HOT GEARBOX TUNNEL - RIGHT OPERATING OIL TEMPERATURE OF LT95

alessandroV8 · Post by **alessandroV8** » Fri Oct 24, 2008 2:13 pm

Dear land rover V8 friends,

My gearbox is now rebuilded in the Uk and work quite and smooth, but the gearbox tunnel shows still a high temperature (38°C) on the superface of the gearbox tunnel with 14°C outside. Inside in the cabin my mechanic has misured a temperature of 28 °C. In summer I will make a sauna.
Fo clearing this mistery, I have to make any investigatons.
The first, is to know if my gearbox works now with a correct oil temperature.

Maybe someone knows where I can get the operating oil temperatures of the LT 95 4 speed gearbox and at which rpm and which speed and external temperature.

I know it is a very difficult technical query.

Thank yuo for helping
Alessandro

stirlsilver · Post by **stirlsilver** » Fri Oct 24, 2008 10:24 pm

I'm pretty sure that 38deg is nothing for the gearbox. I remember reading about someone who was driving hard for a long time and the gearbox reached a temperature over 100deg.

I don't think there will be much that you can do about the temperature of the box, especially since some of the heat is contucted from the engine. Put some insulation over your gearbox tunnel and it should help reduce the amount of heat that gets inside the cabin.

disco2hse · Post by **disco2hse** » Fri Oct 24, 2008 11:30 pm

The gearbox uses engine grade oil and the engine's normal running temperature is 86 C or more, so 36 C for the gearbox is minimal.

Series III's are typically hot runners, which is why you have vents in the front. As Stirling said, if the heat bothers you, just put some insulation matting under the tunnel to shield it.

Some people do put oil coolers into their gearboxes but from what I have seen, that is for places where the ambient temperature is in excess of 40 C.

Edited to add: You should find most of the heat in the gearbox has been transferred from the engines itself, but also a lot of the heat in the cabin is coming in through the firewall and from the exhaust pipes. So if you intend to add heat shielding you will probably also need to put some in around the firewall.

djam1 · Post by **djam1** » Sat Oct 25, 2008 9:33 am

I live where the temperatures are around 50 degrees C and have never had an issue with an LT95 and heat.
Make sure you have the right grade oil in it if it sounds ok you have nothing to worry about. I have personally towed close to 2 ton with a Range Rover Classic in 54 degree heat without issue.
I have also run Series Land Rovers in conditions that had our thongs melt and stick to the floor so your 38 degrees really isnt that bad.
If you are really concerned about run synthetic engine oil of around 15 w 50

stirlsilver · Post by **stirlsilver** » Sat Oct 25, 2008 11:45 am

I use Castrol EPX 80W-90 in my gearbox no problem.

As I understood it the reason landrover specified engine oil back then was because there wasn't any good quality gearbox/diff oils around then. It is completely different today so it is suggested to use gearbox oils now.

But it seems that either option works just fine

firemanshort · Post by **firemanshort** » Sun Oct 26, 2008 9:47 pm

90W is too thick for cold temparetures. I have that in mine and I can not shift the truck without effort and grinding unitl I get it warmed up.

alessandroV8 · Post by **alessandroV8** » Mon Oct 27, 2008 8:33 am

The problem of the car is that the tempertaure of 38 °C is not the tempeature of the gearbox inside or the temperature of the gearbox, but it is the temperature of the surface of the Gearbox aluminium tunnelcover in the cabin.
And this temperature aluminium cover heats the cabin up 28° C - now with only 14 °C outsides -
What can happen in summer with 30 °C outsides?

Maybe it is possible that the aluminium cover had an insulation underneath fitted and now after the restoration I lost this insulation. (I don't have an insulation under the tunnnelcover)

Is in your stage 1 an insulation under the aluminium tunnel cover present?

Thank You for all your replyes.

