overheating transfer case

bemax · Aug 29, 2024

This morning I drove about 15 - 20 minutes at max. speed (160 km/h or 100 mph). Outside temperature at that time has been around 22 degrees Celsius.
I then got a warning "motor oil level low" (yellow warning)
I reduced speed significantly and had a look at the "offroad temperature" screen. This showed a transfer case temperature of 115 degrees Celsius which was outlined in yellow.
Motor temperature and gear box where at 95 and 78 degrees by than.
The temperature of the transfer case dropped fast at the speed of 120 km/h and the yellow outline vanished after a minute. After 10 or 15 minutes the warning "motor oil level low" vanished as well and the yellow triangle disapeared.
Has someone else had this Problem before?
To me it looks like the transfer case cooling system fails at a certain speed.

I do not want to start a discussion whether or not someone should drive at this speed over a longer period, as the speed is allowed in Germany and the motor turns only 3000 rpm at that speed. Of course it is in many ways more intelligent to drive slower.

Tom D · Aug 29, 2024

You're a brave man!
Interesting that 115 degrees is only an amber warning.

TD5-90 · Aug 29, 2024

bemax said:
This morning I drove about 15 - 20 minutes at max. speed (160 km/h or 100 mph). Outside temperature at that time has been around 22 degrees Celsius.
I then got a warning "motor oil level low" (yellow warning)
I reduced speed significantly and had a look at the "offroad temperature" screen. This showed a transfer case temperature of 115 degrees Celsius which was outlined in yellow.
Motor temperature and gear box where at 95 and 78 degrees by than.
The temperature of the transfer case dropped fast at the speed of 120 km/h and the yellow outline vanished after a minute. After 10 or 15 minutes the warning "motor oil level low" vanished as well and the yellow triangle disapeared.
Has someone else had this Problem before?
To me it looks like the transfer case cooling system fails at a certain speed.

Doing longer Autobahn high speed driving regularly. Always with a close eye on xfer case temp. It's easy to exceed 100°C if you're not careful. For myself I limit speed to a max of 90°C. Which is approximately max 140km/h during summer days.
I never exceeded the 115°C limit, didn't know there was one before your post. I try to drive reasonably...

In fact, I was wondering too how such temperatures are possible, with the additional oil cooler in the bumper, which should be reasonably effective at higher speeds. Checked oil level and oil colour twice (17000kms on the odo): Obviously everything ok. I must admit though that till now I didn't do deeper research like oil cooler inlet & outlet temp etc.
Like you, I observed that the temp relatively quickly goes down again if you drive slower for a couple of minutes. This suggests that oil circulation through the cooler basically works, I doubt that heat dissipation through the xfer case housing only would be so effective. Anyway, the obvious poor efficiency of the xfer case wasn't something I would have expected from a new design.

I'm about due for first service (display says 100+ days overdue, but I took delivery end of August last year). I'll bring this topic up when I hand the car in.

bemax said:
I do not want to start a discussion whether or not someone should drive at this speed over a longer period, as the speed is allowed in Germany and the motor turns only 3000 rpm at that speed. Of course it is in many ways more intelligent to drive slower.

Full ack. Even more: There's absolutely no reason to apologise if you drive faster sometimes (or often). As there's no reason to apologise for driving slowly. Unless you're driving in front of me ;-)

emax · Aug 29, 2024

bemax said:
To me it looks like the transfer case cooling system fails at a certain speed.

Let's call it "at a certain load".

The Autobahn drive was imo a good test of the transfer case at higher loads. Imagine an off road afternoon in rough terrain at 30°C, say, in Sardinia or any other southern country.

To me, your experience seems to confirm what @AWo already mentioned a number of times. The cooling system of the Grenadier is too weak at high temperatures and loads.

That's at least what I remember.

Area 51 · Aug 29, 2024

Wowzers, great posting and great information.

TD5-90 · Aug 29, 2024

emax said:
Let's call it "at a certain load".

The Autobahn drive was imo a good test of the transfer case at higher loads. Imagine an off road afternoon in rough terrain at 30°C, say, in Sardinia or any other southern country.

To me, your experience seems to confirm what @AWo already mentioned a number of times. The cooling system of the Grenadier is too weak at high temperatures and loads.

That's at least what I remember.

I don't think the cooling system is generally wrongly designed/dimensioned. It's a heavy, powerful machine with the corresponding power losses. The vehicle gives you more information on its operating conditions than the average vehicle. This is one thing I found very cool about the Grenadier from the beginning. Now the question is: What do I do with this information as a driver?

