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MG MGA - Fluid for the Ford Sierra 5 speed

What is the best fluid for the replacement Ford Sierra 5 speed trans?
Chris Velardi


The standard is 75W90 semi-synthetic.

Steve Gyles

Really ? Gear oil in the standard transmission .
Chris Velardi


That's what the book says, what internet searches say and what I have in my Type 9 box.

Steve Gyles

Yes, 75W90 synthetic. Moss sells Red Line. I have Lucas Oil in mine.
Andy Bounsall

Chris, I agree that it does seems wrong to use a heavy weight oil in the gearbox, but that's what the manual recommends. I use Castrol Syntec 75W90 in mine. Even with the mild CA climate the first few shifts are stiff but it warms up very quickly. Even then the first to second shift is probably the worst, but that could be a worn syncro.

60 A Coupe
Andy Preston

Andy P

Sounds like something wrong with your box. Even in the UK temperate climate I find the gear changing smooth and quick even from cold.

Steve Gyles

It is the MGA that uses unusual oil in the gearbox when it uses engine oil. Heavier grade gear oils are common in other gearboxes. Most Triumph cars use 80W/90 in the gearbox, with the TR7 using 75W/90.

M F Anderson

EP grade gear oil used a different viscosity scale from engine oil. There is not much difference in viscosity between 20W50 engine oil and EP75W90 gear oil. Ep oil is a no-no in gearboxes with brass synchro rings, as the sulfur additives like to eat the brass.
Barney Gaylord

The Ford type 9 has brass synchros.
James Johanski

Redline MTL 75W90 is not EP grade.

I had that stuff in my standard MGA gearbox for a 12,000 mile test a few years back. I didn't like the way it would shift from the first trip around the block, and was very happy the day I got back to using 20W50. I presume this has nothing to do with the Ford T9 unit.
Barney Gaylord

This thread was discussed between 13/11/2009 and 17/11/2009

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