Rear end gears

[tanman722001]

Hi guy,I was wondering if 3.54 gears would help my gas mileage any of make it worse.I have 4.10's know.I have a 400 with a C6 trans.As of right know running 33x12.50's tires.Thanks Tony

 

[fatherdoug]

With 33's, I would stay with the 4.10's. The taller tire has effectively reduced your axle ratio to a 3.8. A 3.50 ratio would actually be a 3.20 with the 33" tires. I wish that Ford would have used a 3.73 in the earlier light trucks.

 

[LEB Ben]

I'd say it would help a tops of maybe .5mpg at hwy speeds...otherwise you'll never see a difference. As Doug pointed out, your truck already has a lower effective ratio, you drop it any more and your foot will be through the floor trying to get you to move and that 400 will be sucking more gas.

 

[tanman722001]

Would it be the same if I go down to a 265/75R16 Tire?

 

[fatherdoug]

A 265/75/16 would be between 31" and 32" tall(31.6"), which would give a slight improvement in the axle ratio(closer to a 4.10). But like Ben said, mileage improvement would be negligible. We're talking about a brick-shaped vehicle.

 

[tanman722001]

ok thats for the info guys

 

[BuzzGun79]

FYI Speaking very truthfully my 79 F250 4x4 has the 3:54 gears,and 39" x12.50x16.5 mudders with the stock 460/Beefed up C-6 i am getting 12mpg's consistantly.Grant it i have cubic inches in my favor to move the vehicle.In all Honesty tho,the truck takes off fom a dead stop quickly and impressively without a great deal of throttle input.at highway speeds she's taching 2200 rpm's and has plenty of passing power should i need it.for a heavy lifted rig,I cannot complain with 12 mpg.most peeps told me i would be lucky to see 7-10 mpg's generally speaking.

 

[tanman722001]

ok thats for the input.