Differential problem Infiniti QX4? w/ 4wd

[ltslimjim]

Last summer a lady at work with a 2000 QX4 4wd had a failure of a spring to the throttle plate, which lead to the engine continuing to push forward and the car needing to brake hard to stay 'relatively' under control.

See previous thread here:

http://bobistheoilguy.com/forums/ubbthre...322#Post2399322

Basically, her rear differential seems to be causing issues now. I don't believe she has ever gotten the fluid replaced in either the front or rear, not sure if a 'transfer case' would be relative to this or only P/S system? I'm new, forgive me. lol

I suggested since she had to fight the vehicle accelerating, plus the axle probably having the original fluid still, that the differential is the issue.

She notices it shifts from the rear axle to one side or the other but one at a time(this is the rear wheel drive not with 4x4 turned on), randomly/alternatively etc.(usually while on the highway at generally a constant rate of speeds and the symptom happens relative to accelerating and decelerating at those times)

I'm here to ask about fluid replacement for this vehicle and what she should know should her mechanic install the wrong fluid by 'chance'. Someone else is doing this job, probably tomorrow.

I suggested to let it be inspected and if nothing major seems out of order, to try a fluid change. It sounded like the guy has worked with 'differentials' before(the shop initially didnt know what this symptom was apparently until I suggested this BUT they may not have known what happened last summer with her vehicle and the WOT/drive axle vs all brakes applied).

IMO, this is a combination of that, with lapsed service, etc.

The shop claims nothing else seems to be the reason, so it seems straight forward.

Lastly, in the event it's really bad I suppose a junk yard part without rear end damage of the same model(or p/n essentially) with a couple fluid changes might suffice?

She wants to fix this before it becomes a failed unit. Apparently, the symptoms have happened increasingly for a few months, only recently becoming more consistent with the relative speeds.

Thanks.

PS: She does use the 4wd feature from time to time, but this is happening with it disengaged. The tires on the vehicle I 'believe' are the stock size/original wheels etc.

 

[Towncivilian]

Wobbling at highway speeds is caused by worn rear trailing arm bushings. Replace upper and lower bushings or the entire trailing arms. Check RockAuto for some decently priced Dorman trailing arms.

This QX4 has an H233B rear axle with either 4.363 or 4.636 gearing, possibly with LSD. Check the certification plate on the passenger side firewall. "HG43" is 4.363 and "HG46" is 4.636 gearing. The factory fill was in my Pathfinder's H233B for 123k miles and my differential is fine. I doubt this issue is fluid related.

 

[rpn453]

I don't think a differential would cause an issue like this, but I can't say for sure.

Are the tires all the same? I had a '98 Pathfinder - same basic vehicle - that felt like the back end was trying to randomly steer me off the road when I temporarily had a different set of tires on the back compared to the front. Worn bushings would do similar things.

 

[ltslimjim]

The lady describes it as being violent shift to one side...one of the sides of the rear axle at a time.

Only one side does this each event, not a constant 'shimmy shake'. It happens at cruising speed and seems to be more symptomatic when its wanting to happen if you try to change speeds much immediately.

Apparently, the shop has looked at everything aside from differential, but I could also recommend them looking at the rear trailing arm for issues.

Why wouldn't a differential of this type in this vehicle possibly having this apparent slippage? Is that not what is happening?

What is a slipping differential or other type of symptom from a problematic diff like?

I thought I had a good idea, but I suppose having them check the bushings on the rear isn't a bad idea. Something could be broke. It just sounded like they already did this, but worth asking. Thanks.

 

[artificialist]

The last time I dealt with a violent shake from one of those cars, the bushings that held the power steering rack to the car frame had become weak.

Anyway, all the other causes listed are possible as well.

 

[rpn453]

Originally Posted By: ltslimjim
Why wouldn't a differential of this type in this vehicle possibly having this apparent slippage? Is that not what is happening?

What is a slipping differential or other type of symptom from a problematic diff like?


