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M46: redline MTL or racing type F

cathoderayfish

cathoderayfish

New member
Joined
Jan 8, 2025
My m46 grinds 2nd to 3rd when shifting quickly (no grinding if I hold the clutch for a while) and the shifts can be overall a bit stiff. I have heard some discussions online about putting redline MTL in is really good, whilst others say that redline racing type F is better for the m46.

Has anybody had any experience with either fluid being better or worse?

My m46 currently has standard type F in it and has a working overdrive (which I would like to keep working:) and about 200k miles on it, clutch seems OK (not great, but OK), unsure if it's the original. I am aware that fluids like this are bandaid fixes and I would need to rebuild trans for full fix, don't have the time or money for rebuild rn though.
 
I’ve had issues with MTL not working great when cold.
Redline racing type F works really well in m45/m46/47 transmissions in my experience.

Since you have a working overdrive and cone clutch, I’d go for the racing type F.
 
I'm a dope and I've used MTL in my M4, M40, M41 and M46 gearboxes.

I think it was fine in those mentioned, but have no empirical evidence to prove it from a mechanical standpoint.
All I know it that my M4, M40, M41 and M46 gearboxes haven't failed in over 100,000 miles.

Like I said, I'm a dope and am happy to provide this worthless information. :lol:
 
culberro said:
I’ve had issues with MTL not working great when cold.
Redline racing type F works really well in m45/m46/47 transmissions in my experience.

Since you have a working overdrive and cone clutch, I’d go for the racing type F.
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how cold and how much of a problem was it? This 240 gets exposed to temps around 100f as well as temperatures of like -40
 
cathoderayfish said:
how cold and how much of a problem was it? This 240 gets exposed to temps around 100f as well as temperatures of like -40
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Dang, that cold temp is brutal. I can say that with type F in -20C it did fine in an m46.

The mtl wasn’t happy when it was anywhere near freezing.
 
culberro said:
Dang, that cold temp is brutal. I can say that with type F in -20C it did fine in an m46.

The mtl wasn’t happy when it was anywhere near freezing.
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OK, in that case, I think I'll probably go for the racing type F then, how much of an improvement in shifts is it over normal type f?

So far, I've only been in the aforementioned extreme cold with this car once, but it seems that my life may be taking a turn in which I'll be spending quite a bit of time in the far north, gonna have to prepare her other ways for such a life (undercoating, better battery, fix the airbox thermostat, maybe even block heaters [seems like an unfun process]) Because she was not happy last time, among the woes of starting, shifting with the conventional type F didn't feel great at all:)
 
cathoderayfish said:
OK, in that case, I think I'll probably go for the racing type F then, how much of an improvement in shifts is it over normal type f?

So far, I've only been in the aforementioned extreme cold with this car once, but it seems that my life may be taking a turn in which I'll be spending quite a bit of time in the far north, gonna have to prepare her other ways for such a life (undercoating, better battery, fix the airbox thermostat, maybe even block heaters [seems like an unfun process]) Because she was not happy last time, among the woes of starting, shifting with the conventional type F didn't feel great at all:)
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If you’re spending a lot of time in really cold weather, something even lower viscocity might be needed.

In all honesty, the last time I had regular type F in a Volvo was over 10 years ago. It worked well enough, and that m46 was BEAT but never died.
 
I have not looked into racing ATF, but racing motor oil has no detergents (very short change/tear-down intervals), and therefore is bad juju on the street.
 
mikep said:
I have not looked into racing ATF, but racing motor oil has no detergents (very short change/tear-down intervals), and therefore is bad juju on the street.
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From what I can find on this particular redline ATF, it’s a higher viscocity full synthetic type-f. it cleans things just as well as regular atf, but I haven’t looked into it regarding detergent additives.
 
I recently swapped whatever dark red fluid was in my M47 (ATF?) For redline MT90 (meant to buy MTL, oops) seeing that it's really cold outside currently it shifts a little worse when the car is ice cold, but once you get a few shifts in it shifts as good or better than whatever was in previously. MTL would probably solve the issue entirely, on an M47 with 300,000 miles on it. My theory is that Volvo specified ATF on the M46 because ATF isn't "slippery" and allows the cone clutches in the OD unit (which is basically one gear out of an auto trans) to grab where gear oil wouldn't, even though ATF itself doesn't make a very good gear lubricant. Redline advertises MTL as "not slippery" to allow synchronizers to grab better which could be helpful for the OD, basically comes down to which part do you want to rebuild first. The OD, which likes ATF most, or the Gearbox, which likes gear oil most.
 
Type F has less friction modifiers compared to the rest.
When i need low viscosity posi fluid i mix 50/50 dexron and synthetic 90.
 
I've used Redline Type F in my M46 for a couple of years. Definitely more viscous than regular type F.
Can feel a bit stiff on on frigid Mornings (0F-20F) but seems to work well once gears move around a bit and feels great at operating temperature (About 165F if I recall, for the M46) I like it better than Amsoil Type F and regular type F.
 
Well, after reading all this, I'm still quite conflicted:LOL: Sounds like either one is an upgrade from normal type F. At this point, main concern is cold weather. IDK how much the trans is actually able to heat up when outside temp is well below 0f, I don't mind shifts being physically hard and unsatisfying, as long as the fluid still does a good job of wear-protection and all that at such low temps.
2nd to third does grind a bit at higher rpms unless one holds the clutch for a second or two, so I'm inclined to go for whatever one is better for the gearbox itself in hopes of maybe aleviating that issue a bit. Any more anecdotes about MTL and others in extreme cold would be appreciated:) Thanks to everyone who has replied thus far!
 
Pause a split second between shifts, this gives the gears a chance to stabilize. The gear lube can also be the issue, hypoid,atf syn oil, I run Red Line MTF in my MG MIDGET, works great. It's the only car that I have right now that has a standard.
 
283SD said:
Pause a split second between shifts, this gives the gears a chance to stabilize. The gear lube can also be the issue, hypoid,atf syn oil, I run Red Line MTF in my MG MIDGET, works great. It's the only car that I have right now that has a standard.
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I have been pausing between 2-3 for a second or two (depending on rpm), and that eliminates the grinding but I'd rather not have to:) double-clutching also works, but even that can grind if I am shifting up around 5k or higher.
 
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