Alessandro (south tyrol - Italy )

Andy Dawe · Post by **Andy Dawe** » Mon Oct 27, 2008 10:31 am

EP90 and EPX 80W-90 are completely different. The EP 90 is the thick nasty smelling oil used in diffs and transfer boxes and series main boxes pre 2000ish.

You are right it's not suitable for Stage one main boxes as it's too thick for the oil pump to deal with.

EPX 80W-90 is a new high shear low viscosity gear oil which feels and runs more like engine oil. It's now used in axles and transfer boxes of post 2000 discovery etc. Unlike engine oil used in gearboxes it survives the bashing shearing and abuse the gears give it. It stays cleaner and holds it's original structure longer.

The only drawback is it's not cheap.

The disco 2 uses EPX 80W-90 as standard and the car has one of the quietest transmissions for a 4x4.

stirlsilver · Post by **stirlsilver** » Mon Oct 27, 2008 12:18 pm

Thanks for shedding some more light on that Andy.

The minute I put this oil in the box the gearing became easier. Even when cold.

Larosto · Post by **Larosto** » Fri Jan 16, 2009 6:48 am

Hi,

here again a question about gearboxoil in the LT95: The 80W90 is rather thick, and when it is cold it is only a little bit thinner than the 90 oil. Someone told me, that when it is very cold, it may happen that the oilpunpgear of the LT 95 would be destroyed, `cause it`s made of plastic.
On the other hand, when it is cold, the engine oil 20W50 is rather thick too.
(Temperature is sometimes below0°C)
Does anybody know something about this? I don`t want to crack my gearbox.

regards
Horst

Larry · Post by **Larry** » Fri Jan 16, 2009 8:41 am

Alessandro,

Mine never had any insulation, but I had considered fitting some, or even cover the underside with reflective foil.

I always considered the heat from the gearbox tunnel as secondary heating, and in the winter was very grateful for it. But in summer, it could make the interior quite unpleasant.

The vents on the front and the ones in the safari roof are fantastic when doing anything above 20mph, but getting stuck in traffic could be a nightmare with the gearbox tunnel and bulkhead still radiating masses of heat with no cool air coming in.

I wouldn't worry though, the gearboxes do run very hot and as has been said, alot of heat gets funnelled down the tunnel from the engine bay.

sebking · Post by **sebking** » Fri Jan 16, 2009 10:01 am

As part of my soundproofing this weekend I'll be putting dynamat on the seatbox and on the gearbox cover.

Will let you know the difference. It is both heat and sound proofing.

map1275 · Post by **map1275** » Fri Jan 16, 2009 10:55 pm

I don't have a laser temp gauge to measure all this. They're damn expensive. But as ambient temp is going to be anywhere up to 40 deg C, what's the problem?
Seems to be as lot of over thinking.

The engine's thermostat won't be opening till at least 82 deg. Operating temp will be above this. Conduction will send a lot of this heat down the bell housing, plus the heat the box is generating.
As the standard tunnel only has the vinyl cover, radiation may well keep this close to gearbox temp. Measuring the base of the gear stick may be more accurate as this will be relying on actual conduction from the box.

Otherwise, go for a drive in someone else's Rover and take the laser gauge with you. In fact, go for a drive in absolutely any car that's to hand.

stirlsilver · Post by **stirlsilver** » Sun Jan 17, 2010 10:36 am

From something I have just discovered.

DO NOT USE EP or EPX oils in the gearbox or transfer case, this oil contains suphur and phosphorus and can corrode yellow metals (which the LT95 has) under high temperatures. If you are going to use a gearbox oil make sure it specifically says it doesn't contain these compounds!

map1275 · Post by **map1275** » Sun Jan 17, 2010 11:18 am

I doubt you're ever going to find any oil container anywhere that states what it doesn't contain!

EP.... Extreme Pressure, sulphur is the lubricant additive in high shear applications.

As per your handbook, 80/90 EP is only in the diffs, hubs and axles.

Stage 1 V8