The offroad/temperature screen is my default and favourite screen when I'm driving. Besides the obvious information, you can e.g. see when a DPF regen is in progress when there is a sudden increase in engine oil temp to >110°C when even under high load the normal engine oil temp is ~90...95.
I like to know what's going on. But I've heard of other mindsets ;-)

Regarding the transfer case, I actually did expect it to be more efficient than e.g. that of the Defender TD5. After Autobahn drive with my TD5 (235/85/16) at 120-130 at a warm day, xfer case temp is somewhat around 90°C (measured with thermal camera). Without oil cooler. The required power should be approximately the same as with the Grenadier due to the similar air resistance (at high speeds the primary contributor to power demand). So, the xfer cases appear to be similarly efficient. In the Defender, I use some Liqui Moly additives, maybe this helps. I did not try this in the Grenadier so far.

Going 140-160 with the Grenadier exponentially increases both power demand and xfer case losses, so I think everything is as to be expected. Unless the newly designed xfer case would be significantly more efficient than a design out of the 70s. Which is indeed what I would have expected.

AWo · Aug 29, 2024

It is not the engine or cooling design...it is the grille with the lights which prevents enough air reaching the cooler. That's why there is an auxilliary cooler in the bumper.

Gearboxes are often prone to overheating. Bad position for cooling behind the engine. That's why there is often an external oil cooler. That is the other cooler in the bumper. You could mitigate that with more oil and a larger sump, but space is rare...and you need to keep a low underbody profile.

AWo

Tazzieman · Aug 29, 2024

I'll be interested to see how regular autobahn drivers fare when their TC oil is changed/ inspected. I''m a fan of driving with the gear oil temp gauge screen showing , esp when towing uphill on hot days.

emax · Aug 29, 2024

I have the temperature display always on when I start the car and the engine is still not on operating temperature. When I drive longer legs, I also switch it on - on the Autobahn as well as in cities in the rush hour.

It is interesting to see how the temperatures behave and one interesting finding was that, for example, the engine oil temperature does not only depend on the load that the engine has to withstand. It is often the case that this drops from over 100°C to 95°C when the power requirement is higher - due to higher revs which cause higher oil flow.

Not only the required power but also the oil flow and the number of revolutions together with the airflow build a complex control loop.

Clark Kent · Aug 30, 2024

AWo said:
It is not the engine or cooling design...it is the grille with the lights which prevents enough air reaching the cooler. That's why there is an auxilliary cooler in the bumper.

Gearboxes are often prone to overheating. Bad position for cooling behind the engine. That's why there is often an external oil cooler. Thst is the other cooler in the bumper. You could mitigate that with more oil and a larger sump, but space is rare...and you need to keep a low underbody profile.

AWo

Great stuff @AWo.

The transfer case oil cooler (left side) has a clear inlet and a duct that guides onto the face of the cooler. All air that enters the cooler compartment has to pass through the cooler to escape. There is no alternate airpath. Great for low speed and off-road.
At high speeds the cooler matrix will create a minor choke point with a corresponding increase in compartment air pressure and reduced air velocity across the cooler. This means more heat stays in the cooler. Combined with the power dissipation requirements of sustained high speeds, this might be enough to overwhelm the cooling system.

NQ94 · Aug 30, 2024

It would be intersting to view the specifications from Tremec on t/case duty cycle and continuous high speed operation. The t/case overheating at high speed does not seem to be a design fault but a design limitation. Even with a cooler there is not much oil in the t/case and eventually it will be heatsoaked enough that a cooler will become ineffective.
Not beeing Ineos specific I was always curious how hot full gear driven transfer cases with like, LR 110 and Land Cruiser designs (very similar to Tremec's design) get while heavy towing and operating with massively increased GVM modifications and big tyres (Toyota LC79) as most do not monitor t/case temperatures, do not have coolers and only have one to two litres of oil capacity.

landmannnn · Aug 30, 2024

For most of my life I have been blissfully unaware of tyre temperature, transmission temperature, diff temperature etcetera with just a vague gauge giving engine coolant temperature.
Now I have many more things to worry about.

