What is your regular diff oil temp? (Mach 1 only)

[murick]

I had the whole differential replaced due to a whine and clunk two months ago. It solved the whine, but not the clunk. Now, I believe, I am seeing elevated diff oil temps compared to what I was used to. So I thought I might ask here, to get a better idea.

Few things to keep in mind though:

1. I am reading the temps on the dashboard "analogue" gauge (which can be turned on among the others). I am used to having this three there: diff oil temp, cylinder head temp, and engine oil pressure.
2. The oil temp gauge is marked only at min and max values, which are 50°C and 175°C respectively here in metric world (which would correspond to 122°F and 347°F). Any other value I have to eyeball, but for some reason the "normal" values aligned quite nicely with 25°C increments which are emphasised on the gauge (75°C, 100°, 125°C and 150°C) so the eyeballing is not that hard.
3. I do not know what would be the value in Fahrenheit, but I would expect it would be the same scale/temps just using a different metric.
4. I expect that the ambient air temp would have an impact.
5. The driving style is a factor too (spirited, street, highway, cruise).
6. The (average) speed could also have an impact.

My (elevated) example: highway cruise, 150-160 km/h, (90-100 mph), ambient temp 20°C (68°F), diff oil temp 100°C (212°F)
Just to give a perspective a CHT at the same time was 80°C (176°F).
Before at the similar conditions I was used to 75°C (167°F) oil temp and a much longer time to reach that value.
Now it seems the temp is 25°C higher and also raises faster.

I wonder if the fact the diff is new may also play into that, unfortunately I do not remember what were the temps when the car was new.
The fact the this heats up so much concerns me also because it could be a defect or some additional friction on anything in the housing (could be a pinion-ring wheel, the diff itself, spline bushings, etc.)
I also thought about a possibility the shop did not fill the housing with the right oil, or the right amount, etc. There is a step when filling the oil, one should run the pump for 2 minutes and then check and eventually top the fill again.

So, lot of variables and potential pitfalls, but I hope having some ballpark values could be useful anyway.

Last note: Please reply only with Mach 1 values. I believe regular GT does not have the pump and the radiator, and GT350 may be tuned differently.

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[Skye]

2022 Mach w/Tremec. I monitor diff temp, CHT and oil pressure.

Differential Gauge: mine reads from 100 - 350 F / 37 - 176 C.

Differential Temperature, warmed and stable: 150 - 160 F / 65 -71 C.

CHT: 190 - 200 F / 87 - 93 C while driving, depending on speed and ambient temperature. Idling at a stoplight, temperatures will reach 215 F / 101 C, at which time the fans will engage. The hottest I've seen the car is about 220 F / 104 C, often when starting off from a light or brief stop/shutdown.

Oil Pressure: idling, A/C on with a hot day, no lower than 15 - 17 psi / 1 - 1.17 bar. I have not installed an oil temperature gauge.

Earlier this year, I had a half shaft seal in the diff replaced. Since they were going to have bits disassembled I asked them to perform a service on the diff, to replace the oil. Everything went as expected.

I noticed on the receipt they did install Ford's friction modifier. Torsen has said in their blogs that, while the modifier is not required, it is OK to use, for reduced NVH. Since the diff has been serviced, I feel it's slower to come up to temps, operates about 10 F / 5 C cooler than before. We're in Summer now. The hottest I've seen it is about 160 F / 71 C.

Having the car since new, the hottest ever I remember seeing my diff is maybe 175 F / 80 C. This would be on a hot day, stressing, but not beating on the car.

Returning to your concerns, you figure a drivetrain component like that will take as much as 1,000 mi / 1,600 km to weather in. In the mean time, the repair work is under warranty. Maybe return and ask them to check the level again? Could be some air pockets in the cooler or something have now worked their way through. Maybe something like that. If anything, it'd remove one variable/doubt, allowing you to continue to monitor other aspects of the repair.

 

[Autojvnkie]

Regular street and highway driving typically results in a differential oil temperature ranging from 170°F to 215°F. During extended or spirited canyon runs, it's common to see it climb to 225°F to 235°F

If the car is hitting sustained temperatures over 240°F - 250°F on a road course, it indicates hard track use where the factory differential cooler will actively engage

 

[murick]

@Skye
Thanks for the comprehensive reply!

Your observations almost perfectly match mines (including the CHT) before the diff replacement. Despite few track sessions in a quite hot weather last summer I do not think I ever saw the diff oil temp reaching 100°C (212°F).

Now, inspired by @Autojvnkie reply, do we know when the pump engages on Mach 1? And if the pump does not engage, is the radiator even doing anything? If this would be the case, and your temps (and mine before the diff change) were low enough to get cooled passively, then the problem would not be the pump, but something in the diff that generates much more heat than before.

The friction modifier you mention I believe is a fluid added to the mix, but even if I had it before (in the factory filling) and the shop did not add it now, the temp difference you observed does not correspond to my increase, which looks like 25°C (~50°F).

