300-I6 and 35's

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Jul 27, 2003 | 02:18 PM

jeepin_ford

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300-I6 and 35's

I was wondering what gears everyone recommends for a 300-6 w/ 35's? This is going to be a daily driver and it has the NP 4-speed. I was thinking either 4.10's or 4.56's but I didn't know if this low would have the 300 turning to many rpm's at highway speeds. I would like to keep it under 3000rpm's at 65 mph. It currently has 3.08's which are way to high for 35's.

Jul 27, 2003 | 07:12 PM

rustyolred27

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From: North Carolina

300-I6 and 35's

i have an 81 f-150 with the 300 i-6 and the np435 tranny. i have 33" tires and 4.10 gears and i hit right at 3100 rpm on the freeway at 65mph. with 4.10 and 35"ers you should be right on the money as far as freeway rpms go

Jul 27, 2003 | 08:24 PM

jeepin_ford

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300-I6 and 35's

Does anyone know how the 4.10's and 35's are offroad and if the acceleration is close to what it is stock? Or is it better?

Jul 28, 2003 | 10:47 AM

lars915

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From: Northern Colorado

300-I6 and 35's

Don't worry too much about diff gears and off-road performance. Tranny and tcase gearing determine off-road performance. If your diff is geared for acceptable highway performance, it'll be OK off road (unless you want to get extreme.)

I'd be a little worried about spinning an 300at 3100 rpm for any distance. If it were mine I'd be gearing to hit around 2300 to 2500 rpm. The lower gears are great around town or for short trips, but for long distance I'd definitely go with a higher (lower numerically) ratio.

For comparison, I run 4.56 gears and 36 to 37 inch tires. I run about 2800 rpm at 60 to 65 mph (302 engine, but that isn't relevant here). There are many gear vendors online that have calculators to determine tire/ratio/speed/rpm numbers.

Anytime you go with a bigger tire, you will give up some acceleration, even if you compensate with gearing. Rotational mass goes up much faster than diameter. Even if you gear for the bigger diameter numerically, the rotational mass will still slow you down; how much depends on the tire you use.

Jul 28, 2003 | 11:05 AM

Kemicalburns

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300-I6 and 35's

i think the 4.10's would be fine because of the tranny you have is already geared pretty low. and with 35's you should run at aroun 2600rpms at 65.

later

Jul 28, 2003 | 07:09 PM

jeepin_ford

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300-I6 and 35's

I just found out that the lowest gears I can go with without changing the carrier is 3.92. Can someone figure for me what I should be turning at 65 mph?

Jul 29, 2003 | 08:22 AM

Homieonecanoweme

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300-I6 and 35's

I can't remember the formula, but it involves the number of rotations per mile that your tire turns. And a 35" tire will turn right at 600 revolutions per mile.

A little foggy this morning.