Auto transmission oil temperature.

iana · Guru

Auto transmission oil temperature.

Radar · Guru

iana wrote:
Anyone know what the operating temperatures for synthetic transmission oil is, I can find info on the mineral oil but not the top end temperatures for synthetic. Funny enough they publish the minimum temperatures, but not operating and max. My guess is 104 degrees Celsius.

Funny enough I was down at a Independent Automatic specialist just the other day and the man went to great lengths to show me the well used chart with operating temps high and lows of all oils suitable for various makers of transmision.

I can not be 100% certain but it was something like that before the oil breaks down.

I was looking for ways to add longevity to my Nissan 7 speed auto, we have the oil change at 40 000 kilometres after having the oil changed the other day at my regular servis place and learning they can only drain 50% of the oil out, we may go on to every 20 000 ks as sub $200 cost is here or there and we do plan to keep it for a while yet, the car is now 6 years old, 130 000 with about 73% towing the 2.7 tonne caravan.

Possum3 · Guru

Transmission fluids seem to be an array of witches brews with some being developed for particular transmissions - and replacing a portion of it places you in the predicament of not being able to mix another type ( a problem I had with Rolls Royce that was still using mineral oils). Additives are available - but which one is best suited for your fluid you need to know properties of existing fluid.
Perhaps there is someone on here that can better advise regarding the chemical side. What I do know is as Sol said all those years ago "Oils ain't oils".

iana · Guru

My transmission is operating at about 105-107 degrees, the oil passed the last service inspection, so now headed for 20,000km. I would like to fit a fan assisted cooler, but the thermostat switches are I think all set for mineral oil. I have found one switch that sets at 100 degrees, but that may also be too low. This is work in progress with not much advance.

yobarr · Guru

iana wrote:
Anyone know what the operating temperatures for synthetic transmission oil is, I can find info on the mineral oil but not the top end temperatures for synthetic. Funny enough they publish the minimum temperatures, but not operating and max. My guess is 104 degrees Celsius.

Whilst I know little about transmission oils,my good friend,Mr Google,advises that the optimum operating temperature for synthetic transmission oil is 80 degrees centigrade,but up to 108 degrees centigrade is acceptable.Hope this helps? Cheers

Aus-Kiwi · Guru

About the same as coolant or engine temps . As its cooled. Or heated from
Engines coolant . (80 to 100*c) Maybe spike higher for short time ? We spoke to a tech at ZF auto trans . He said autos run fine if run cooler . Keeping in mind some vehicles go through half their life hardly getting to full on high temps . Short trips of taking kids to school etc .

Jaahn · Guru

yobarr wrote:
iana wrote:
Anyone know what the operating temperatures for synthetic transmission oil is, I can find info on the mineral oil but not the top end temperatures for synthetic. Funny enough they publish the minimum temperatures, but not operating and max. My guess is 104 degrees Celsius.
Whilst I know little about transmission oils,my good friend,Mr Google,advises that the optimum operating temperature for synthetic transmission oil is 80 degrees centigrade,but up to 108 degrees centigrade is acceptable.Hope this helps? Cheers

Hi smile

I can tell you that some(all) sealed for life transmissions have an oil life calculator program in the ECU that measures the temperature of the oil and time at each temperature and stores it as a number score. So when the number gets to a specified point it 'says' change the oil with a check light and code ! even in the sealed for life transmissions.

So that shows you the higher temperatures are considered bad for the oil life. This is well known and is why coolers have always been recommended. In this country the initial heating of the oil is not necessary or wanted for normal work. IMHO.

Jaahn

Old and Grey · Senior Member

Hi Iana,

Well i'm no expert either. However I do know that Penrite Full Synthetic LV that have used at every change boils 47deg higher then the Toyota mineral oil they use in their 200 series Landcruisers.

I do my own 200 servicing TOTAL. Would not let Toyota near my Truck. Sealed for life, Oh come on.

Only thing missing is the dip stick. Still has the drain plug and over flow plug and the fill plug.

I have completed four changes in 150,000km. I flush the cooler and lines. as well ONLY with LV.

Toyota Flush out the cooler with mineral based %#*^#@.

The only thing is they don't tell you is, That stuff can't be removed 100%. Which leaves it to break the properties of the new fluid from the start.