The last thing that comes to mind. The one or the reasons for replacing the diff was a loud clunk together with forward-backward sway observed when shifting. One hypothesis I am looking into right now is that it is a manifestation of loose "differential backlash". Interestingly the clunk seems to be more pronounced after the diff change.
So I wonder, if they adjusted it correctly (if it is supposed to be adjusted on a new part at all) and that could lead to the heat build-up. This is however countered by the fact that the original diff had almost same clunk and did not heat as much.

 

[Skye]

...do we know when the pump engages on Mach 1? And if the pump does not engage, is the radiator even doing anything?

I looked at a document I have (screenshot attached). IDK what temperature the fan kicks in. "Predetermined temperature", which is programmed into the Powertrain Control Module. The document is for GT500s as well as Machs and others. It does reference overheating, and when the PCM will throw a code.

Airflow from the rear aero assembly will keep fluid in the radiator cool, like in a water radiator when the thermostat is closed. The excess fluid heat from the diff will flow in the direction of the cooler. But I'd think any cooling effect would be limited. Like a water radiator, the medium (gear oil), needs to circulate, yes.

I don't remember a Mach with a diff pump failure and the characteristics of that. A GT350 thread would be a great proxy. I'd need to search.

The last thing that comes to mind. The one or the reasons for replacing the diff was a loud clunk together with forward-backward sway observed when shifting.

Another document relates to t-shooting clunks, grinding and howls. "Clunks" and those problems came down to three general areas:

- Gear lash (including "ring gear backlash")
- Fluid level
- Pinion front bearing failure

I can see a dealer replacing the entire differential. All one unit. That makes sense. Why you'd continue to experience the clunk I cannot offer more ideas. Could be the fluid level, which we were already concerned about. But I feel fluid alone is a bit of a stretch.

It's another reason to return and discuss. Simply get it on the lift, have them check the fluid, connections and all that while up. I think we've all caught a few things from time-to-time of missed connectors, low fluid, loose bolt, etc. Then continue to monitor for changes.

Edit,

Similar question, but no answer.

The Tremec's fluid circulates via a series of gears. When the assembly is spinning, the gears do, and pump the fluid through that radiator.

https://www.mustang6g.com/forums/th...riggers-the-differential-pump-come-on.114957/

 

[murick]

I looked at a document I have (screenshot attached). IDK what temperature the fan kicks in. "Predetermined temperature", which is programmed into the Powertrain Control Module. The document is for GT500s as well as Machs and others. It does reference overheating, and when the PCM will throw a code.

I found this part in my shady service manual too. Over 145°C writes a permanent DTC, but what is the one predetermined level and the other predetermined level is a mystery .

I don't remember a Mach with a diff pump failure and the characteristics of that. A GT350 thread would be a great proxy. I'd need to search.

Unless the failing pump is an unfortunate byproduct of the diff replacement, I do not see, why it would fail.

I can see a dealer replacing the entire differential. All one unit. That makes sense. Why you'd continue to experience the clunk I cannot offer more ideas. Could be the fluid level, which we were already concerned about. But I feel fluid alone is a bit of a stretch.

I agree. The fluid level may impact the temperature, but the clunk is something else. It appeared "from nothing" after I added Steeda Ultimate stop the hop kit and differential bushings. Though I do not think the mods caused that, but rather the mods caused it to be more pronounced, by tightening the diff and rear suspension, so the system had suddenly much less leeway to absorb it.

Similar question, but no answer.

The Tremec's fluid circulates via a series of gears. When the assembly is spinning, the gears do, and pump the fluid through that radiator.

Right. When changing the oil in Tremec, one is supposed to run the transmission in neutral for some time (again to fill the radiator and the external circuit) and then check and top the filling again.
But for the diff, the manual says, run the pump for 2 minutes using a diagnostic tool...

I have just planned a check at the shop, unfortunately, in one month.

 

[WD Pro]

Yeah I know, GT owner, but ...

Steering clear of any talk of temp, something you may be interested in ref the friction modifier, and what may / may not be included in the workshop manual in your country for the 'euro' :

https://www.mustang6g.com/forums/threads/euro-cars-diff-oil-change-advice-experiences.186902/

Ignore my post #4 as it may not make sense - it was a (polite) response to post #3, which if I recall correctly, was likely a response to my forum stalker (since banned, with posts removed) ... lol

WD

 

[murick]

Yeah I know, GT owner, but ...

Steering clear of any talk of temp, something you may be interested in ref the friction modifier, and what may / may not be included in the workshop manual in your country for the 'euro' :

https://www.mustang6g.com/forums/threads/euro-cars-diff-oil-change-advice-experiences.186902/

Ignore my post #4 as it may not make sense - it was a (polite) response to post #3, which if I recall correctly, was likely a response to my forum stalker (since banned, with posts removed) ... lol

WD

Thanks for pointing it out, even as a GT owner ! I will definitely look into it.
My shady service manual says (no idea if it applies to Euro version, but it should apply to my VIN).

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