Interesting...

The 2003 SE Xterra with manual transmission gets a 4.90:1 ring and pinion, up from the 4.636:1.

I want them.

Sourced from www.nissannews.com

Maybe if you ask Nissan politely they will give them to you.

I didn't find the news article. Was there a stated effect on torque??

Wouldn't you need to swap tranny gears as well if you wanted to keep the RPMs low at highway speed? Or, would your 32" tires make up for this change?

Look in the product listings for the 2003 Xterra, it's in the specs.

It can't affect torque, since published torque values are measured at the engine. You should feel it on the street though.

I assume they did it to match the tire size better.

Gottcha. I was thinking increased leverage at the wheel, but, actually this will increase the number of turns of the wheel to the engine rpm. Should see increased gas milage. I found the link. thanks.

Actually, the other way around.
Torque will increase at the wheels, just like it increases when in 4Lo.
The engine will be turning more too, 4.90 times per revolution of the wheels as compared to 4.636.

City mileage should increase (easier acceleration), highway mileage should drop (higher RPMs).

http://www.nissannews.com/nissan/2003vehicles/xterra/specs.shtml

Interesting,
Brent

So.. did they have to do something to the front diff as well so the front tires turn the same amount when in 4wd? Does the front driveshaft turn the same revs as the rear driveshaft?

Nissan fits a front diff with exactly the same ratio as the rear.

The V6 models of the XTerra are fitted with the 33 spline version of the H233B differentials in the rear. These diffs are available in only two ratios - named "4.636" and "4.900". The pinions in both cases are 8 tooth ones (obviously not the same pitch), while the ring gears have either 37 or 39 teeth. (The astute mathematicians among us will note that this works out to ratios of 4.625 and 4.875 respectively).

Nissan has then had fun assigning these two ratios across the V6 range.

To find out what axle is fitted to your vehicle, just look on the driver's door frame. There you'll find a beige sticker with tire pressures, the VIN and other such details. In the lower left corner is the heading "AXLE", and under it you'll see either "HG46" or "HG49", which means the rear differential is an H233B type of either 4.636 or 4.900 ratio.

As far as fitment to the vehicles themselves is concerned, the general pattern is :

15" rims -> 4.636
16" rims -> 4.900
17" rims -> 4.636 (on the SE S/C models)

To put it another way,

An XE will have a 4.636
If it has the optional LSD, it will have a 4.900
An SE will have a 4.900, unless it has 17" rims and an LSD, in which case it'll have a 4.636 diff...

There are exceptions. For example, the short-lived 2002 5-speed XE S/C has 4.636 diffs and 16" rims...

In all cases, the front diff will be the R200A.

If you wanted to change axles and tire sizes, you'd need to change both the front and the rear diffs, as well as the speedometer encoder gear in the transfer case to keep everything "accurate".

[In case anyone really wants to know, the diff type numbers are the diameter of the ring gear in millimeters - 200mm for the front and 233mm for the rear in the case of the XTerra.]

Regards,
Richard.

what axle code or vin number would correspond to the LSD rear?

The numbers on the door frame sticker don't tell the lay person anything about the axles. (Someone at Nissan Consumer Affairs would be able to look up the original build details, given the VIN.)

The window sticker would say if it had the LSD, if you have access to that.

One direct way to tell is to look for the sticker on the diff casing telling the serviceman to use "LSD Oil Only", but that may be long gone...

An indirect way would be to jack up (and support the vehicle on a stand!) one rear wheel. With the transmission in neutral and the parking brake off, judge how much resistance you feel while turning the raised wheel. Without an LSD, it should spin very freely.

The only absolute way would be to remove the third member and look...

Regards,
Richard.

FYI, had a look at a 2003 SE this afternoon, and sure enough it said HG49 on the door jamb sticker!

Brent