Slartibartfast

Going through flasher units sounds like a short to me. What I'd do is, put your meter to ohms, then check it from the plug to a bare spot on the body/frame. One side should go to ground, and the other shouldn't. If neither does, you have a busted ground wire; if both do, they're shorted together somewhere. For the parking lights, do the tail lights work? They share a contact in the headlight switch, so it both are out, I'd try cleaning that contact (center one IIRC). If it's just the front ones, start following wiring, something must've gotten pinched in the collision.

Wherever you stuff it, make sure you can get to it to read codes!

Is the check engine light on? Any busted vacuum lines?

A tip for putting doors back on, don't hold them up by the handles... that's how I broke mine.

Don't use WD40 on a MAF. There are special cleaners that won't leave a residue. I used denatured alcohol without issue. The MAF works by heating up those little wires and judging how much the air passing cools them, so if they get a burned-on coating of oil from the WD40, the sensor won't work as well. And yeah, I assume the black wire's ground. If in doubt you can test it pretty easy with a voltmeter. Shouldn't be voltage between it and ground (negative battery terminal or a clean spot on the body).

Maybe the DE block is thicker?

Also check the fluid level in the brake master cylinder. I don't remember if it was the ABS light or the BRAKE light but one of 'em came on when my MC started leaking.

Fair enough.

The MAF connector is sometimes a problem, particularly its ground. So +1 on repairing its hacked up wiring. Some people run the ground wire right to the body and say it helps. The splices sound to me like the PO tried to hook one of those stupid "fuel saver" resistor kits to it, and in the process knackered the connector and exposed the wires to corrosion. You might pull the sensor off and take a look at it, too, make sure it hasn't had anything harebrained done to it.

I didn't have to cut anything when I pulled the driver's door (power everything) off my WD. All the wiring had plugs... not easy plugs to get to, and certainly not easy plugs to stick through the rubber boots and fish through the bodywork, but plugs nevertheless. I would expect the R50 to be the same.

No problem, I wish I'd known this stuff going into mine! Maybe I wouldn't have ended up lying on my back at three in the morning, holding the tank up with my knees and cursing as I tried to get the bolt threads to catch... Speaking of the hatch, here's how to get to it. First remove the rear cargo hooks from the floor (should have two phillips screws each). Then remove the trim piece that the hatch striker sticks through. They're Phillips screws but they're plastic, and they're threaded into plastic, so don't push too hard on them or they'll just skip. I find a flat driver actually works best for them. That piece pulls out, and then the carpet should just pull out from under the side panels and around the jack holder. Push it out of your way and you should see the hatch, held down by four bolts. The wiring coming out of the pump isn't the plug, that's further down the wires (towards the back of the tank IIRC). Good luck. Oh, and get nuts and washers to go with those bolts... it's tough to reuse the capture nuts once you've drilled them out, and the stock washers are attached to the bolts.

The white powder in the M30 ecu sounds like water (and whatever was dissolved in it) got trapped inside the ECU and ate away at it. If your ECU still works, I'd open it up and have a go at it with contact cleaner or rubbing alcohol to wash out any remaining muddy water. Make sure it's entirely dry before you put it back together. And then, yeah, get it off the floor! I've been surprised at how much abuse electronics can bounce back from. Somebody at the community college I went to spilled a soft drink into one of the school's laptops, which of course made it quit working. The school figured it was shot and let me have a go at it. I cleaned out the sticky nastiness inside and got the hardware to respond, the school's tech support person fixed a few driver files, and last I heard, it was back in service. That's probably the only time I've been impressed with a Dell computer!

