New owner, rear differential possibly locked?

[deanpence]

My '93 Pathfinder rumbles/shakes when turning at low speeds and has a high whine coming from the rear starting somewhere around 55mph.

 

I'm unfortunately pretty clueless with cars (though I'm willing to learn), so I took it to a repair shop to see if they could diagnose the problem(s). I think they were dumbing it down for me, but they said it seemed like the rear wheels were stuck in 4WD and would only rotate at exactly the same speed. They also said they couldn't repair it and to take it to a 4x4 shop.

 

From what I understand, 4WD basically locks the differential so that all wheels rotate with the same speed and torque, but that 2WD should unlock the rear differential and engage the LSD if I have it. Is that anything close to correct? (Please no flogging; just pointing and laughing.)

 

Any ideas what might be causing the differential to behave this way?

Edited August 9, 2011 by deanpence

[MY1PATH]

pathfinders did not come with locking differentials. they were open (drive goes to the wheel of least resistance) and LSD.

If your pathfinder is LSD (look for an orange sticker on the back of the axle) it may act locked if it has the wrong fluid or no fluid. It will also wear out the LSD.

if you roll down the window can you hear the tires chirp when driving in tight circles?

Try re-filling it with some API GL-5 75w90 or 80w90 and make sure it says LSD on the label.

[Slartibartfast]

The four wheel drive engages the front end, which causes the front and rear to spin at the same speeds, but doesn't do anything with the differentials. (The diff cages spin at the same speed, but the wheel speed can change side to side, as the differentials are still open.) If it's stuck in 4x4 and you try to turn on dry pavement, yes, it'll chirp a bit/drag the tires/not do very well. When you turn, the front and rear tires follow different paths (just like the tires on either side) only there's no differential to compensate, so something has to give (usually the tires slide). This isn't a problem on wet/snowy/muddy/loose roads and trails, because the tires are slipping anyway (that's why you need 4x4).

 

Just to get the stupid questions out of the way: is the green 4x4 light off? Is the 4x4 lever (says 2h, 4h, N, 4lo) pushed all the way forward? Have you tried driving it backwards for ten feet or so? Does it have the stock automatic hubs, or does it have manual hubs (turn by hand)? The front end stays engaged when you turn the 4x4 off until you drive it backwards a bit, and if the hubs are still locked, it's still in 4x.

 

The owner's manual goes over working the 4x4, and if you don't have the manual, check above the driver's side sun visor, there should be a cliff's notes version in the clear pocket.

 

The whine at 55 might be related, or it might not. If you notice it even when going dead straight it could be a dragging brake or a wheel bearing or something, or of course it could just be the 4x4 complaining.

 

There is the chance that your rear axle is actually locked up (and both rear wheels spin at the same speed no matter what). Besides a botched LSD, I guess somebody might have locked it up for off-road use (probably with a welder). If this is the case... your rear end could be bad. (The shop guys hopefully would've caught that, though, rather than going on about your 4x4.)

 

Also keep in mind I'm not a mechanic, so I could be totally full of it. Good luck!

Edited August 9, 2011 by Slartibartfast

[adamzan]

If there is a whining noise it sounds like it could be low on fluid. Check that asap!

[deanpence]

The four wheel drive engages the front end, which causes the front and rear to spin at the same speeds, but doesn't do anything with the differentials.

 

That's very good to know. I figured as such. My knowledge of the details of how a transmission works is almost nil so I'm glad my intuition was right here.

 

Just to get the stupid questions out of the way: is the green 4x4 light off? Is the 4x4 lever (says 2h, 4h, N, 4lo) pushed all the way forward?

 

No problem with stupid questions. I need stupid questions. But I did check these before posting. The green 4x4 light is off, and the 4x4 lever is all the way forward in the 2H position.

 

Have you tried driving it backwards for ten feet or so? Does it have the stock automatic hubs, or does it have manual hubs (turn by hand)? The front end stays engaged when you turn the 4x4 off until you drive it backwards a bit, and if the hubs are still locked, it's still in 4x.

 

I do have the stock automatic hubs. I haven't tried driving it backwards. I'll give that a whirl.

 

The owner's manual goes over working the 4x4, and if you don't have the manual, check above the driver's side sun visor, there should be a cliff's notes version in the clear pocket.

