Transfer case rattle

[AllTheTimeInTheWorld]

I have a 2001 QX4 with a rattle that is bothering me primarily because I'm not sure what it is. Usually it's really noticeable when you first take off in the morning and quiets down significantly the rest of the day. It rattles loudly when accelerating from a stop and quiets down at higher RPMs. As it shifts to second you can hear it again until you get to higher RPMs again. At first I thought it was an exhaust shield coming loose, but after pushing, pulling and tapping around under the car I've found nothing loose. Then I thought it may be in the transmission (sound seems to be in that area) so I dropped the pan and changed the filter and fluid (fluid was dark, but no burned smell); no change. Last night I drained the transfer case (fluid was black but didn't smell burned). I drained about 3 quarts out, but only got about two quarts back in. This morning I took it out for a drive and the rattle was noticeably worse. Two things: 1. I checked the case fluid level when I got this car and the level was good (wish I'd changed the fluid then given how dirty it was). How is it I got three quarts out and can only get two back in? Are there two service plugs? The car was sitting level in my garage. 2. Does anyone have any ideas about the rattle? Thanks.

[Towncivilian]

Grease the driveshafts (any NLGI No. 2 lithium soap base grease with molybdenum disulphide) and check (or change if you haven't in a while) the differential fluids.

The transfer case only has a drain and fill plug. Not sure why you only got two quarts back in; the capacity is 3.17 quarts assuming you've got auto-mode 4WD.

[AllTheTimeInTheWorld]

It is an auto-mode system. On the way home this afternoon I got off on one of our Iowa rock roads and shifted the case through all modes to maybe help flush the case out and am about to go check and drain it again (see if it went down and be more careful of how much drains out). I changed the diff grease front and rear with a good 75W-90 synthetic, but never have seen the zerks on the shafts. I'll look again, maybe broken off. I got this car last August and have been slowly trying to work the bugs out of it; I really appreciate your help.

[Towncivilian]

Naturally they rotate with the driveshaft, so if you can't find it move the vehicle a couple feet and hopefully they'll be visible and accessible.

What brand of ATF are you using in the transfer case? What brand of gear oil did you use for the differentials?

[AllTheTimeInTheWorld]

Found it. The transfer case still has me though. The drain is in front under the drive shaft and the fill I found is on back on the outside left (driver side). Looking at the FSM it should be between the filter and rear drive shaft. Speaking of filters, have you changed these? from the looks of this fluid, even the second batch, I'm thinking I should. I'll go look again for a higher fill plug.

[Towncivilian]

I really have no idea, my Pathfinder is 2WD and I've never serviced a 4WD Pathfinder or QX4's transfer case or front differential. Which filters are you talking about? Do you mean the transmission pan strainer?

[AllTheTimeInTheWorld]

No, it has it's own filter according to the FSM page TF-116. The bottom picture on page TF-115 shows the fill plug I've been messing with (not marked, but appears to have a line running to it), just bellow the transfer motor and left of the oil filter. For the life of me I can't workout why it only took two quarts or so. I've been looking at motor mounts and shocks, anything that would change the angle of the transfer case on level ground. Weird huh?

[Towncivilian]

Huh, I wasn't aware the auto system had a filter. I'm not aware of anybody ever having replaced the filter, either. The filter is stupidly expensive at $115 for a new OEM one, and I'm almost certain no aftermarket option is available. There's definitely a magnet inside the transfer case somewhere, but I'm not sure if it's even viable to remove the transfer case cover to clean the internals & magnet with brake cleaner.

I would run the cheapest Dexron III fluid for a few thousand miles and drain to "flush" the transfer case out somewhat; do this a few times, then fill with Nissan Matic D.

I'm also clueless as to why your transfer case capacity is not the stated 3.17 quarts. That's very puzzling.

[AllTheTimeInTheWorld]

Silly me, it wasn't the transfer case. I had my wife start the car and gun the engine while I crawled around the car and found it was (drum roll please) the right resonator. What a shame guess this means I'll have to change the exhaust. Time for an upgrade!