^ same story as mine. I don't think I really could've gotten putty into there if I'd tried. Maybe capillary action would suck epoxy or something into the seam from the outside (that's got to be how water got in and rusted out the seam), but I imagine the leaking gas would prevent it from sticking properly. If you do try to fix the tank, drain it completely and let it air out for a day or two to be on the safe side. Do what you have to, but by the time you've pulled the tank, cleaned it, bodged it, and stuck it back in, you won't want to do it again! You could siphon out the fill hole, but there's a hinged baffle that'll give you a hard time (and I think it's way too narrow for most hoses you'd have laying around). I think it would be easier to remove the fuel pump from the inside (access hatch under the carpet) and siphon the fuel out through there. Remember ventilation! I just drove around until I only had five gallons or so in the bottom, dropped the tank, and poured it out into a gas can for later. I picked up a tank from eBay (the brand was Wiggley's, don't remember the seller) because the shipping cost from Rockauto was as much as the tank for some reason. The bolt holes weren't aligned right, the included O-ring for the pump was too big to fit, and the flange to hold the O-ring was too kinked to seal anyway. I got it in finally (with a lot of swearing, grinding, and Permatex), but only because I didn't want to let it win. Sounds like the RockAuto tank is a much better product. I never bothered with the battery cable, but I did pull the fuel pump fuse (with the engine running at about 2k rpm to discharge the fuel pressure in the lines). Then I pulled the fuel lines from the pump via the access hatch, unplugged the pump, and then dealt with the other hoses (filler and two breathers) however I could get at them. IIRC I ended up removing the filler neck from the fender to help get that tube free. I wanted to pull the passenger's side rear wheel off for easier access, but I had the truck up on ramps, so I had to work around it. I ended up removing both rear fender flares instead, partially because they blocked my reach, and partially because I kept hitting my head and arms on the mud flaps. If you don't have a helper for lowering the tank, make sure you've got something set up to catch it and support it while you undo the last bolt or two (and to hold the new tank in while you bolt it up). I used the factory bottle jack and some boards. Make sure there's a board between the jack and the tank or you'll dent the tank (guess how I found that out). One last thing... be ready to drill out and replace the tank bolts. I think I broke four of the six trying to remove them. They'd pop loose, then bind back up, pop a few more times, and then shear off. Hopefully yours treat you better!

I don't know what you've read, but the diagrams in the service manual (pages TF-11 and TF-43 of the '03 FSM) show no diffs. It appears that some people say "locking center diff" and "transfer case" interchangeably, which isn't correct, but could easily have gotten into an article written by someone not familiar with 4x4 drivetrains. A center diff splits power between the two axles. It can drive the front axle faster than the speed of the diff, so long as the rear axle is driven an equal measure slower. (Think of a sharp turn in a parking lot. The front axle goes farther than the rear, therefore the front diff is spinning more quickly than the rear.) A clutch type transfer case set to 'automatic' rigidly couples the rear axle to the transmission and kicks a little power to the front when the traction control tells it to. It can never drive the front axle faster than the rear, and in the parking lot scenario, it would cause torque bind if it kicked in. The front end has to coast. Also, those warnings apply to pretty much any vehicle that can lock the front and back together, regardless of design. 4x4 = torque bind on dry pavement, and going 55+ on a surface loose or slick enough to require 4x4 is inadvisable in general.

From what I've read, it's the exact same transmission, so yes, it'll work. If you can find one, a trans from an 01+ Pathy or Xterra will be stronger than the one from the '99, but either should work fine. Advise your friend to flush the old fluid and gunk out of the trans lines, and replace the transmission cooler (abandon the one in the rad and run the lines to a new cooler). The stock trans likely spat out a bunch of gunk as it died, and it's best if that doesn't get into the replacement trans.

I would ignore the knock sensor until you have the EGR sorted. That code (at least from what I've seen) tends to crop up with, and go away with, other codes, probably because other problems that throw codes screw up the air/fuel mix and lead to knocking.