TD5-90 · Aug 30, 2024

Clark Kent said:
...
The transfer case oil cooler (left side) has a clear inlet and a duct that guides onto the face of the cooler. All air that enters the cooler compartment has to pass through the cooler to escape. There is no alternate airpath. Great for low speed and off-road.
At high speeds the cooler matrix will create a minor choke point with a corresponding increase in compartment air pressure and reduced air velocity across the cooler. This means more heat stays in the cooler. Combined with the power dissipation requirements of sustained high speeds, this might be enough to overwhelm the cooling system.

I see you point. Qualitatively, this sounds reasonable to me.
Is it possible to easily judge from simply looking at an arrangement what the critical speed for choking would be?

TD5-90 · Aug 30, 2024

landmannnn said:
For most of my life I have been blissfully unaware of tyre temperature, transmission temperature, diff temperature etcetera with just a vague gauge giving engine coolant temperature.
Now I have many more things to worry about.

I think you shouldn't be worried. Use the additional information to your advantage. Looking at other 4x4 forums, gearbox and axle temperatures are always a point worth looking at, even if the vehicles don't tell you anything about them in stock configuration. Lots of aftermarket oil temp sensors and coolers out there, sometimes for good reasons...

NQ94 · Aug 30, 2024

landmannnn said:
For most of my life I have been blissfully unaware of tyre temperature, transmission temperature, diff temperature etcetera with just a vague gauge giving engine coolant temperature.
Now I have many more things to worry about.

That is the reason most of these features were never fitted to cars. Most drivers a car is an appliance and don't know a how car works let alone understand what most of the warnings are for.

rovie · Aug 30, 2024

landmannnn said:
For most of my life I have been blissfully unaware of tyre temperature, transmission temperature, diff temperature etcetera with just a vague gauge giving engine coolant temperature.
Now I have many more things to worry about.

No, you don't have to. I've been driving off-road vehicles exclusively for more than 25 years. And I work with them too. By that I mean trailer operation. Both on muddy meadows and on motorways. And the trailer doesn't just carry compost waste, but also machines and sometimes 1600 kg of live stock.
Apart from the correct tyre pressure and looking at the engine oil temperature, I've never needed anything else and I don't use this overabundance of information on the Grenadier. None of my previous vehicles have been damaged or displayed error messages as a result. I expect the same from the Grenadier.
And by the way, I would never think of driving 160 hours/km with the Grenadier.

NQ94 · Aug 30, 2024

Probe

rovie said:
No, you don't have to. I've been driving off-road vehicles exclusively for more than 25 years. And I work with them too. By that I mean trailer operation. Both on muddy meadows and on motorways. And the trailer doesn't just carry compost waste, but also machines and sometimes 1600 kg of live stock.
Apart from the correct tyre pressure and looking at the engine oil temperature, I've never needed anything else and I don't use this overabundance of information on the Grenadier. None of my previous vehicles have been damaged or displayed error messages as a result. I expect the same from the Grenadier.
And by the way, I would never think of driving 160 hours/km with the Grenadier.

Powertrain temperatures are likely not a major issue in Europe when towing unlike Australia where every one seems to want and a 3.5t vehicle to have a massive GVM & GCM upgrades and do towing jobs better suited to a prime mover while not understanding the knock on effects it has on a car.

rovie · Aug 30, 2024

NQ94 said:
Probe
Powertrain temperatures are likely not a major issue in Europe when towing unlike Australia where every one seems to want and a 3.5t vehicle to have a massive GVM & GCM upgrades and do towing jobs better suited to a prime mover while not understanding the knock on effects it has on a car.

Yes, I can understand that. I think you also have completely different environmental conditions. These information may be helpful for you.

Clark Kent · Aug 30, 2024

TD5-90 said:
I see you point. Qualitatively, this sounds reasonable to me.
Is it possible to easily judge from simply looking at an arrangement what the critical speed for choking would be?

Good question @TD5-90

Not without testing and number crunching. Too many variables. I offered this as a contributing factor but it's not the primary problem. The cooling system has a heat dissipation rating and will be effective provided the vehicle is operated within limits. Maintaining normal temperatures while blasting down the autobahn probably wasn't a top test and evaluation criteria.

This article from the electronics industry talks about how fans, ventilation openings and enclosure designs affect mass airflow rates which are necessary for good heat dissipation. Check it out if you're having trouble falling asleep.

Remember when Clarkson struggled with airflow?

Trialmaster · Aug 30, 2024

No surprises. Suggest you drive a little longer at VMO to see how long the Transfer Box holds up - just curious!

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