Towncivilian

Pick your year from http://www.nicoclub.com/FSM/Pathfinder/

This is a 1989 D21 manual, which should be close enough: http://www.nicoclub.com/FSM/Hardbody/d21_truck_1989.pdf It's 112MB, so you may want to right click -> save as.

Just try the fluid alone first, if it still chatters on figure-eight turns then add some as required. If you don't end up needing it, return it.

Yes, overfilling by over a quart or so is not good.

Just under 3 quarts.

That's fine.

I've used both Techron and Gumout Regane; since both contain PEA, they both work well as far as I can tell. Techron can usually be found as BOGO free at some auto parts store every month, but if not I usually just get Gumout Regane from WalMart since it can treat more gallons than Techron for the same or cheaper price.

Most "injector cleaners" are more or less useless, and contain mostly kerosene. Fuel system cleaners such as Chevron Techron, Gumout Regane, and Redline SI-1 are much more effective since they contain PEA (polyether amine) which is a proven cleaner that doesn't leave deposits behind such as solvents would. And when a fuel system cleaner is in the gas tank, many shorter city trips (but not so short as to not reach operating temperature) are ideal since the time spent sitting between trips allows the cleaner to soak in and work better.

Even R50s through 2004 only specify GL-4 or ATF for the transfer case. Doesn't GL-4 have more anti-wear additives anyway? I don't remember right now.

The FSM only specifies GL-4, so I would not chance using GL-5 in the transfer case.

Engine coolant temperature sensor?

There is a TSB about ECM reprogramming if rear oxygen sensor codes pop back up after replacement. See here.

Cut open your used oil filters and make sure there wasn't any failure of the filtering media, like a blowout for example. It's rare but that could be a possibility I'd imagine. You'll also see if the filter has caught any big chunks of stuff that way too.

Are you sure they're magnetic? Try to pick them up with a magnet. Which NAPA filter? They have several lines of filters.

Upload them to www.imgur.com What is your typical oil change interval? What oil & filter do you use? Is the air intake secure without any leaks or possible dirt entry points? Air filter present?

Anything will make noise with low or no lube. If you don't know the last time the diff fluid was changed, just change it. Many fluids already have LS additive in them already. If you live near Advance Auto Parts, you can get Mobil 1 75W-90 for cheap if you order online using discount codes (Google for them).

You can run MT-90 in the transfer case, it specifies ATF or GL-4 (but you can't mix the two). Redline's gear oils (i.e. normal 75W-90) are great too, perhaps you could use those in the diffs too. Unless you plan on off-roading and have a chance of potential water entry, then I'd suggest using a cheaper conventional gear lube and changing it out more frequently and whenever there was a chance of water entry.

Lucas Oil Stabailizer is monograde gear lube without any additives, so all it does is thicken the lube and dilute the additive package. I can't see how things would become "dry" after extended periods of sitting, oil still clings pretty well all on its own... in a diff or manual trans I guess it's okay to use, but I would never use it in an engine.

No, all this does is add a resistor to the intake air temperature sensor. All it does is lighten your wallet.

Lucas gear oil is garbage. Based on this white paper and Advance Auto's great discount codes, I would use Mobil 1 75W-90 as it resulted in the best score behind Amsoil SVG 75W-90 and the only "failure" of M1 75W-90 was shearing just barely under spec after some use. Maybe buy a fluid pump too to help fill the diffs. For the transfer case, use any synthetic ATF claiming to meet Dexron III specifications. AAP discontinued use of discount codes for most of the ATFs they stock, unfortunately. Valvoline MaxLife should be a good option, it has a beefy additive package compared to many other ATFs; see this table. Castrol HM is nothing special I think, they have mediocre metallic additive packages similar to Valvoline's and is overpriced for what you get IMO. I guess they have more marketing to pay for. See here for a virgin oil analysis of Castrol HM (albeit it's 10W-30 but the additives should be almost identical between the two). You can see a table of several conventional oils' virgin analyses here, but I wouldn't overthink it as any API SN oil will easily be capable of going at least 5k miles in a clean, mechanically sound engine. I would use Mobil Super 5000 5W-30 to save the $5 or whatever the price difference is. NAPA Gold filters are excellent, no need to change that. Amazon has Redline MT90 as well, it might be cheaper than your NAPA. Thought about changing your brake fluid, power steering fluid, coolant, fuel filter, PCV valve?

They are twist bases I think.

Go for it, you can run it year-round if you want. It should work fine. I would run it out to at least 6k miles to get your money's worth.

http://www.nicoclub.com/FSM/Pathfinder/1995_Pathfinder/

See page EC-464 of the factory service manual for possible causes. Rule out intake air leaks first as that's the simplest.

Relax dude, the OP had some valid questions. The owner's manual says nothing about replacing the crush washer or prefilling the oil filter or even removing the engine undercover to access the oil filter.