 

Yeah, that's what I did before posting to idiot check.

 

The whine at 55 might be related, or it might not. If you notice it even when going dead straight it could be a dragging brake or a wheel bearing or something, or of course it could just be the 4x4 complaining.

 

The mechanic who looked at it seemed to think they were related, but he may not have even worried about the whine after he figured out he couldn't fix this problem.

 

There is the chance that your rear axle is actually locked up (and both rear wheels spin at the same speed no matter what). Besides a botched LSD, I guess somebody might have locked it up for off-road use (probably with a welder). If this is the case... your rear end could be bad. (The shop guys hopefully would've caught that, though, rather than going on about your 4x4.)

 

I do hope they would have caught this, but now that the sun's gone down, and it's not over 100 degrees, I'll give it a look.

[deanpence]

If there is a whining noise it sounds like it could be low on fluid. Check that asap!

 

Had an oil change in the past week, and they claim that they checked the transmition fluid. I double-checked earlier today, though I still need to double-check with a warm engine. It at least looked nice and red and looked full with a cold engine.

[deanpence]

If your pathfinder is LSD (look for an orange sticker on the back of the axle) it may act locked if it has the wrong fluid or no fluid. It will also wear out the LSD.

 

That's what I spent most of today trying to find out. Believe it or not, I can get dehydrated really fast in this heat, so I didn't actually go look—and I didn't know what to look for. I'll check it out.

 

if you roll down the window can you hear the tires chirp when driving in tight circles?

 

I'll try the parking lot again with the window rolled down. I can definitely *feel* what feels like a tire trying to slip—or perhaps actually slipping.

[sewebster]

Had an oil change in the past week, and they claim that they checked the transmition fluid. I double-checked earlier today, though I still need to double-check with a warm engine. It at least looked nice and red and looked full with a cold engine.

 

The rear diff has separate gear oil in it. It has a check port on the back.. you remove the plug and see if the oil level is up to the hole.

[deanpence]

Perhaps we should start with a basic: How do I identify the rear differential? I'm just plain ignorant here. Is it on/a part of the rear axle?

 

Edit:

Okay, I *think* I've figured it out. In this case, I've got a lot of gunk to clean off to try to see if there's a label about it needing LSD fluid. I'll try to find the check port as well.

Edited August 10, 2011 by deanpence

[deanpence]

Update: Rear differential is an LSD. Receipt from the oil change says they checked the "Differential/TransAx", but it doesn't get any more specific than that. Given the level of grime accumulated around the check port and drain port (?), and the fact that the orange label indicating LSD oil use only was completely obscured with grime, I doubt they even looked at it.

 

I can't open the check port currently. It seems to be threaded, and I measured the square hole at about 1.25cm or 9/16"; since I have nothing that can open it, I'm going to go see what Walmart has, maybe a socket wrench head just so I can check the level. I'm really not sure what I'm supposed to use to unscrew it.

 

1) If the level is below the level of the check port, do I fill it using the same port?

 

2) If the level is fine, does it make sense just to drain and replace the fluid just in case the current fluid is not for an LSD? At the very least, this would eliminate one possible cause of the low-speed steering.

 

Please bring some experience to my utter guesses.

[Towncivilian]

Your transmission fluid should not be at the full line with the engine off and cold, you need to check it on a flat surface with parking brake engaged after driving for 5 minutes around town once the engine is warmed up, and after selecting every gear starting from P and returning to P.

 

 

The differential should have a drain and fill plug. The drain plug should be magnetic and will probably have some ferrous material collected on it. I don't know what size the WD21 diff plugs are, but my R50's seemed to be 1/2" drive. Mine were so difficult to get off that I had the local dealer perform the service with my own supplied fluid and new drain & fill plugs for $25 (of course, factoring in the cost of gear oil and new plugs, it totals to around $80).

 

To fill the diff, fill it to the bottom of the fill plug (basically stop once it starts overflowing). 3 quarts of Mobil 1 75w-90 synthetic gear oil is $22ish after discount codes if ordered online from Advance Auto Parts and is a very good fluid.

 

 

Instructions taken from a '94 FSM, but it should be identical.

