tom1979

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Some friends of mine regularly take their Td5 Defender to Spain, where it can be 40*C or more at certain times of the year. They have noticed they get leaks on the transfer box in these conditions, so we're wondering if a different gear oil would be better, perhaps a 75w140 or something?

Does anyone have any thoughts on this ?
 
There is a cooler/fins that replaces the side plate. Think it also accepts a bit more oil.
As for oil choice no idea
 
Is the breather clear ?
Yes, that was the first thing I asked/checked, but it only does this in Spain.
There is a cooler/fins that replaces the side plate. Think it also accepts a bit more oil.
As for oil choice no idea
Those sump extensions are more for looks I think. All they do is increase the oil capacity slightly, so more oil gets hot. They also often foul the exhaust.
 
I do not see how changing the gear oil for some of higher viscosity will help [ it is a bit like when folks think that one shot grease in the swivel housing will stop leaks ] May slow it some to start but when hot all oils/grease thin out.
New seals, good flanges, double check the breather. The cooler plate extension do hold a fair bit more oil [half a ltr I think] and being made of alloy with fins to transfer heat away to the atmosphere.
Fitted correct way around should not foul exhaust.
 
ROW spec TD5 got a "oil cooler" from factory - EU didnt for some reason - I would add one if your in hot places regularly. but I would add the expansion pan as its a good/cheap upgrade

 
I do not see how changing the gear oil for some of higher viscosity will help
The viscosity would in theory be the same at "normal temperature" but a 75w140 would possibly maintain that viscosity longer?

Fitted correct way around should not foul exhaust.
We have had them not fit either way round. But in this case they would also have to lose their transfer box sump guard
 
It is up to them but I would not change box oil type. [ most of the time folks do this sort of stuff it does not work out]
The transfer box sump guard may well limit air movement in that area leading to overheating, horses for courses ect.
Only other thing could be a race car gear box cooler set up. There are specialist who can supply, search on line.
 
Yes, that was the first thing I asked/checked, but it only does this in Spain.
I guess the next step is to determine where it's leaking from

If you have the oppertunity, remove the tunnel and then give it an all over scrubbing with Gunk and the old washing up brush (don't use the new one - don't ask) plus a pressure wash.

This is the common one ... the seals on the intermediary shaft (FRC7439).
Not easy to spot/diagnose ...

 
There is a cooler/fins that replaces the side plate. Think it also accepts a bit more oil.
As for oil choice no idea

^^ This one

Those sump extensions are more for looks I think. All they do is increase the oil capacity slightly, so more oil gets hot. They also often foul the exhaust.

Completely disagree with this, the larger capacity will aid with cooling as there is more to heat up in the first place and the fins will aid in heat dissipation (all be it might be minor) vs a flat plate. I fitted one to mine and have happily driven 8k miles around Morocco twice with no issues. No fouling on the exhaust and no over zealous leaks.

ROW spec TD5 got a "oil cooler" from factory - EU didnt for some reason - I would add one if your in hot places regularly. but I would add the expansion pan as its a good/cheap upgrade

That is for the gearbox not the transfer case. the military ones had the same setup.

New seals, good flanges, double check the breather. The cooler plate extension do hold a fair bit more oil [half a ltr I think] and being made of alloy with fins to transfer heat away to the atmosphere.
Fitted correct way around should not foul exhaust.
This i think is the most pertinent reply, work out why it is leaking and replace the seals rather than trying to stop it leaking by adding thicker oil. What do they do with the vehicle to require a gearbox sump guard? the chassis does a fairly good job of protecting the boxs and unless you are doing some American style rock crawling all this is likely to be doing is reducing cooling and airflow around the gearbox's. Unlike diff and steering gearbox guards gearbox plates are not a common fit to every off roaded land rover so they must be a reason they have fitted one as everyone else who offroads their land rover happily manages without one, myself included.
 
That is for the gearbox not the transfer case. the military ones had the same setup.
I thought it worked as a heat sync eg. if the gearbox is cooler will pull heat out of the T case and if you then have the extra oil with an extended sump in the t-case this would then also help ? maybe wrong.

another thing to try Swepco 201 80w90 this can help reduce friction and heat.
 
Yes, that was the first thing I asked/checked, but it only does this in Spain.

Those sump extensions are more for looks I think. All they do is increase the oil capacity slightly, so more oil gets hot. They also often foul the exhaust.
They increases the surface area from which heat can escape from the box, both through the volume of the oil and the actual surface area of the sump. They do help, but I wouldn’t expect anything over a 10% improvement.
 
My 2c worth is that I lose 5 times as much trf box oil at highway cruising speeds - 100 kph - than I do dwawdling around in the bush at low speeds
The sump extender is reasonably well sold here in saffer land and the one post I have seen where the person had a temp sensor in the trf box was that at highway speeds things were a good 20 deg C lower after fitting it
 

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