I have a 99 F250 SD crewcab 4x4 diesel with 295/75r/16 tires. I want to change to 4:30 gears to get more power out of the truck. Somebody in the forum had told me that a 35 would bring me back to stock with these tires. I pull a 24' Haulmark enclosed trailer that is loaded. I have always thought that the truck should have had 4:10 gears in from the start but I could not order it that way. I do have a Banks kit on this truck but that still does not pull this trailer as well as I would like.
I only do about 13 mpg in town and approximately 9 mpg on the highway pulling this trailer so I can't believe that it will do any worse. I do uasually drive between 70 to 75 with the trailer.
What are the pros and cons of using the 4:30 gears??????
Thanks,
Kevin
kstones63
99 F250 SD CC Deisel
29 Ford Model A Sedan Delivery
95 F350 Flatbed dually deisel
63 F100 project

 

According to the following from the BFG page http://www.bfgoodrichtires.com/specs...t-a-ko/44.htmlyour 295 is only .2 inches taller than a 305 33.2" and 33" respectively. running either of those tire with stock 3.73 gears = out to about a 3.55 ratio. If you go up to a 4.10 gear set with the 295's or the 305's then you will = out to about a 3.73 final. If you jump up to the 4.30 gears then you will be running about a 4.06 ratio( wich is close enough to the 4.10 that you originally wanted.)
If your truck is just for towing then go for it, but if it is your daily driver then I would say your mileage will get worse.

 

Very well said bdrummonds. I've tried to add to your reputation but, it won't let me.

 

Back when I was a kid I put 4.33's in a car for street driving only (racing) and daily driver. I put up with it for about a month. In fact I drove it to California from New York and back. The first thing I did when I got home was go back to the 3.90's. Does that answer your question?

 

Real quick for the new guy. How do I find out what my gearing ratio is?

 

Well, if you don't have a dually, I can almost guarantee you have 3.73's.

 

No dually. Late 99. Crew. 4X4 Long Bed. I bought the truck with 315/75/16 tires. They seem too big but good tread left. Is that a bad set up with the gear ratio?

 

Two options, New gear set for both ends or US Gear underdrive so you can have the low gears for pulling and the tall gears for cruizin. I have a 550 with 4:88 gears. love it for pullin,but not for cruizin,so.... the US Gear overdrive should be here next week. its about a push money wise and you get more options. Barney

 

Well on a F450 with 4:30 gears the rpm will be at 2500 RPM at 75 Mph.
But I don't know how tall the tires are?
I'll go look for you Hold on__--____---- There are 32" tall 225/70.19.5

2500 Rpm is ok for a 6.0 but a 7.3 there allmost out of breath.

 

If it works for you, why change it? You will have less power when pulling, so if you pull heavy often enough it may be worth regearing or installing smaller tires. If not, and it works for ya, don't worry about it.

 

My truck is not driven much (45,000 miles on a 99). It is used mostly for pulling the trailer. I have a 3500 mile trip coming up and I don't want to be sorry either way. One week in Sturgis, then off to Idaho to do a job up there and then a few days of riding Harleys in Canada in August (beats the Phoenix heat).
My 95 flatbed dually diesel has 4:10 gears in it and does a constant 13 mpg and it weighs 10,000 lbs before any material is put on it. That is why I am thinking about the 4:30 in the 99.
Thanks,
Kevin
kstones63

 

I think with your size tires you would be happy with the 4.10 set, that is what will put you back as close to stock as possible, and these things pull pretty darn good with stock gears.

 

TNT, I don't think you actually got an answer. To find out what your gears are, there is a metal Tab on the rear Diff that will show 3 73, and there is a sticker on the front axle if i recall correctly, or you could use your V.I.N. as well. I personally would like to have 4.10's with my 35" I have 3.73's and it's not as quick off the line as it should be (even for an 8000# truck)and 4.30's would make it run like stock but i believe fuel economy would be better with 4.10's Sorry for long winded post