Edited August 10, 2011 by Towncivilian

[sewebster]

Yeah, if you suspect the fluid could be a problem, then drain it out and put in new stuff for an LSD. The plugs are 1/2" but they can be stuck pretty good... The drain plug is on the bottom. the fill/check plug is on the rear side. Make sure you can get the fill plug out before you take out the drain plug or else you might be stuck unable to fill it up and drive

[deanpence]

It looks like getting that drain plug open is going to be extremely difficult. That plug is on there incredibly tight. I may have to resort to a dealer or other mechanic for this. It also looks like finding the differential oil will require some hunting.

 

Any advice to a newbie on getting a hard-to-start plug going? Not sure if I want to be using a hammer in there so close to the fuel tank and a fragile-looking hose/conduit above the differential. I'm just using a 6-inch socket wrench with a 1/2" drive.

[Towncivilian]

Try using some PB Blaster, spray it on every day for a few days. If that doesn't help, applying heat with a propane torch or something would. Or just see if your local Nissan dealer will do it for the price of an oil change ($25 + disposal fees, tax, etc; ultimately costed $29.29 for me) if you supply your own fluid. Like I said, 3 quarts of Mobil 1 75W-90 online from Advance Auto Parts with code P20 comes out to about $22 after tax if you pick up your order. FWIW I couldn't get either plug loose with a lot of PB Blaster and a 22" breaker bar... I wasn't comfortable with applying heat, and other shops wanted $90 for a diff service until I asked Nissan what they would charge if I brought my own fluid, and $25 was a pleasant surprise!

Edited August 10, 2011 by Towncivilian

[deanpence]

@Towncivilian: Cool, thanks. I think I'll give them a call tomorrow. If the fluid is low, I'd rather get it changed/filled quickly; this is my only car.

 

Advance Auto Parts doesn't exist here, but I can get a similar price on Valvoline 75w90 at O'Reilly, Napa, or Auto Zone, and at just a tad more expensive for the Mobile 1 synthetic. It even looks like at least Auto Zone has some in stock.

 

I'm just assuming that a Nissan dealer has magic make-it-turn sauce that they apply.

Edited August 10, 2011 by deanpence

[Towncivilian]

Huh, strange. I figured they were a national chain. Sorry for insisting on AAP, but their online discount codes are simply irresistible sometimes. Pretty much any name-brand gear lube will do you well as long as it says it's LSD compatible on the bottle, and most are nowadays, especially if they're synthetic. Good luck!

Edited August 10, 2011 by Towncivilian

[silverton]

I'm afraid I have never met someone of your level of mechanical knowledge. I like it! Fresh blood to teach right!

 

As for the transmission fluid, I'm sure it's fine. The differential is on the rear axle in the very middle. Seeing as you have an SE, a limited slip came standard. The drain and fill plugs are a standard 1/2" size. You will need something longer than a 6" bar to break it free, it's in there good for sure, and I'll even put money on it that someone used thread locker on it. My personal favorite is my 2.5' long breaker bar, if that doesn't knoc a bolt free, it needs to be cut off. HAH!

 

Basically the only time a differential is going to whine, is if it's low on fluid or worn out. My bet is going to be low on fluid from your description of all the gunk on the pumpkin (that's what a differentials codename is!) If you feel you aren't quite up to the job, take it to a quick lube place, and specifically ask for a differential drain and fill.

[deanpence]

In the meantime, here's a short video I made that *might* give folks a better idea of what things sound like when I turn at low speeds. Not sure if it'll come through though:

 

http://dl.dropbox.com/u/3681334/pathfinder%20steering%20-%202011-08-09.m4v

 

Tires don't squeal/chirp; everything just growls and shakes. Rarely I hear a groaning from the engine compartment.

[silverton]

I THINK I'm hearing what you're talking about, but it's difficult to make it out. I hear more inside noise, than outside noise. Perhaps set your camera on the ground in a parking lot, and drive in a tire circle around it.

 

I'm going to bet that your differential just needs servicing though. A quicklube place will be able to handle that just fine, be sure to mention that it is a LSD differential.