Drain the old, Flush with new, and refill with the new.

Costs me Less then $100 each time. buying the LV when on sale at 40% Off.

To do it your self 1 x 12v transfer pump $36 Evil Bay. 2 x 5lt Jugs $52 off Evil Bay 2mtrs of 10mm clear tubing.

Very easy to do. Go to U Tube and have a go. Oil Is cheap, and I won't scrimp on oil.

Sorry for getting off track iana.

Grey

-- Edited by Old and Grey on Saturday 18th of July 2020 03:13:38 PM

swamp · Senior Member

HI
ALL OIL is Specified for running under 100 deg cel . Oil temp over 100 deg degrades additive packages ALWAYS . Synthetics just last a little longer but still have limits .
The above comes from oil companies !!!!

So synthetics are a good idea providing they are TRUE synthetics eg 100% manmade and no mineral base stocks .

Transmissions degrade internal plastics ,orings ,wiring etc by running at hotter temp 100+,,, 80-90 ideal ,,70-100 ok
Good transmissions donot run at high temps
Eg many many quality transmission places fit a dual cooler and remove/bypass high temp thermostat to Rangers [110cel down to 90deg cel ]
If Ford did care which is a joke these transmissions would have the thermostat removed !!!!!!!!!!!!

Verify running temp first

DONOT listen to the dealers when they say the auto trans temp alarm goes of at 110--130c
For comparison some brands say up to 120cel is ok for engine ,,when the alarm goes off
Do both of the above often and your vehicle will breakdown and have an early death guaranteed !!!!!!!!!

-- Edited by swamp on Saturday 18th of July 2020 03:27:47 PM

Aus-Kiwi · Guru

Trans temps being heated is about economy on short trips . More to pass EPA nothing to do with durability . Dealers will NOT admit to any issues in their products . Had this over the years with suspension bushes on electrical work trucks .

iana · Guru

The engine coolant thermostat will be open at 90 degrees, and with the plate heat exchanger back to back with the auto transmission oil, I would say about 95 degrees is min operating temperature, and I notice that the top end viscosity figures for the oil is 100 degrees given in the specs by the oil manufacturers. So I am thinking those are the limits the vehicle manufacturer had in mind. I am not saying that is correct, just that, that is what the manufacturer finds acceptable. Still am unable to find the high end of temperatures for synthetic oils on the net as to what is good or bad. I don't take any notice of info put out by those whose only interest is selling transmission coolers.

swamp · Senior Member

Hi
Fitted plenty of oil coolers in my time to engines/ transmissions and hydraulics . Plus heat exchangers to airconditioning .
Many engines built by third party then fitted to some makers chassis have there sump size reduced .This tortures oil and shortens its life . To add to the pain often the chassis maker will have a longer service interval WTF !!!!!!!
Hydraulics are similar ,components that are to small and overloaded with very small reservoirs do overheat the oil also .

Do enough oil changes and u notice the b4 and after difference . Running under 100 deg cel the oil DOES NOT come out old tired and smelly as running above this temp.

Car makers do the absolute minimum for all heat exchanger heat rejection capacity .

Once again oil companies donot recommend to regularly operate oil above 100 cel synthetics included . It shortens the service interval drastically.

patrol03 · Senior Member

AT oil in units that Cool fluid by passing it through the lower tank of the radiator would be reaching normal radiator temperature on return to the unit. Once a load is placed on the vehicle the temperature would normally rise and could could reach temperatures in excess of radiator BP depending on pressure cap rating and the increasing stress on the engine. As Swamp said change fluid often, but if an extra cooling condenser is fitted to the return line after the radiator, extra insurance is guaranteed for safer and efficient cooling of AT when towing.

In Iana's Nissan with the 7 speed Jatco, a heat exchanger is used to bring the AT fluid up to operational temperature quickly but the AT cooler operates independently of the radiator through a rather long condenser in front of the radiator. The engine working hard and radiator temperature rising does not add more heat to the to the ATF as it does in the normally used conventional system.

I change my fluid in the Y62 yearly and run 8 litres of Penrite through it. It is surprising how much smoother the box feels following the change. The expelled fluid is a little darker but no burnt smell of lacquering . Changing ATF is equally as important as changing engine oil if your AT is going to last the distance.

