Nissan 370Z Forum - Howling from the Differential help!

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Howling from the Differential help!

Hello everyone!

I have daily'd my Z for over 4 years and put about 65,000 miles on her since I purchased her. One of the first mods that I did was polyurethane bushings from Whiteline. The diff is the stock-non sport (read non-VLSD) diff. With no gear changes or installed LSD of any kind.

A few weekends ago I was doing some aggressive driving here in Ohio at a place called Hocking Hills trying to keep up with a C6 Z06.

It was about 90 degrees out and we drove hard for probably 3 hours on and off. (as in sometimes there would be a car in front of us and we would slow down or the road wouldn't be curvy and we'd just cruise, but always in constant motion, just not aggressive driving at all times).

Anyways as we go to stop for lunch I'm starting to notice a louder than average gear noise coming from my Z. After lunch I decide to call it a day and drive back home. On the drive on the interstate on the way back it becomes evident that I am hearing a howling from some part of the drivetrain.

I tested several things on the drive home:
-Did the noise change with speed?
-Did the noise change with Gear?
-Did the noise change with RPM (free revving with the clutch pedal pushed in)
-Did the noise change with wheel speed? (go fast, push clutch in and coast)
-Did the noise change with trans speed? (go fast, put the car in neutral and let the clutch out)

And my results were:
-changed with speed, the faster I got the louder it got
-changed with gear, but only to get faster mostly
-does not change with RPM
-does not make noise when the clutch is disengaged. (IE when the pedal is pressed in, the noise is gone)
-the noise gets louder if you are in a low torque area trying to dig out of the low torque area.

So then I got home and parked and found some drips on the ground and found the subframe was wet with what smelled and looked like gear oil.

So now everyone reading this is like: "boom your diff is F'd and leaked fluid and now you damaged the gears in the diff" which is also what I think.

But upon further inspection, none of the seals are leaking and all of the gear fluid appears to have exited the diff out the breather hose. The breather hose appears to be tucked into the rear subframe. And out of the rear subframe is where ALL of the fluid came from. The entire diff was bone dry on the exterior when I inspected it.

So on the recommendation of my coworkers, I drained and checked the fluid. The fluid was not glitter filled. The drain plug did have some metal shavings in the goop that was on it but I see that seems pretty regular based on reading other peoples changing of diff fluid threads. After draining the fluid, I refilled with the Motul 75w-90 gear oil that is recommended and drove the car.

The noise is still evident. I think that this means that the gears were damaged by the lack of fluid and the heat of driving.

SO after that long back story, my questions to you all are:
1) How did the fluid get out? It is my understanding that the fluid will heat up to the point that it will stop lubricating and then the diff will heat up itself and go boom. I've not found descriptions of the fluid like boiling over and coming out the breather...
2) How long do I have until the diff goes boom? I have a track day here in two weeks and I want it to survive at least through that event.
3) Could I have misdiagnosed my issue and the noise is coming from the trans? I think not but I didn't change my trans fluid when I did diff fluid.

I would really appreciate some input on this situation because the search function keeps finding people saying "Just put a diff cooler on it" and "you'll know when it fails because it will go boom". Which is very correct but doesn't help my analysis much.

Thanks!

You overheated the diff and it puked the fluid out the vent tube. You need a diff cooler to control the heat. MA-Motorsports sells one. If you diff is making noise you probably overheated a bearing due to lack of diff fluid (lubrication). How long do you have is anybodies guess. You will need a rebuild and I would suggest a better diff like a Wavetrac while you are at it. If I had to guess you got the pinion bearing.

Quote:

Originally Posted by kbc749 (Post 3870065)

Hello everyone!

I have daily'd my Z for over 4 years and put about 65,000 miles on her since I purchased her. One of the first mods that I did was polyurethane bushings from Whiteline. The diff is the stock-non sport (read non-VLSD) diff. With no gear changes or installed LSD of any kind.

A few weekends ago I was doing some aggressive driving here in Ohio at a place called Hocking Hills trying to keep up with a C6 Z06.

It was about 90 degrees out and we drove hard for probably 3 hours on and off. (as in sometimes there would be a car in front of us and we would slow down or the road wouldn't be curvy and we'd just cruise, but always in constant motion, just not aggressive driving at all times).

Anyways as we go to stop for lunch I'm starting to notice a louder than average gear noise coming from my Z. After lunch I decide to call it a day and drive back home. On the drive on the interstate on the way back it becomes evident that I am hearing a howling from some part of the drivetrain.

I tested several things on the drive home:

-Did the noise change with speed?

-Did the noise change with Gear?

-Did the noise change with RPM (free revving with the clutch pedal pushed in)

-Did the noise change with wheel speed? (go fast, push clutch in and coast)

-Did the noise change with trans speed? (go fast, put the car in neutral and let the clutch out)

And my results were:

-changed with speed, the faster I got the louder it got

-changed with gear, but only to get faster mostly

-does not change with RPM

-does not make noise when the clutch is disengaged. (IE when the pedal is pressed in, the noise is gone)

-the noise gets louder if you are in a low torque area trying to dig out of the low torque area.

So then I got home and parked and found some drips on the ground and found the subframe was wet with what smelled and looked like gear oil.

So now everyone reading this is like: "boom your diff is F'd and leaked fluid and now you damaged the gears in the diff" which is also what I think.

But upon further inspection, none of the seals are leaking and all of the gear fluid appears to have exited the diff out the breather hose. The breather hose appears to be tucked into the rear subframe. And out of the rear subframe is where ALL of the fluid came from. The entire diff was bone dry on the exterior when I inspected it.

