Ring and pinion Gear sets question

Ring & Pinion Gears for V6 Frontier & Xterra
Application Part # Price

The following are the four gear sets availiable for the Xterra/frontier through SLR. Does anyone know exactly what percentage lower it is from factory for these at both high and low range. And if your really a math wizzz, come up with the new crawl ratio. I would appriciate it.

4.265 D162 $475.00 set

4.875 D163 $475.00 set

5.143 D164 $475.00 set

5.429 D165 $475.00 set

The factory axle ratios are as follows:

non limited slip 4.363
limited slip 4.636

Here are the "percentages of change" for the final drive if you were to change:

from 4.363 to:
4.265_______+2.298%
4.875______-10.502%
5.143______-15.166%
5.429______-19.635%

from 4.636 to:
4.265_______+8.699%
4.875_______-4.903%
5.143_______-9.858%
5.429______-14.607%

[ 01-25-2002: Message edited by: John Doe ]

Well shit, thanks man. You either got a calculator that can convert shit like that, or its just that Tennessee wisdom (Im from NE Tenn. originally). Appriciate it...

Ok but what do those numbers mean?

A higher numerical gear translates to lower gearing.

With the stock 4.636 gearing, the driveshaft turns 4.636 times for each roatation of the axle.

Changing the gearing to 5.143 would lower the gear ratio. The axle would have to turn 5.143 times to rotate the axle once.

Bigger tires need lower gearing to turn them at the same RPM to achieve the same speed.

what affect would changing to 5.143 gears have for your on road acceleration or top speed? does this also affect the speedo? does anyone know of a chart that tells the recommended gears for particular tire sizes?
Is it true that you have to use the same gearing for the front and rear diffs?

[ 01-27-2002: Message edited by: Ag_xterra ]

with bigger tires, it just sort of cancels out, unless you got the 4.636/5.429 x new tire diameter/stock tire diameter x 100 = % of speedometer variation.

I think.... I tried reversing it and it seems right this way...

32.7/29.5 = 1.051
4.636/5.429 = 0.854

1.051 (difference in tire size (increase in distance traveled per revolution)

0.854 (reduction of tire revolutions)

1.051 x .854 = 0.8974 reduction in tire revolution over stock gearing and tire size.

this is with 31 inch tires.

with 32.7 inch tires (about the biggest I have seen on an Xterra) it is .9466 or 94.66% of the original gearing. Not a huge difference. but a difference compared to the 110% that the 32.7" tires gives you.

This is making my brain hurt. you put the bigger tires on, and your speedometer slows down, but your crawl ratio goes up, meaning, you go farther for every revoution of the engine. With the gearing change, you effectively get to use bigger tires, and a 5%-11% reduction in gearing. 31" tires are a good thing in this instance. they allow you to crawl slower.

There really isn't a recommended chart for recommended gearing because the ring and pinion isn't the only thing to consider.

Transmission gearing, transfer case gearing, and the power curve of the engine need to be considered.

The entire goal of regearing is to get the engine RPM back to stock after increasing tire size.

Gear too low, and the engine redlines too soon, and you lose top end. Gear too high, and the engine lugs at cruising speeds.

Acceleration will never be the same because you are turning bigger, heavier rubber, with a higher coefficient of friction.

The trick is finding that sweet spot in the RPM curve that offers the most drivability.

I'm bringing up a really old topic, but its the only one I found with ring and pinion explanations. Since the new Calmini crawler gears are out, I have some questions.

If I were planning on getting a new R&P and the crawler gears, should I get the crawlers first in order to determine the new R&P ratio? Or would it matter, I have no idea. There is only 1 gear ratio on Calmini's gears correct?

-Tim

Get the t-case gears, they make a MUCH bigger difference. If you swap the R&P, you'll be messing with your highway power/RPM/mileage too, and you probably don't want to do that. The t-case gears will make plenty of difference and you'll forget about the R&P gears the first time you use 'em.

Brent

I was told by AC that the 5.14 gears will correct the speed-o with 34in. tires. That will work great for anyone using 33in or tall 32in tires. The transfercase gears will only affect 4-low and not help with normal onroad driving with bigger tires.
If you wheel a lot then go with the transfercase gears (your clutch will thank you). If you run huge tires but don't see 4-low to much then go with the differental regearing.

Won't you need to change the front diff R&P as well?

So let me get this straight:

The crawler gears will only affect 4-Lo performance? So if I have 33" tires, my highway speed/fuel economy will remain unchanged with the calmini gears? Whereas if I get the new R&P (front and rear), my highway performance will be better with 33" tires, but my crawling speed won't be as low as with the calmini gears? How big of a difference are we talking in 4Lo between the two options? Any idea how much lower the gearing would be with the R&P over stock (with 33" tires)?
This is an email from AC regarding their R&P for anyone who is interested:

Freaking huge...

Crawl Ratios
============
Stock 4.636 R&P and stock T-Case 33.53
D165 5.429 R&P and stock T-Case 39.26
Stock 4.636 R&P and CALMINI T-Case 65.06

This is all covered here with the calculators.

Consider your top speed in 4lo in 5th gear...

Cut that in half with the new tcase gears. I wont be going very fast in 4 lo, but I will be able to climb things very sloooooooowly in 4lo.

Friday is at hand. Gears will be in hand next week. Then to install.....

Todd

Really? I must have missed the option for the 5.429 axle ratio. Since I don't know the formula, I had to ask. Thanks for pointing that page out though.

The calculator pages were designed for components and options most people would have, not for custom ring and pinion sets. I only added the 4.9:1 axle and CALMINI transfer case ratios a few months ago.

Simply put, crawl ratio is (axle ratio X transfer case ratio X your lowest gear).