I drive my vehicle in manual mode when towing and use 6th as top gear ,never 7 thus reducing frictional heat on clutches and extra stress on torque converter. For the same reasons I do not use cruise control when towing.

iana · Guru

iana's Nissan, is in fact a Mazda BT50, it has a plate heat exchanger between the engine coolant and the transmission oil. most of our driving is in S mode, and we don't use cruise control.

patrol03 · Senior Member

Thanks for your information Iana. I didn't, in fact, know all of your details and I did get mixed up a bit after I read Radar's post. (senior moment).

iana · Guru

Dat's OK, I can't understand the logic that the designers have used for a vehicle supposedly designed for Australian conditions (joke), more likely its designed for the US of A, as their No1 choice of the rank in Ford utilities, would explain the lean towards the low temperature set-up.

Radar · Guru

patrol03 wrote:
Thanks for your information Iana. I didn't, in fact, know all of your details and I did get mixed up a bit after I read Radar's post. (senior moment).

I am learning as I go, thanking you for your thoughts.

iana · Guru

Just a note to add, while I was wanting to know operating temperatures, and I have a feeling that all that is quoted on the net relates to mineral oil, I am towing a large van with a standard ute, no modification's as yet. What I do notice, is that the vehicle speed has a lot to do with transmission temperature, keeping the speed down, keeps the auto transmission oil temp down, but just use a bit more foot and the temps really start to climb. So you want to race, expect problems.

Aus-Kiwi · Guru

Keep in mind if fluid is hot ? Imagine how hot bands & clutches are getting ?? Once overheated the damage is done, even if ATF is changed . Temp is basically the result of friction. Some mechanical sympathy is required although the ECU SHOULD but often doesnt protect drive train !! We are using way smaller engines these days . Pushing the durability threshold!! Then complain when things go bad !! Go back to 3 speed manual No synchro then you realise we actually have it pretty good ! Take that 5 % off throttle especially on hills . Possibly save, give durability ! Hmmm ? Me too !

-- Edited by Aus-Kiwi on Tuesday 21st of July 2020 09:07:36 AM

swamp · Senior Member

Hi
If u only keep your car under 100,000km then trade don`t bother with any of this !!
If u keep your car
Fit an oil cooler and change trans oil every 50,000km .Your done
Look up Rowell and Searle auto trans repairers 50 years exp and follow there recommendations .

www.unclutchables.com.au/2018/01/30/px-ranger-mazda-bt50-transmission-cooler/

Synthetic oil allows spikes of temp in sump oil but will not tolerate permanently being over 100 deg cel . You will never find a temperature recommendation that it will handle over 100cel !!!

-- Edited by swamp on Tuesday 21st of July 2020 10:00:18 AM

Trevor law · Senior Member

We have a 2010 200 series towing a 2780 caravan when we set off 7years ago we noticed that the engine and gearbox were getting rather hot so after talking to several people and taiking to Mr Google.i fitted a Scan Gauge and started to notice how the AT temperature would rise rapidly if it came to a hill ,or if in wrong gear .So started driving to the S G reading ,temp soon came down,also learned to drive in sports mode instead of auto .I have also fitted a lock up kit which also keeps the AT temp down significantly.Before the temp would be around 90-100 now 65-80,slightly better fuel economy as well so winner on both accounts.Very pleased hopefully I can save auto with lower temp and driving in correct gear .

Trevor and Jackie

iana · Guru

Yes we drive to the scan gauge, and I think some of the jockeys out there would get a rude shock if they installed one. The worst temperature rise I have had to control, was following a loaded water tanker up a steep climb at walking pace, however monitoring the gauge, and using gears kept it under control.

Aus-Kiwi · Guru

Oh no ask the dealer ? They say drive in D !! Well some do !!! Possibly talking to the cleaner ?

swamp · Senior Member

,Hi
Manufacturers use as little alloy, copper as possible for heating and cooling . It saves them 2cents per car . Australian vehicles receive no special attention. Many vehicles /machines have over the years have to be refitted b4 sale with larger heat exchangers . Many many European machines donot get refitted when new and get done at owners expense .

All of the above has payed my wages for 40 years !!

-- Edited by swamp on Thursday 23rd of July 2020 11:17:27 AM