gear ratios

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Sep 1, 2010 | 06:44 AM

dtaylorlc

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gear ratios

I have a 2002 F-150 2wd with the 4.2 v6. I just put new tires on and moved up a size to 265/75-16. I love the tires and the look but my rear gears are going to have to go. I currently have 3:31 and going 75mph I run about 2000 rpm, no bottom end. I'm looking to see if anyone has anything similar or any advice.

Thanks
David

Sep 1, 2010 | 07:45 AM

Johnny Langton

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From: SE Texas

Quote:

Originally Posted by dtaylorlc

With a 4.2L,you need a 4.10 or more, IMO. That engine doesn't make enough torque down low to keep the vehicle moving at speed, and the extra torque multiplication will make driving altogether a much better experience. You'll likely see no loss or possibly even a gain in fuel economy as well since the engine will not see as much load.
JL

Sep 1, 2010 | 01:24 PM

dtaylorlc

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I have been considering 4:10's but I don't want to run too many rpm going down the highway. This is my primary vehicle so I don't want to go to much on the rear end, I'm not sure how the 4:10's will do when traveling.

david

Sep 1, 2010 | 01:30 PM

Johnny Langton

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Quote:

Originally Posted by dtaylorlc

You're gonna turn approx 800 more rpm's than with the stock gearset. You'll honestly see little or no loss of MPG because the engine will be under less load and will consume less fuel .
JL

Sep 1, 2010 | 04:15 PM

redwood

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From: Pelahatchie, MS

I agree with Johnny on this one. If you really, really feel like a 4.10 is too much, I wouldn't go any further south than a 3.73.......

Here's a gear ratio to tire size chart. It puts you right where you need to be with a 4.10:
Differential Gear Ratio Chart - Tire Size to Gear Ratio

Here's a tire size conversion chart from metric size to inches:
Tire Size Calculating Form