Oil for main Gearbox, LT85

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Hamlet30

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Hi,
I am the happy owner of 110 from 1988, 3,5 V8 (naturally). I have been testing several lubricants for my main gearbox (MTF94, 15W-40 etc.). But they all seem a bit "dry". I mainly drive on hard surface, not terrain. Any suggestions to which oil is the perfect one?
 
castrol recommend 75w80 gear oil, ashcrofts who I bought my lt85 transmission rebuild kit from recommend 20w50 AND 6000 MILES OIL CHANGES.

I am leaning towards agreeing with them, I think that 75w80 is too thick and without regular oil changes the crap in the gearbox kills the bearings


any thoughts?

also to add to this split case gearbox no oil pump lt85 solid case oil pump
 
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Many thanks. This is an ongoing debate on the danish LR site. Many recommend the Red Line oil. Most go for fully synthetic oils, mainly due to the climate, high humidity and cold winter. Next time I change I will try 20W50. Any good advice on filling the oil on the gear box? Right now I use a long hose and a pump, but it is a bit tricky.
 
provided you use the side level plug you can fill from top plug:D
as stated before I would of used 75w90 but ashcrofts recommended 20w50, remember that the box originally specified 10w40 -20w50.
You also need to realise the box is not stressed and any oil will do,but if too thick will crunch.
it also has yellow metal components that do not like strong ep products.

my power steering uses ATF
 
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Definately dont use 85/90 in a LT85 way too thick .
20/50 maybe but synthetic is way to go and redline at that JMHO .
 
although this is a very late addition to this thread, it might be usefull to somebody:
- power steering oil: definitely NOT. a LR mechanic filled it with power steering, almost damaged everything in there. way to thin and it provide no lubrication after 2-3 hours of travelling
- 10-40 SAE, or 20-50 depending on the climate. Changes depending on the oil you use. I do not suggest the use of fully synthetic, although it lasts longer.
 
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Alekos "I do not suggest the use of fully synthetic, although it lasts longer."

Whats that based on ?
 
Always used 10/40 engine oil with no issues or 15/40 but have always used full mineral oil as it was never designed for fully syn oil I have seen on a quite a few on the fully syc the box tends to leak a lot more than on mineral oil
 
Cant be sure on split case lt85 but have run my solid lt85 on Redline Syn MTF since 1988 inc heavy towing in Australia JMHO but cant be bettered and no leak probs slight drip on transfer box but that lubed by Redline shockpruf . :cool:
 
tacr2man said:
Alekos "I do not suggest the use of fully synthetic, although it lasts longer."

Whats that based on ?
Click to expand...
Fully synthetic oil corresponds in different way to temperature than mineral oil or partly synthetic. they tend to go the the smaller viscosity range faster than the mineral oil, once heated up, thus giving less resistance to movement. In new engines & gearboxes this means less consumption. In my old LT85 this means more noise as the slack is not of a precision instrument...
I also have experienced problems with the engine, using fully synthetic: tappets knocking mainly.
it sure lasts longer cause it takes alot more stress to loossen up the intermolecullar bonds that keep its viscosity what it should be.
I did try the following solutions on my LT85:
1. mineral oil: best performance so far 20-50SAE (I'm in a warm climate)
2. hydraulic oil (suggestion of a mechanic sorry to say) DO NOT EVEN TRY IT.
3. fully synthetic: as astated above. I saw a big difference when the car travelled for an hour or so & more noise using the synthetic.
to answer your question: based on experiment and very few things I know as a Chemical Engineer.
 
Alekos , I do not wish to appear rude but I have to suggest that you study the performance characteristics of synthetic oil , as it would appear that they convey an explanation totally at odds with that expressed as your understanding .
These specifications logically correspond with why they are such an advance on older mineral oils , and would also seem to back up why they are much more expensive.
They may not be cost effective in certain older design mechanisms , but from my own experience in a very hot climate (not just warm) they can be fully justified. JMHO
 
I do not think you being rude, but I've done enough studying in my professional life on lubricants, organic chemistry and viscous fluid mechenics.
Not needing to go to advanced mathematics formulas, what you say about the performance stands. Synthetic lubricant molecules maintain the lubricating properties @ higher mechanical stress. they also correspond better to heat. Main characteristic is that they go at thin viscocity without loosing lubrication or "braking" as a mineral oil would. That is why they are a must for modern technology cars and most applications. So far I believe we are in agreement.
What I'm saying is that most of the old & cranky LT85's will sound better and behave better or if you prefer you'll feel them better at gearing up or down, cause they are NOT a high precision mechanism. They need an lubricant that will remain at higher viscocity, while stress & temperatures raisin'. Nevertheless you need to change the mineral more often as expected.
These days I'm trying a partially synthetic oil, just to find out if I can get the best out of both sides! Will let you know (if interested) after approx. 15,000-20,000Km. (3-4 changes)
 
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Hamlet30 said:
Hi,
I am the happy owner of 110 from 1988, 3,5 V8 (naturally). I have been testing several lubricants for my main gearbox (MTF94, 15W-40 etc.). But they all seem a bit "dry". I mainly drive on hard surface, not terrain. Any suggestions to which oil is the perfect one?
Click to expand...
Hello Hamlet30.. I have a 110 v8 with the split type lt85 Santana box. The car has 5000 kms on the clock and has been sitting since new in 1991. This would be a good reference as this landy is practically brand new. After sitting for 28 years oil changes was a must ( gearbox was working perfectly fine). Changed oil with 15/40 motor oil..grinds at second and rough at all other selections when cold. Changed to 20/50 motor oil(as reccomended by ashcroft)..same hard selections and grinds at second when cold. Changed to synthetic 75/90 gear oil and box works like magic..all selections and running are silk smooth. Split cases don't have an oil pump as the solid case lt85 do. This is the reason why oils for these two boxes is different I reckon. ( not mentioned in workshop manual)
 
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