Thread: Auto Transmission Cooler

landrover transmission cooling is adequate for all climate conditions PROVIDING you drive it sensibly and do all the right things to help the gearbox. (which you should be doing anyway to prolong the life of the boxes clutches, tc and the contents of the fuel tank)

IF however you are going to push it beyond the anticipated normal use of the vehicle (which means towing over 2T regularly, not kicking it out of drive and locking it down when towing, staying in high range in the sand and working the auto to get through soft stuff and taking the engine over the nominal rated power levels) then the Trans cooling is marginal at best for most Australian conditions. You have 2 choices here 1. More regular oil changes on the auto (and I mean changing the pan oil with every engine oil change) or 2. fit better cooling.

The best thing you can do for your auto is kick it into neutral when you dont need it to be driving, if its hunting between 2 gears lock it down on the shifter, Use Low range whenever you need creeping speeds (dont just ride the brakes back) and service it regularly

My current reccomendations for servicing of the autos is

For regular usage pan oil change with every second engine oil change and a filter on the 4th

For harsher use a pan oil change with every engine oil change AND a filter on every second.

Full flush out with every second filter in the auto.

Heres how I do the pan oil change.

Vehicle drives in with the engine hot and the auto at working temp. Engine shut down, drain plug out when the oil is no longer running (less than 10 drips a second) plug back in add 2l of oil, start engine then top up to correct oil level. 20 K test drive then recheck oil level.

for just a pan change plan on 6L of oil
for a filter change plan on 10-12l of oil
for a full flush plan on upto 20l of oil depending on how dirty/contaminated the trans cooler, trans casing and TC were. (my record is 60L of flushing oil before it came clean)

After fitting the P38 cooler I then got the dremmel out and attacked the front grille to improve airflow. I haven't done any big trips yet or towed anything but the temp gauge I have on the cooler pipe (outlet) shows that I am running another 5 to 10 degrees cooler since the grille was modified. I noticed a temp drop of between 20 to 30c after fitting the P38 cooler and have not yet managed to exceed 100c since fitting it whereas it would often exceed 120c before the new cooler was fitted.

In my experience what really gets the Gbox temps up is sand driving and towing up steep inclines without reaching lockup speeds which is obviously when the most friction is occurring in the transmission. Its amazing how quickly the temps drop up to 30 -40 degrees on the digital guage once you hit 80kmh and lockup occurs, most likely due to the pressure increase in the cooler pipes during lockup and therefore more fluid pushing through the cooler as well as less friction in the clutches. Another observation is after stopping to let the box cool down after a steep incline the temp continues to rise for a few minutes and this could be due to less fluid going through the cooler, I've tried toggling through neutral, drive and reverse but the temp still rises so in my view its best to keep going and try to hit lockup speed if you can (even if it means low range for a while).

Pic of modified grille attached, I should have sprayed the cooler black before I put the grille back as its quite visible, might do that later but reliably is more important than looks with this car : )

Hi I have looked at the P38 trans coolers, which one do you use? the one for the auto in the diesel looks a lot bigger than the ones in the v8.
Mine is a 95 v8 auto with air cond so which one should I use?
Thanks Peter

Originally Posted by Discomark

Its amazing how quickly the temps drop up to 30 -40 degrees on the digital guage once you hit 80kmh and lockup occurs, most likely due to the pressure increase in the cooler pipes during lockup and therefore more fluid pushing through the cooler as well as less friction in the clutches. Another observation is after stopping to let the box cool down after a steep incline the temp continues to rise for a few minutes and this could be due to less fluid going through the cooler, I've tried toggling through neutral, drive and reverse but the temp still rises so in my view its best to keep going and try to hit lockup speed if you can (even if it means low range for a while).

whats happening is that you are taking the heat load off of the cooling system because when you hit lock up you are no longer driving hydraulically you are driving mechanically. The temps come down quickly because you have full air flow through the cooler and are still pumping oil due to higher engine revs. The quickest way to cool the auto is to put it into neutral and then hit high idle (bout 1200rpms) The reason you get the temp spike when you stop is because the oil then picks up the latent heat from all the metally bits and continues to swap the oil out of the TC and the sump. Its the same concept as when (on an old school iron engine) after extensive high speed running if you come to a near instant stop and let it idle the heat from the heads and bores is enough to boil the coolant because the radiator is no longer getting the airflow to remove the heat.

My D1 autobox is about 35000km old now. During recent simpson trip I saw transmission temps of up to 100 C. These occurred on formed roads where I could not safely maintain lock up speed in 3rd, generally on corrugated/sandy tracks. Is 100C of any concern?
During the actual desert crossing I drove conservatively and did not see temps over about 70C.

I am confident that extended low range sand driving or climbing in hot weather would see my temps exceed 100C so am considering the P38 cooler mod to protect my new tranny.

Dave, others - given that I dont generally tow and drive fairly conservatively, have full synthetic fluid - what kind of interval ( km and/or time) would be sufficient to get a good life out of this box?

thanks
Lindsay

How long do these transmission oil coolers last before needing replacement? Mine is the original on the 300Tdi, the gearbox has just been rebuilt at 340,000 km and I was looking at the oil cooler and wondering if it should be replaced. It looks OK from the outside, but how do you tell if its OK inside?
The vehicle runs very cool - radiator replaced a while back - but I don't have a gauge on the transmission to know if there is a problem there.
It tows a camper trailer and has been up Cape York and similar places without a problem, but I expect sand, not the Cape, would be where the vehicle would run the hottest.

Originally Posted by Linds

During recent simpson trip I saw transmission temps of up to 100 C.
Lindsay

Where are you measuring the 100c?
I still reach 100c at the cooler line (outlet) even with the larger P38 cooler fitted. This is when towing up long hills on a hot day mind you.
I set my alarm to go off at 110c and I'm not concerned to hit 100c for short durations especially with full synthetic fluid.
Before I fitted the bigger cooler the factory auto temp sensor would go off when towing and that is supposed to be set at 135c

Cheers
Mark