legacycentral bbs

on certain transmissions it is common practice to overfill the oil slightly. does anyone do this on their 5mt and by how much? how many quarts exactly? I cant think of any real negative effects of this, but I could be wrong. comments?

I would imagine that if you overfill the transmission enough you could get oil frothing, which would reduce the oil's ability to form a film between parts, resulting in potentially damaging metal-to-metal contact.

Why not just fill it to the correct level?

I heard somewhere that it can keep the gears lubed a little better. it may not be applicable on a 5mt, but some trannies have oiling problems. something about helping 3rd gear.

seems like this would put extra stress on seals and stuff

0perose wrote:seems like this would put extra stress on seals and stuff

That's what I would think, and it's no picnic replacing seals on Subaru MT's...

206er - Hmm, so you're wondering about the possibility that FHI engineers decided to make the specified capacity lower than would be ideal for lubrication. The only reason I could imagine for anyone doing that would be that maybe less oil would mean less drag as the gears spin through the oil.

I doubt that's the case, though. For one, it seems like the reduced lubrication would cause more friction anyway. And for another, I would just have a hard time believing that FHI would have done something like that to us.

^^^ Agreed. Any engineer that would decide to have added friction over a slight loss of power in the driveline for a market car is an idiot. Perhaps somewhere out there are old transmissions that do better between two particular gears when they have more than specified oil but it's certainly not ours .

turns out the guy I heard it from was referring to a SM-465 which Im sure is not designed as well as a 5mt. I'll just be filling up to the correct amount with good ol dino oil then if I decide I need to I'll switch to something like redline or royal purple.