Pathfinder gear ratio

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pathy-logical
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Pathfinder gear ratio

Postby pathy-logical » Thu Dec 24, 2020 10:40 am

First of all happy holidays to everyone. I hope this finds you all and your families in good health. Prayers and good wishes to those suffering the dreadful affects of covid-19. Please try to keep in mind "this too shall pass".

Have any members changed to 3.36 or higher numeric gears and are still using stock or equivalent 30.5" tires. I'm interested in knowing if there was a noticeable difference in towing ability and how badly fuel mileage was affected.

Thanks.


silverarrow27
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Re: Pathfinder gear ratio

Postby silverarrow27 » Thu Dec 24, 2020 3:29 pm

This might help point you in the right direction:

http://johnmaherracing.com/calculators/ ... alculator/

For me, I'd like to move up to 3.36 myself, but essentially aiming for 4.11 since I work close to home.

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pathy-logical
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Re: Pathfinder gear ratio

Postby pathy-logical » Fri Dec 25, 2020 12:27 am

Thanks for the reply and link but not quite what I was looking for. I'm towing a trailer with a GVWR OF 5500#, TW of 600#, payload of 400#. The PF does okay around Florida because it's so flat but I'd like to start traveling further and will run into hilly country.

I can mount LT235/65-R16C tires which are 28" in diameter. This would effectively give me 3.41 or so gearing, about 9% change, without having to mess with the differential. I think that would be a significant mechanical advantage over the 3.13 I have now. I can then mount my stock 30.5" tires when I'm not towing. My concern is the fuel mileage. I don't want to be stopping every 100 miles to fill up. I kind of have this idea that the mileage might even improve slightly on flat ground because of not having to be so far into the throttle.

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smj999smj
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Re: Pathfinder gear ratio

Postby smj999smj » Fri Dec 25, 2020 8:07 am

On flat ground, it would be better for around town and city driving as far as mileage, but would hurt you on the highway mileage.

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pathy-logical
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Re: Pathfinder gear ratio

Postby pathy-logical » Fri Dec 25, 2020 10:53 am

I understand what your saying but I would have two sets of mounted tires. The smaller set would be used only when towing. I'm not talking 75+ mph driving. So when towing at say 60-65 mph on flat ground the increase in RPMs would be 200 or less and should require less throttle input and minimize torque converter unlock. To me it seems the engine would labor less on grades. I try to maintain a constant speed climbing grades by keeping the engine at or near peak torque no matter the gear or the speed.

silverarrow27
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Re: Pathfinder gear ratio

Postby silverarrow27 » Fri Dec 25, 2020 11:42 am

Correct, theoretically the engine would labor less as the rpm range with higher gear ratios whether via smaller tires, ring & pinion, or transmission gear changes as it'll be nearer to the peak torque. Peak tq on the VQ40 is at 4000 rpm though so you will have to give it some gas on the uphill, but not as much, and it may actually be healthier for your engine to run a higher RPM when towing anyway so it's not lugging. As you said, fuel usage will be dependent on terrain and hills. Your Pathy will most likely guzzle more fuel on flat land due to higher rpms, but will guzzle less on hills. It's a trade off or compromise.

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pathy-logical
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Re: Pathfinder gear ratio

Postby pathy-logical » Fri Dec 25, 2020 11:03 pm

Thanks for the replies.

So does anyone have any real world experience with this theory? My biggest concern with this idea is running out of fuel because the tank is so small.

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smj999smj
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Re: Pathfinder gear ratio

Postby smj999smj » Sun Dec 27, 2020 5:29 am

Just something to throw in to the discussion: if you are going to be swapping tire sizes, remember you should also change out the spare tire, as well. If you have a flat and need to replace a wheel with the spare of a different size, it's going to make the traction control system kick in. I found this out when a friend had two tires replaced and they put the wrong size tires on the two wheels (265/70 vs 265/65).

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pathy-logical
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Re: Pathfinder gear ratio

Postby pathy-logical » Sun Dec 27, 2020 9:15 am

Thanks for pointing that out. I'll definitely keep that in mind.


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