The '03 FSM lists the R50 as having the same R200A front diff that most Pathfinders came with, so unless the R200A changed its spline count between gens (like the rear diff did), I don't see why you couldn't put a ZX diff in an R50. There are two transfer cases for the R50s, the TX10A (stick on the floor) and the ATX14A, which has a little knob on the dash. (I imagine this was a 'luxury' feature for the LE trim Pathy and the QX4. My dad's '03 has the manual case.) Neither transfer case includes a diff. The auto case has a wet clutch assembly inside, and when auto mode is engaged, it works as traction control, sending power to the front when the computer detects slip at the rear wheels. I'm pretty sure Subarus work similarly. Personally I like having a stick coming through the floor that's actually attached to something, but the auto feature is probably quite nice when driving on a dry road with patches of snow and ice on it. I think the auto case is the main reason the R50s came with drive plates instead of locking hubs for the front wheels. If the auto case tries to send power to the front wheels, at speed, and the front diff isn't spinning, those clutches are gonna have a bad time. IMO a locking center diff is a nicer design, but it would be heavier, more complex, and less efficient on the highway (more rotating mass, and probably no 2WD setting). I read something from a guy who'd put a Lokka in the front of his rig (not a Nissan). He said it crawled quite well but the steering got weird. That's the upside to a selectable locker... turn it off and it works like stock.

IIRC a few guys on here have access to a database where they can punch in your VIN and see what it was optioned with.

You know, I just thought of something. It started doing this after the trans swap, right? Maybe when they put the trans in, the dealer didn't get the shift cable adjusted right, so when you slot it in Drive, it's actually engaging second gear. If you watch the tachometer as you accelerate from a dead stop, does it rise and fall like it's shifting gears or just rise with speed? Dunno, just an idea.

Not a head swap, but a twin cam VG30 in a Pathy has been done: http://www.nissanpathfinders.net/forum/topic/30339-350hp-twin-turbo-1995-pathfinder-buildup/

Given that water in the brake system is a bad idea I'm going to go with no. There's probably some kind of dye that could be added, but I wouldn't use anything water based, and you'd have to be careful that whatever you found wouldn't attack the braking system or screw with the brake fluid's boiling point.

I drove mine around the yard once or twice with the door off (while doing the hinge pins), and I can see the appeal. Kind of an open-air thing. I don't think I'd be comfortable with it at 60 though!

1) ... is that a typo or is it really doing 6k down the freeway? Yeah, that ain't normal! I can only assume it's not going into third. (Auto trans, right?) There's a "power mode" switch on the dash (left of the steering wheel on mine, by the mirror adjusters) that's supposed to flash if the trans computer finds a fault. The service manual (AT section most likely) explains how to interpret the flashes into something that could help you track down the issue. 2) IIRC it mounts to the front of the frame (where the tow hooks go otherwise) and through the bumper to the brackets. The Pathfinder body sits about an inch lower on the frame than the pickup does, so you'd have to modify the lower mounts to make it sit right. 3) As far as I'm aware, the interiors are 90% the same. Obviously from the B pillar back will be different, but the front seats/console/dash/trim are the same as far as I know. The only differences I'm aware of in the running gear are the rear axle (HB is leaf sprung, Pathy is 5-linked and coil sprung, so the suspension mounts on the axle are different) and the transfer case levers are shaped a little differently because of the different body heights. Guys who body lift their Pathfinder sometimes use Hardbody shift levers because they clear the floor better. Welcome to the forum!

I tore off one of my factory hubs to figure out why it wasn't engaging right. The FSM says the two brake parts together should be 15.4 mm or more thick... mine was more like 14. I was amazed though, the bits that do the actual engaging looked mint. I got a horrible grinding noise out of the hub yesterday (like throwing it in park while moving, except from the hub), and I've gassed it and had the hubs smack into place more times than I can remember... I expected the bits that engage to be all chewed up, but they look brand new. I'm still swapping them for manuals though!

I tried to tow a friend's rig the other day, and found that in low range, with my foot off the gas, I had one front wheel and one back wheel slowly spinning on the snow/ice... I suspect that means the LSD's worn out. I guess you could jack up the back with it in park and try to turn one wheel by hand, and see what it takes to make the clutches slip.