Rearend

Asked by Feb 08, 2019 at 10:29 AM about the 1968 Ford F-100

Question type: Maintenance & Repair

Yes i have a Ford f100 truck, rear end
ratio is 3.25 original rear end. Would
anyone know how many teeth would be
on the gear.or do i pull the punkin out?
Sec. i would like to go a 3.00 gear ratio
for around town & freeway.  Any
suggestions

6 Answers

10,815

Ring Gear – 9″ OD – Tooth count 39 – 10 bolt holes – 7/16″-20 RH threads Pinion – 28 spline shaft – Tooth count 12 – 3/4″-20 RH threads

10,815

The difference between a 3.25 and a 3.00 gear ratio is less than 8%. If you have a mechanical problem with the rear, changing the ratio may make sense. If there is nothing wrong with the rear now, getting larger tires may meet your needs and save you some money.

10,815

Here is a good site to compare gear ratios and compare tire sizes. https://tiresize.com/gear-ratio-calculator/

20,690

Count the teeth on the pinion gear and multiply by 3.25 to find the number of teeth on the ring gear. Let's say the pinion is 16 teeth. Then 3.25 X 16 = 52. So your ring gear would/should have 52 teeth. That's just an example how the math goes. But I agree with Gary. Why mess with it? Parts are very expensive too.

180,855

You don't want to go any higher ratio in a pickup. I'm surprised it has that high of a ratio now. My 67 had 3.45s. Remember going higher will reduce the amount of power you have at take off and around town speeds, could even kill the mileage if you went too high.

226,815

Count the teeth on both gears to confirm you really have a 3.25! If you want economy and low gears for towing you should look into a 5 speed conversion in you have a manual transmission or a modern 4 speed auto box with OD if you have an automatic.

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