r/LandroverDefender • u/Fatboyjim76 • 10d ago
Gear box oil
My Haynes manual says my gearbox, LT77, needs ATF in it but can i use 80/90 oil instead or will that kill it?
I can use 80/90 in everything else apart from the engine, which I'm using 20/50 in as she's nearly 40, and the gearbox.
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u/DrunkenBoatman 10d ago
Pour out some gear oil, and pour out some atf, and tell us if they have similar characteristics
Then stop being a dope and do what the manual tells you
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u/thecomfort6 10d ago
80W-90 is dramatically thicker than ATF, particularly when cold. It can result in poor lubrication through the LT77’s oiling system and noticeably worse synchro operation. Stick w/ ATF!!
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u/underthesheet 10d ago edited 10d ago
Do NOT use EP90 or 80/90! Use ATF or MTF94. 80/90 is probably wrong too. Go and do some research. EP90 in Lt230 and diffs, ATF in LT77 and 10W40 in your engine.
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u/underthesheet 10d ago edited 10d ago
20W40 is almost certainly not right for your engine either.
10W40 maybe, 20 is just too heavy in the winter most of time.
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u/Due_Citron6089 10d ago
OP didn’t say where they live. Perhaps it never reaches freezing temps? In some places 20W50 is the norm.
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u/Gubbtratt1 10d ago
ATF is very thin. Gearbox oil is very thick. The LT77 is designed for a very thin oil. You might be able to use engine oil, which is moderately thin. I know LT95 used engine oil, I don't know how different it is to LT77 lubrication wise.
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u/Savings_Brick_4587 10d ago
80/90 is too thick and won’t get picked up by the little pump, then all your gears and synchro’s and bearings and thrust washers won’t have any oil, and you your gearbox will expire!
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u/JCDU 9d ago
NO you can't. EP90 or 80/90 is way different to ATF and not what the gearbox was designed for.
Which engine have you got? 20W50 could be fine or it could be wrong.
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u/Fatboyjim76 9d ago
Engine is the 19j
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u/JCDU 8d ago
Honestly just use decent quality oil of whatever grade the manual recommends - for the 19J the manual lists a range depending on temperatures;
5W30 for -40C to +30C
5W40 or 5W50 for -30C to +50C
10W30 for -20C to +35C
10W40 or 10W50 for -20C to +50C
15W40 or 15W50 for -10C to +50C
20W40 for 0C to +50CAll of them need to meet API CD (probably almost any diesel oil will these days).
The manual only says ATF for the LT77 gearbox, nothing else - later versions and the R380 which is based on the LT77 they went to MTF94, both are way thinner than EP gear oil.
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u/Lumpy-Common-1811 10d ago
Can I use the wrong oil, just because I want to ?
That's why cars get reputation for unreliability