Datatek
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According to some stuff I have just read on ZF transmissions the normal oil temperature is 80 to 100C.
transmission cooler
- Thread starter navigator16078
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According to some stuff I have just read on ZF transmissions the normal oil temperature is 80 to 100C.
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- 58,170
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- Preston Lancs.
Ok, i am not bothered about it enough to go into it, so will accept what you say. However I still think it is a bad idea to cool the transmission in this way. Having a part of the radiator with oil running through it has been a successful way of cooling engine oil and transmission fluid for a very long time. This is done by airflow. Having an heat exchanger fed from just about the only place on a radiator that clogs up on a regular basis, on almost every vehicle known to man, at some stage of it's life, is nosensicle in my view. But hey ho cleverer people than me thought of it, so it must be ok. Seems like a built in fail point to me. Many P38s fail because the owners from new or the subsiquent owners could not afford the expensive mainenance they require. So it was scimped. The great spirit alone knows what the L322 is going to be like in twenty years time. A bloody nightmare i would predict.
Datatek
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I absolutely agree with what you say. Having read the MB problems I think I would mod the cooling and fit a separate cooler before the rad failed.
Bemble
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Automatic transmissions with torque converters fitted with lock-up clutches produce the majority of their heat load at low vehicle speeds, where air flow is at its minimum.
Water has both a higher thermal conductivity and a higher specific heat capacity than air and therefore requires a lower volumetric flow to shift a given heat load. An oil-to-water cooler also acts as a transmission fluid heater at low ambient temperatures as the engine coolant gets up to temperature much more quickly.
An oil-to-water cooler is therefore much more efficient than an oil-to-air one.
The main disadvantage is cost and, as has already been mentioned, the risk of cross-contamination of fluids.
The L322 Range Rover transmissions are filled for life (= 10 years) and as the life of a transmission fluid at elevated temperatures is halved for every 10 deg.C increase in temperature it is critical that the fluid temperature is kept within limits. The transmissions are therefore fitted with a bulk oil temperature sensor and if this detects fluid temperatures above 138 deg. C the transmission ECU will inhibit upshifts to keep the engine speed high and hence maintain high pump speeds & therefore fluid flow through the cooler.
As has already been stated, bulk oil temperatures of 85-95 deg.C are normal for automatic transmissions.
Water has both a higher thermal conductivity and a higher specific heat capacity than air and therefore requires a lower volumetric flow to shift a given heat load. An oil-to-water cooler also acts as a transmission fluid heater at low ambient temperatures as the engine coolant gets up to temperature much more quickly.
An oil-to-water cooler is therefore much more efficient than an oil-to-air one.
The main disadvantage is cost and, as has already been mentioned, the risk of cross-contamination of fluids.
The L322 Range Rover transmissions are filled for life (= 10 years) and as the life of a transmission fluid at elevated temperatures is halved for every 10 deg.C increase in temperature it is critical that the fluid temperature is kept within limits. The transmissions are therefore fitted with a bulk oil temperature sensor and if this detects fluid temperatures above 138 deg. C the transmission ECU will inhibit upshifts to keep the engine speed high and hence maintain high pump speeds & therefore fluid flow through the cooler.
As has already been stated, bulk oil temperatures of 85-95 deg.C are normal for automatic transmissions.
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After all is said and done, i still think it is a stupid idea to put the feed for the heat exchanger in the only place in the rad that is almost guaranteed to block up. As you said earlier it is a common fault on the L322, a built in common fault and bad design in my view.
Bemble
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Agreed.
Because the 'bottom hose' is above the level of the eight rows reserved for the transmission fluid cooler it means that it's not possible to flush this part of the radiator and therefore the radiator has to be replaced if it gets bunged up by sediment.
Fortunately when I changed mine an OEM (Behr/Hella) radiator cost less than £170 and it's a piece of cake to fit (quick release hoses, etc.)
Because the 'bottom hose' is above the level of the eight rows reserved for the transmission fluid cooler it means that it's not possible to flush this part of the radiator and therefore the radiator has to be replaced if it gets bunged up by sediment.
Fortunately when I changed mine an OEM (Behr/Hella) radiator cost less than £170 and it's a piece of cake to fit (quick release hoses, etc.)
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It's good to know that their bad design only costs £170.00 and is a piece of **** to fit. Maybe the introduction a couple of flushing plugs would make a difference and then you could flush the rad.
As i said bad design.