[sewebster]

When I first got my truck I was pretty clueless and it was super noisy and shaky. Turned out that I basically needed to replace all my shocks (not only were they 20 years old, but the bushings were gone, so they were super clunky) and a bunch of suspension bushings. It's way better now. Still, worth getting the diff figured out. You should also try to make sure you aren't stuck in 4wd somehow. I'm trying to think of a good way that doesn't involve jacking the front of the truck. If you have a jack and jackstands then you could jack up and support the front and then go under and try to turn the front driveshaft. If you can turn it, (at least until the hubs lock) then you aren't in 4wd. If you can't turn it at all, then you could be stuck in 4wd (you wouldn't be able to turn it then because to do so you'd have to also turn the rear wheels and they are stuck on the ground). Regarding the 4wd shifter... there has been some confusion in the past from some people (there is a thread on it somewhere). You should try to familiarize yourself with all the positions. You have to push down on the knob to get in and out of 4-lo. Hopefully you aren't driving around in 4-lo

[deanpence]

@sewebster: I'm pretty certain I'm not driving in 4WD. The manual's pretty clear on how to shift from 2HI/4HI/4LO, the shifter is up past 4HI at 2HI, and the light is off. Plus I drove it in reverse for a good 20 feet last night and then drove it a mile home, just for good measure. If it's stuck in 4WD, something else has got to be wrong (hubs?).

 

I'm about to take it in to get the differential oil changed. I can get it all done for around $50, so it's not too bad. I guess we'll see if that solves it.

[deanpence]

Dear gods. I hadn't realized how much rear axle noise I had at lower speeds 'til now. Just driving home from the lube shop at 30-40mph, I heard wind noise from the sun roof for the first time. But in order not to become a victim of confirmation bias, I'll try some highway driving tonight when the temperature drops below 90 and see how the noise is at higher speeds.

 

Thanks to all of you for your magnificent help! Even if this didn't solve the problem completely—which it very may well have done—this has definitely made a huge improvement.

[deanpence]

(Oops. Just noticed this thread is under the wrong topic. My Pathy is a '93.)

 

Okay.

 

I think the issue with the rear wheels rotating at the same speed is solved; it definitely feels that way. At very low speeds (0 - 15mph or so), when I was feeling it the most, steering feels extremely smooth. The wheel turns smoothly, the tires don't skid a bit, nothing.

 

The rear-axle noise is still there, though it's definitely much more quiet. Up to 60mph or so, I can hear wind noise, the engine (when accelerating), and it no longer "feels" like the auto transmission is taking way too long to shift. The rear axle noise starts out at a lower pitch and gradually gets higher and louder the faster the Pathy's going; I guess I was partly using that noise as part of my regular cues about when the transmission should shift. At around 55-65mph or so, the noise gets pretty loud (though it could be because that pitch range is resonating with something in the body). At 70mph, the Pathy and the steering wheel shake just a bit (though I guess this may be a separate problem).

 

The differential job the lube place did looks fine. They didn't replace the plugs (I don't think), but nothing's leaking or anything obvious (to me).

 

Any ideas? Maybe I should start a new thread for this issue if it's a different problem.

Edited August 11, 2011 by deanpence

[Mauitrailguy]

(Oops. Just noticed this thread is under the wrong topic. My Pathy is a '93.)

 

Okay.

 

I think the issue with the rear wheels rotating at the same speed is solved; it definitely feels that way. At very low speeds (0 - 15mph or so), when I was feeling it the most, steering feels extremely smooth. The wheel turns smoothly, the tires don't skid a bit, nothing.

 

The rear-axle noise is still there, though it's definitely much more quiet. Up to 60mph or so, I can hear wind noise, the engine (when accelerating), and it no longer "feels" like the auto transmission is taking way too long to shift. The rear axle noise starts out at a lower pitch and gradually gets higher and louder the faster the Pathy's going; I guess I was partly using that noise as part of my regular cues about when the transmission should shift. At around 55-65mph or so, the noise gets pretty loud (though it could be because that pitch range is resonating with something in the body). At 70mph, the Pathy and the steering wheel shake just a bit (though I guess this may be a separate problem).

 

The differential job the lube place did looks fine. They didn't replace the plugs (I don't think), but nothing's leaking or anything obvious (to me).

 

Any ideas? Maybe I should start a new thread for this issue if it's a different problem.

 

Was it leaking from where the driveshaft hooks up? Could be a bad pinion bearing..