Bigger Gears?
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Joined: Jan 2003
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From: Still under the hood in O
"Bigger" gears, as in higher numerically WILL increase the operating RPMs. If your truck is heavy (4x4 with taller tires) with the little 302, it may actually increase mileage by letting the motor run in it's powerband...ie..it won't have to work as hard.
If it's just a 2wd with either motor and stock or shorter than stock tires.......yes it will drink the gas.
If it's just a 2wd with either motor and stock or shorter than stock tires.......yes it will drink the gas.
Post Fiend
Joined: Nov 2001
Posts: 14,947
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From: Topsfield, MA
The 35" tires will require a gear change to a gear ratio that is higher than stock. You'll have to change both gear-sets front and rear...something that should of been looked into when putting the 35s on. Any time you change the tire diameter that much, you need to adjust the gearing to compensate. It'll bring back a lot of power and gas mileage for you. Depending on what transmission you have, you may want to go up to either a 4.10 ratio or a 4.56 ratio. Some may say 4.88 but it all depends on what you want your RPMs to be at on the highway. Most likely, your stock ratio is 3.55, but it should be checked.
Senior User
Joined: Dec 2004
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From: Duncan,OK
My buddys put 30" tires on his bowtie with 3.42s his mileage droped to 11mpg.
Last year I installed a locker and 3.73s he gained almost 5mpg bringing it up to 16mpg.
With new R&P and bearings cost in my area about 450.00-500.00 each if you have it done. A lot cheaper if you can do it your self.
Last year I installed a locker and 3.73s he gained almost 5mpg bringing it up to 16mpg.
With new R&P and bearings cost in my area about 450.00-500.00 each if you have it done. A lot cheaper if you can do it your self.
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Post Fiend
Joined: Nov 2001
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From: Topsfield, MA
It's about $600 in parts maybe alil more....Lots of labor at $65/hr....i'd say for an F-250 it would be around a $1200 job to pay a shop. It's tricky for the first timer, and not to be rude but to be honest if you didn't know you need to change gears for a larger tire, than you shouldn't be trying to do axle work.
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Post Fiend
Joined: Mar 2005
Posts: 8,542
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From: Louisiana
Originally Posted by j250hd
Its A 5 Speed Manual. Does That Make A Difference? How Much Is The Cost To Replace Them?
With your 35" tires, you need new gears, your old gears are running your RPM's higher than they should, which is why your truck is sucking down gas.
Good luck,
-Matt
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From: Still under the hood in O
Originally Posted by MBBFord
With your 35" tires, you need new gears, your old gears are running your RPM's higher than they should, which is why your truck is sucking down gas.
Post Fiend
Joined: Nov 2001
Posts: 14,947
Likes: 6
From: Topsfield, MA
Originally Posted by MBBFord
It depends if you want to put lockers too. You will need to put 4.10s, or maybe 4.56s gears. They cost about $150 per each ring and pinion. With a install kit of around $50 each. Lockers will cost anywhere from $300-700. Labor is anything but cheap, the best place I found charges $50 an hour, for 6 hours of labor per axel.
With your 35" tires, you need new gears, your old gears are running your RPM's higher than they should, which is why your truck is sucking down gas.
Good luck,
-Matt
With your 35" tires, you need new gears, your old gears are running your RPM's higher than they should, which is why your truck is sucking down gas.
Good luck,
-Matt
The gears are $200+ each, the install kits are $150-$180....etc...those heavy axles are wicked expensive. I've spent the last month tracking down cheaper parts for the rear axle in my F-250.
Thread Starter
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Senior User
Joined: Oct 2004
Posts: 235
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Was Wondering If The 4.10's Will Keep Me Fromgetting Better Gas Milage On The Freeway At Around 80mph? If So Is There Something In Between The 4.10's And 3.73's That Would Work? I Don't Pull Or 4 Wheel Much Just Want A Little Better Go On The Bottom End And For My Engine Not To Have To Work So Hard.