It's just solid gears. Not really any way for it to slip. I suppose it's possible a worn or failed internal part could cause binding, which could alternate from side to side. That would be highly unusual though, and I'd expect a lot of noise before anything actually affects driveability, with rapid progression of failure. Differential internals require a lot of precision and aren't very tolerant of problems.

If she's on the original gear oil she's long overdue for a change anyway. There is likely a drain plug on that diff and I'd expect to see something ugly pour out if it's having issues, but popping the cover and having a look at everything would tell you for sure. If the diff is the source of this problem, the signs should be obvious from a visual inspection.

The transfer case is unrelated to this problem, as it is completely disconnected from the drivetrain in 2WD. It wouldn't be a bad idea to get new fluid in the transfer case and front diff since it's very easy to do.

My '98 had a limited slip on the back so it needed a limited slip additive or an appropriate GL-5. There was a sticker right on the diff warning of this. Regular GL-5 could cause issues with the function of the limited slip, but nothing that would affect driveability in any major way, like the problems you describe. It would just reduce the smoothness, effectiveness, and lifespan of the limited slip.

If everything seems tight back there and the differential looks okay, I'd focus on the tires. Check pressures, move them around, or even replace them if they're nearing the end of life. I've driven many vehicles with problematic or mismatched tires and that Pathfinder was the only vehicle where the tires made it difficult to stay in a lane at highway speeds. And there was nothing wrong with any of those tires; they were just mismatched from front to back. It would have felt very strange to actually have a defective tire on that back axle.

 

[ltslimjim]

Thank you very much for this information. Makes perfect sense. Exactly what I needed.

 

[Towncivilian]

There are definitely drain plugs on the differentials of that QX4. The drain & fill plugs are 13mm plugs; use a socket like the one found in this Harbor Freight set. A 1/2" drive tool may start to disfigure the plug as was the case for me, so I'd suggest getting this 13mm socket and some penetrating oil. I too would suggest changing out the fluid if history is unknown - same for the transfer case. Find fluid quantities in the FSM or in this thread.

Let us know if you manage to fix the problem!

 

[ltslimjim]

Okay, so what I heard was the frustration of the issue and it could be anything from warped rotors to some sort of loose endlink or bent/something affected a small pull to one side. Bushing looked fine, differential was just drained/re-filled as needed but no bad wear metals etc with the drain.

Tires are the correct size, but they were installed within this past year.

From the previous smoking brakes to stop with the stuck open throttle problem happening while driving, I'd image its related to the brakes somehow if the control arms/endlinks and whatever sort of sway bar may exist are checking out.

She's going to have the tires rotated and things look at. Might just need a new rotor? Anyway, just updating. Thanks for the help. Sounds more clear now.

 

[Towncivilian]

I wouldn't discount the rear drum brakes; it's possible something is sticking. Have them cleaned, lubed, adjusted, and measured to ensure the shoes & drums are still within tolerance. A Nissan dealer did a rear brake service for $40 + tax about a year ago on my Pathfinder, though I don't know exactly what they did since I wasn't watching. The brake pedal did feel firmer afterwards, however. Even if the rear drums check out, it's still not a bad idea given the apparent lack of preventative maintenance on this vehicle.

 

[artificialist]

Originally Posted By: Towncivilian
I wouldn't discount the rear drum brakes; it's possible something is sticking. Have them cleaned, lubed, adjusted, and measured to ensure the shoes & drums are still within tolerance. A Nissan dealer did a rear brake service for $40 + tax about a year ago on my Pathfinder, though I don't know exactly what they did since I wasn't watching. The brake pedal did feel firmer afterwards, however. Even if the rear drums check out, it's still not a bad idea given the apparent lack of preventative maintenance on this vehicle.


They probably treated the drum brakes with brake cleaner, and then adjusted shoe-to-drum clearance, so less brake shoe movement is needed to apply friction to the drum.

 

[ltslimjim]

Update: It WAS the control arms and bushings. The shop originally claimed they were fine...anyway, it's finally been properly diagnosed.

 

[rpn453]

Good to hear you've got it solved.

 

[Towncivilian]

Told you!

I'm glad you got it fixed.

