My 1999 diff is making noise and I have been looking at the salvage lots for a replacement. Mine is a 2wd 5spd. The firewall has HG46 which I have read means it is - HG46 meaning H233B w/ 4.625 to 1. It appears from cross referencing that 1996-2004 would work in my truck. I know that 4wd pathfinders need to be concerned with gear ratios matching front and rear.

As a 2wd do in need to be concerned that I get the exact same gear ratio?

From my reading on the issue, it appears that the automatic Pathfinders the of the same age came with the HG46 also.

So is there any issue swapping out a HG46 from an automatic to my manual HG46?

Thanks for the help.

If you have 2WD, then the gear ratio doesn't matter as much as it would in a 4WD. A different ratio would affect your speedometer and odometer readings, gas mileage and acceleration to some degree, but that's it. Be aware that there are open and LSD versions of the H233B rear. Many Hardbody trucks used the H233B rear end, as well. I know there was a change in the spline count of the axle shafts at some point, but I'm not exactly sure what year. I know some are 31 spline...I "think" the other is 28 spline, but I'm getting old and my memory isn't as sharp as it used to be! Car-part.com is a good site for locating used parts.

smj999smj wrote:If you have 2WD, then the gear ratio doesn't matter as much as it would in a 4WD. A different ratio would affect your speedometer and odometer readings, gas mileage and acceleration to some degree, but that's it. Be aware that there are open and LSD versions of the H233B rear. Many Hardbody trucks used the H233B rear end, as well. I know there was a change in the spline count of the axle shafts at some point, but I'm not exactly sure what year. I know some are 31 spline...I "think" the other is 28 spline, but I'm getting old and my memory isn't as sharp as it used to be! Car-part.com is a good site for locating used parts.

Thanks for the fast reply. If I didn't think the spline count would matter if I did a whole axle/diff swap? I just want to make sure I don't have anything to be concerned about it bolting up?

If you are replacing the entire axle, then you don't have to be concerned about spline count.

If you really suspect the diff needs replacing, get another HG46 rear diff from any 1996-02 Pathfinder (HG46 didn't exist for 03-04) or 00-04 Frontier/Xterra. Any transmission, any drive. You can get a LSD diff with the 4.636 gears for a nearly-free upgrade.

The models above all have 4.636 (51:11) HG46's. Older HG46's have 4.625 (37:8). It's a trivial difference numerically, but all those diffs have 31-spline side gears. The models above are 33-spline. You can use the 4.625 gears, but it'll require disassembling both diffs to swap parts around and set up the gears properly.

I wouldn't bother swap axles...more work, more cost, no benefit unless your axle is damaged.

In terms of repairing what you've got...changing diff/pinion bearings requires special tools. There are adjustment rings on the diff for setting backlash...pretty simple with the right tools, but can't address bad bearings, of course.

Swapping diffs is a DIY thing. Undo/loosen some brake lines, remove some nuts, slide the axle shafts out, disconnect the driveshaft, remove more nuts, lift diff chunk out, reverse.