So on the recommendation of my coworkers, I drained and checked the fluid. The fluid was not glitter filled. The drain plug did have some metal shavings in the goop that was on it but I see that seems pretty regular based on reading other peoples changing of diff fluid threads. After draining the fluid, I refilled with the Motul 75w-90 gear oil that is recommended and drove the car.

The noise is still evident. I think that this means that the gears were damaged by the lack of fluid and the heat of driving.

SO after that long back story, my questions to you all are:

1) How did the fluid get out? It is my understanding that the fluid will heat up to the point that it will stop lubricating and then the diff will heat up itself and go boom. I've not found descriptions of the fluid like boiling over and coming out the breather...

2) How long do I have until the diff goes boom? I have a track day here in two weeks and I want it to survive at least through that event.

3) Could I have misdiagnosed my issue and the noise is coming from the trans? I think not but I didn't change my trans fluid when I did diff fluid.

I would really appreciate some input on this situation because the search function keeps finding people saying "Just put a diff cooler on it" and "you'll know when it fails because it will go boom". Which is very correct but doesn't help my analysis much.

Thanks!

I appreciate that you covered all the stock responses in your original post. Here's my non-stock response:

Your diff is howling because a werewolf is clearly trapped inside it. Dump the Motul fluid and replace it with silver.

Hope that helps!!

Sent from my SM-G955U using Tapatalk

Quote:

Originally Posted by BettyZ (Post 3870071)

EEjiit

You done had a dirt-dobber or something plug up your vent tube; it built up pressure inside & spewed the lube everywhere :ugh2:

Could potentially be another problem; if you were closer- I’d let you bolt in my pumpkin & take a spin...these diffs are pretty dang strong & take lots of abuse.
Be sure & test drive on known good blacktop, under light,normal & heavy loads...also coasting...also hopefully the biscuits that you put on the ears weren’t too thick/thin & caused a bad pinion angle; that could make trouble as well.
Having the open diff; you can practically put any kinda lube in it...may want to try 85/140 & see if it tames down....no need to use synthetic while troubleshooting.

Since you have an open diff I doubt you overheated it. You'd have to open it up and see what's causing the issue.

When you lost the lube, you probably damaged a bearing or gear. You will need to open the unit and inspect.

OP, your's is about the 3rd or 4th one that I have read that puked fluid out of the vent hose.

How much fluid did you drain out? The stock diff cover holds about 1 liter. Did you drain out less?

Couple of questions. Staying in the same gear. About 50 mph.

1. Is the noise steady state when holding a steady speed?

2. Does the noise increase when you let off the gas?

3. Does the noise increase when you increase the speed?

There is a bunch of these on the net.

https://www.onallcylinders.com/2012/...veline-noises/

Quote:

Originally Posted by Rusty (Post 3870203)

There is a bunch of these on the net.

https://www.onallcylinders.com/2012/...veline-noises/

Whoa, gotta bookmark this one, thx :tiphat:

Thank you for all the tips everyone.

I greatly appreciate your input.

I am unaware of how much fluid I lost, not a whole lot according to how much came out but I didnt measure how much went into the drain pan.

None of the things in the guide posted above describe my situation perfectly. The howl is in all gears all the time.

It does not make noise when the trans/diff is unloaded. The way I would describe it is that the noise goes away when you get off the gas, even if the diff and trans are still spinning. But as the load goes up the noise climbs too. Which is congruent with all of the other behaviors.

Still I don't understand how it puked out the fluid. Is it a joke to say something clogged the breather and it built up pressure and blew it out? Or is that an actual possibility?

I will disassemble the diff some weekend and check it out but I will wait until I get an LSD to put in there so that its worth it. If it blows up before then Oh well.

Again thank you all for your valuable input!

From what I have read in the past. The some diff lubes gets real foamy with lots of abuse and heat. This foamy mix expanse and gets pushed out of the vent breather. If the breather is blocked. Then the lube gets pushed out of the axle seals.

I overheated mine on the tail of the dragon. I did a back to back run and it was done. Diff cooler is on the car now. No dirt dobber nest either. LOL

Quote:

Originally Posted by Rusty (Post 3870795)

Okay I understand, that makes perfect sense thank you sir.

I guess I have found the limit of requiring the Diff Cooler then! I have no problem buying it if I need it. I guess I didn't think that I would overheat the diff. Like yes I saw that it was something that was sold but I didn't consider that driving on the street I would need it.

But I did already buy an oil cooler based on street driving at places like Hocking Hills (mini tail of the dragon) so I suppose that it makes sense that I might overdo the diff there.

Perfect excuse to go LSD, (except thats not really the part that I fried).

Here's a thread on my diff cooler install.

http://www.the370z.com/track-autocro...r-install.html

It doesn't fit with the stock muffler or anything like the stock muffler. If your exhaust is like the FI with twin cans. It will fit.

When I did my install. I also installed a Z1 diff cover and an OS Giken diff. The OS Giken diff uses diff lube that cost about $70 a liter. :shakes head: With the Z1 diff cover and the diff cooler. It takes about 2.5 liters.

With the diff cooler pump and fan off. The highest temp I've seen on my Diff temp gauge was 270F. Turn the pump and fan on. I can watch my diff temps drop to under 200F.

When oil or lube get foamy. They don't lubricate very well. The bearings will lose their lubricating film and run dry. This is what may have happened to you.