 

[ltslimjim]

Well, it's the co-workers vehicle. I never got to drive it myself b/c of scheduling issues, I totally miss-understood her initial complaint regarding the symptoms since it's all by description anyway.

I was working with her to ask the shop what they have checked, even forwarding information regarding the LCA and bushings, etc, and it seemed like the only other place to check was the differential...fail.

Oh well, the front needs a fluid change now, too. So it wasn't money wasted. 150k on probably the original differential fluid, and it's a 4x4 unit. Going to help her identify the transfer case fluid to get as well as remind to get an oil analysis with her next oil change since she had an overheat recently. (busted radiator hose)

 

[Towncivilian]

Transfer fluid: 2.32 quarts
Use Nissan Matic D or equivalent Dexron III/Mercon, or GL-4 gear oil. ATF is used in the factory. Do not mix ATF and gear oil in the transfer case.

I'd go with ATF; something tells me this vehicle doesn't really go off-road much and shouldn't need any additional protection that might be offered by the more difficult to find GL-4 gear oil.

Front differential: 2.17 quarts
Use GL-5 fluid, FSM says 80W-90 is preferred.

 

[ltslimjim]

^Any need to add a limited slip type additive being that is 4-wheel drive? Learning about differential types. Thanks.

Good idea on using ATF in the transfer case, especially since it probably still has the FF as well. However, at this point the owner has thought about selling the vehicle for something more fuel efficient.

Ugh, you wouldn't believe the tar like substance on the throttle plate...no wonder the throttle spring broke! I just hate that no other mechanic in 150,000 miles before I ever get to the vehicle 'never' checked the throttle body...ever.

Fail. She could have died or killed someone!

 

[Towncivilian]

No, front diff should not need any LSD additive. Is there a bright orange "LSD" sticker on the rear diff cover? If so, the rear might need additive if the new fluid doesn't already have LS additive, or if it is chattering.

Strange that there was so much garbage on the throttle plate. My Pathfinder never has much build up, although that might be due to the engine difference, not sure.

Does this engine consume any oil?

 

[ltslimjim]

Originally Posted By: Towncivilian
No, front diff should not need any LSD additive. Is there a bright orange "LSD" sticker on the rear diff cover? If so, the rear might need additive if the new fluid doesn't already have LS additive, or if it is chattering.

Strange that there was so much garbage on the throttle plate. My Pathfinder never has much build up, although that might be due to the engine difference, not sure.

Does this engine consume any oil?


I honestly can't tell you.

If so, not too much. It's always on the dipstick. Perhaps 1/2 quart every 5,000?

I had began getting her vehicle on a 5,000 mile OCI, using M1 the few times now I've done some various jobs on the vehicle including oil changes. Using Mobil 1 Extended Performance oil filter changed every other oil change. (10,000 miles on the filter)

Of course, I also had the OE PCV valve replaced with another OE and replaced her fuel filter; which was due for it.

Since the overheat a month or so ago, I set up a date to do the oil change and sample, to post on here but our plans fell through twice apparently. Not sure what's up. I'll make it a note to see if she had it performed elsewhere.

Lastly, when I replaced the spark plugs on this vehicle(which had new Beck/Arnley branded plug wires at a 100k tune up) there was a lot of carbon depositing all around the threads. I've since encouraged the use of a PEA FSC like Red Line SI-1 the tank before an oil change for her in hopes of combating CC deposits. Especially based on how lame the TB was caked, especially the plate. It was just sickening...

(that was before the overheat btw, which wound up being from a hole that had a slow weep which turned into a gush in the radiator hose, I had monitored her coolant level and didn't notice a discrepancy, she uses other shops that have lifts,etc and I essentially said she'd have to go elsewhere to determine the real issue, at the time it appeared to be a water leak of some sort but didn't smell of anti-freeze)

 

[Towncivilian]

I was going to suggest changing the PCV valve if there was any oil consumption. It's good that you already have.

How's the transmission fluid & PSF look?

There's most likely a cabin air filter behind the glove box. If it's anything like the other maintenance items, it's probably the original one and is absolutely filthy. If your coworker complains of a smell or poor blower motor performance, look into changing it. See here if you'd like a guide.