats if its still readable. I never heard of Ford putting 4.59s in anything, for the chassis cabs 4.88s were the norm.

 

I believe 4.88 was the only gear for a 99 F450. Later years were offered with a 4.30 option.

 

I am going to put the vin number in here maybe you fellas may have a better site to check than I did! Maybe you can get something from it? Thanks

vin 1FDXF46FXXEA61011

Smokie

 

There's nothing in the vin for axle ratio. There is a tag when you drivers open the door that will give the factory code. It will be on the axle tag too.