24 replies to this topic

[adgjl7]

hi was wondering what oil is best to use in the m21. just had one rebuilt and would like to get it right thanks

[Dodgey]

This is my preferred oil.

 

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[lx308]

75/90 is what I've been advised to use also.

[adgjl7]

Thanks for your reply . ill go lookin tomorrow if I have time does repco sell it thanks again

[grumpy xu1]

No royal purple @ repco, autobarn is a stockist mate. Gary.

[hanra]

Box n diff

[grumpy xu1]

The liquimoly oil is 75w 90 for the transmission & 85w 90 for the differential both full synthetic & roughly the same price, royal purple USA made, liqui moly German made. Auto barn is the dealer for both. It's not cheap though i will promise you that. Don't be surprised to pay up to $200 for the oil for Trans & diff. But it would be what I'd use, gearbox can be easier to shift just with better oils, i will leave it at that. Gary.

[LJ RB30]

Box n diff

 

Reco'd the 3 speed in the Nanna Torana & put VMX in it cose i had some.

 

Was talking to an old mate a couple of days later about doin the box & using VMX.

 

His first comment was "GET THAT SHIT OUT OF IT!"

 

It will leak out of almost any gearbox! he said

 

Then i said that the box didnt leak before & its sealed up good so she"ll be right!

 

WRONG!!

 

It decided to leak out of the selector shafts & somewhere else that i cant remember now

 

Old mate said he has seen many a good box leak with that shit in it but when you replace it with ANY oil other than VMX & of the same viscosity it magically cleared up!!

 

I put Castrol 80-90 in it now & shed floor is dry!

 

My 2 cent anyway

[rexy]

I have used the Castrol VMX for a long time in all the Toyota boxes in the various cars - steel case celica, w series supra and r series supra. None have ever leaked. Very nice shift feel too.

[LJ RB30]

Think its what i ran in the supra box too with no issue.

 

Aussie 3 spd didnt like it

 

Old mate hangs around vintage regularity guys & has seen issues with VMX

[grumpy xu1]

If you were interested in the liquimoly the numbers & capacity are as follows engine oil part # 1212 5,litre bottle service refill is 3.4 litres.
M20 ect part # 4434 1,litre bottle service refill 1.9 litres.
Differential part # 1410 1,litre bottle service refill 1.4 litres.
Gary.

[IanC]

I bought some Royal Purple max gear oil for my gearbox. I meant to get 75/90. But I got 85/140 by mistake. Should I take it back and get the 75/90 ?. Cheers guys.

[RallyRed]

Thinkin' 140 is too heavy mate.

[dron]

Lighter the better, If you can keep it in there. Trick from years ago was to put Dex 2 in them to improve gear shift speed. The scrincos would never cope with 85/140. I would use a synthetic 75/90 or lighter rather than any older type oil, Lighter for the scrincos but still rated for a gearbox.

[RallyRed]

Hi again,
When I was pondering Aussie 4 speed oil I noticed this on tbe Penrite webpage for "1972 XU1" gearbox oil.
At the time I was about to use their synthetic gearbox oil. Anyway, I rang them/ web chatted to ask why " no substitution allowed!"?. The oil guru advised that these gearboxes have some bronze type bits in them, and THIS is the correct oil.
We did run the synthetic for a short time before this, but swapped back to the mineral 80w - 90.
Also of some interest, we have had race Aussies refreshed by 2 different experts and both say 80w - 90 MINERAL is the go for Aussie 4 speeds.
Others may have different opinions.

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Edited by RallyRed, 09 January 2025 - 04:53 PM.

[IanC]

Thanks Col. I use penrite in my motorcycle with full confidence. I have read that royal purple is pretty special. I ordered through supercheap. I have surched their Web pages, they seem to carry every royal purple oil except 75/90. Happy to go back penrite.

[warrenm]

It's too heavy for an M20, a 75w-90 GL4 mineral oil is better for the brass synchros.

[S pack]

I bought some Royal Purple max gear oil for my gearbox. I meant to get 75/90. But I got 85/140 by mistake. Should I take it back and get the 75/90 ?. Cheers guys.

Agree with our other wise members, 85/140 is too heavy for the aussie box.

[Indy Orange]

I used the 80W -90 Penrite gear oil for the Opel box ,no issues so far.

[bat 53]

i'm using 

nulon 75-85 full sinthetic

only driven 10 k's feels good 

[hanra]

I notice the Penrite Gear Oil 80-90 is listed for both the M21 and the LSD diff. 

[Indy Orange]

Yeah I used it for both Brad.

[axistr]

Stopped using 75 weight oils back in the late seventies. I have used 30w40 or even 15w40 engine oils in early gearboxes including M20-M21. Aussie 4 speeds don't like thick oil especially when cold. The syncrows get a real hiding when cold, I have found many transmissions have bundied off early due to thick oils. I use engine oil in large truck transmissions with 550hp and 2,200 lbs torque over 1.4 million km and still looks good when it was time rebuilt them. Still don't believe me ? most car manual transmission manufacturer since the mid 90s have recommended automatic transmission or 15w30 oils. The trend in oils over the past thirty years has been lowering viscosity, 5w30 oils are the norm these days.   

[claysummers]

Stopped using 75 weight oils back in the late seventies. I have used 30w40 or even 15w40 engine oils in early gearboxes including M20-M21. Aussie 4 speeds don't like thick oil especially when cold. The syncrows get a real hiding when cold, I have found many transmissions have bundied off early due to thick oils. I use engine oil in large truck transmissions with 550hp and 2,200 lbs torque over 1.4 million km and still looks good when it was time rebuilt them. Still don't believe me ? most car manual transmission manufacturer since the mid 90s have recommended automatic transmission or 15w30 oils. The trend in oils over the past thirty years has been lowering viscosity, 5w30 oils are the norm these days.

Same deal with the Borg Warner five speeds in VH VK when they came out. Everyone was having issues shifting back to second, solved by using ATF or a particular Castrol oil that was much thinner than conventional.


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