Weird vibration when differential is cold - have you experienced that?

[Rhyanski]

Hi guys,
Today in the morning I had to leave earlier than usual. Temperature outside was 2 degrees Celsius. Engine was in nominal temperature, and I've driven the car for a kilometer or so, so both tires and differential were still cold. I was driving in the range 60-80kmh and I've heard a noise similar to the exhaust note when running at around 4000rpm. I was surprised to see the engine running 5th gear and RPM being around 1500. While still moving with 80kmh, I switched to neutral (manual gearbox) so the RPM dropped to around 700, but the noise persisted.
Pressing the brake - reduced it, acceleration increased the noise.
So, if I drive within the city limit (up to 50kmh) I don't have the vibration, but riding on the high-speed lanes with speed between 60 and 80kmh, I get the vibration. Above 80kmh, it starts reducing gradually.

After like 20 minutes - no more vibration and strange noise anymore, so I guess something warmed up.
I have driven the car several times today and there's no such issue anymore, happened only in the morning after the car has spent like 15h in the garage without moving.

Now, my best guess is that the rear diff was still cold, however this vibration to the extent of mistaking it for exhaust rumble is weird.

My questions and concerns here would be :

1. How can I check the diff oil level?
2. There are no weird lights on the dash lit, but the diff temp was flat bottom on the gauges, actually diff temperature raises only after long drives on high speed. Where's the sensor for the diff temperature?
3. Has anyone experienced similar behavior when the car is still cold?

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[WD Pro]

Your diff will be a trac loc so you are in the minority asking this question in the M1 section (you might be better / have a bigger audience in the general or transmission sections - and make sure to quote it’s a trac loc).

Stick your head under the back - it’s easy to see the fill plug and temp sensor looking from the rear of the car.

They take a while to warm up under normal driving - add torque and make the diff work a little and it will warm up much quicker.

I can’t help with your issue sorry, but I hope you get it sorted

WD

 

[Skye]

While I have operated in those temperatures, I do have a Torsen diff. FWIW, I have not had issues.

 

[Rhyanski]

Your diff will be a trac loc so you are in the minority asking this question in the M1 section (you might be better / have a bigger audience in the general or transmission sections - and make sure to quote it’s a trac loc).

Stick your head under the back - it’s easy to see the fill plug and temp sensor looking from the rear of the car.

They take a while to warm up under normal driving - add torque and make the diff work a little and it will warm up much quicker.

I can’t help with your issue sorry, but I hope you get it sorted

WD

Yeah, true, mine is EU speck as well, so not a torsen diff.

I will check at the back, reason for asking is I had some thoughts sensor may not be on the diff, but on the oil cooler for the diff oil cooling system. Does not make much sense now, but I guess if there was insufficient oil in the diff / diff cooling systems, the diff temp gauge on the dash would show higher temps very fast...

Indeed in the last couple of days I was very vigilant whether I'd hear that noise again, but happily I may say I don't... We'll see...

 

[WD Pro]

Sensor is in the same place (near the bottom, slightly offset to the left), with or without the OE diff cooling

WD

 

[luca1290]

To check the level just open the upper plug with a 3/4 inch tool.
Oil should dribble out or you must be able to feel it with your finger just below the opening.

Remember to raise the car leveled straight, that's all for checking.

For the noise, differential or maybe a wheel bushing. Does the noise increase if you put a little load on it? (steer the car left or right while moving to load the same side).
Can you raise the car and shake / rotate the wheels?

 

[RoGCobraRV]

I had this problem when car was riding on its stock tires for about 10 mins when driving in the cold. Ever since I changed my wheel/tire setup it is gone. So imo it's a tire issue or at least it was for me.

 

[WD Pro]

To check the level just open the upper plug with a 3/4 inch tool.
Oil should dribble out or you must be able to feel it with your finger just below the opening.

You need a 3/8 square drive (standard ratchet wrench will fit right in) for the fill plug and the level is within 9mm of the fill plug (WTF Ford …)

I had heard a rumour that filling them level could lead to some being expelled through the breather or have a greater chance of seal leakage - not sure how true that is though ?

WD

 

[Rhyanski]

I had this problem when car was riding on its stock tires for about 10 mins when driving in the cold. Ever since I changed my wheel/tire setup it is gone. So imo it's a tire issue or at least it was for me.

Yeah, I'd initially think so as well, but I haven't changed tires and the noise is gone. Definitely after warming-up, I don't have issues. And, this was the first time ever this 'noise' occurred. Never before, never again.

I'll try checking out the level via the fill plug.

 

[murick]

@Rhyanski
Now while reading what @RoGCobraRV wrote, which tires did you have and at which pressure?

I remember once I had some strange vibrations from rear and after some thinking decided it was the tires (the original summer PS4S) being parked in a cold weather and being under inflated (~ 2.0 bar), probably got deformed from sitting still and did not "reform" fast enough in this weather.

 

[luca1290]

You need a 3/8 square drive (standard ratchet wrench will fit right in) for the fill plug and the level is within 9mm of the fill plug (WTF Ford …)

Yeah, sorry, 3/8. Got my inches messed up today.

Your procedure is WSM-level perfect . "Fill it with the finger" is the more bread and ham approach tough. It will definitely not vent out unless you are filling it with the nose of the car pointing downward, there is plenty of room for it to expand.

 

[Rhyanski]

@Rhyanski
Now while reading what @RoGCobraRV wrote, which tires did you have and at which pressure?

I remember once I had some strange vibrations from rear and after some thinking decided it was the tires (the original summer PS4S) being parked in a cold weather and being under inflated (~ 2.0 bar), probably got deformed from sitting still and did not "reform" fast enough in this weather.

Not the stock, I'm still running the winter tires - Goodyear UltraGrip Performance +, and never had an issue till now... TO be honest, I haven't driven above 50kmh in the cold this year,as we always have the traffic, but the other day there were very few cars on the road (6:45a.m.) and I went with the speed limit.

Another thing is that I haven't felt the vibration, I've heard it. The steering was normal, there was no vibration in the chassis whatsoever, I've heard it as if I was going like 4000rpm and it sounded like the exhaust note. I looked at the dash - it said 1600, so I just moved to neutral and the thing persisted. Pressing the brakes and going down to 50, everything went back to normal. Going back with the trottle - from 50 to 80kmh the sound was increasing, then after 80 started going quieter(maybe a little bit higher pitched, I guess). For sure there was no instability in the car, or lack of power or anything disturbing... quite weird.

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