raceboy

I have a theory as to why the tranny grinds. I don't think it actually has anything to do with the tranny at all. I beleive that the culprit is the fact that the car does not drop revs quick enough. I think it is caused by a lag from the electronic throttle combined with an extremely heavy flyweel. I think this keeps the revs higher than is needed for the synchos to engage properly. Eventually, this starts to wear the synchros and you start to get the grind. Oh well, that's my theory, what do you think?

sakred

iTrader: (4)

when i went in for my tranny replacement.i asked the nissan engineer why allot of people were experiencing the grinding. he said it was a design flaw. nissan did not make the syncros out of brass like conventional auto makers. they decided to use steal. im not sure as to what extent this is true. im not that big of a gear head. anyways raceboy how many times have you gotten your tranny replaced?

raymanZ

My understanding is that 1st and 2nd have dual synchros made out of brass, 3-6 are single ones made out of steel.

So far, for most people like myself, the tranny had to be replaced for 3rd gear grind. Not sure why it is only that gear, although I have some ideas in line with what was mentioned already.

RaymanZ

elektrik_juggernaut

if it were too heavy of a flywheel, wouldn't it cause the tranny to grind third gear all of the time? My symptoms seem to disappear once the tranny has totally warmed up. I like your theory though, cause it would mean i could fix this with a lightened flywheel, a route i was planning to take eventually anyway.


From what i've seen of my own grinds, i believe it has something to do with improper lubrication on start-up....perhaps cold lubrication could be achieved with brass synchros, but i do remember seeing a couple of posts about 2nd gear grinds also........i'm assuming that this is the first time this tranny has ever been used by Nissan.....if thats the case, then perhaps there are too few channels for oil to flow through.......i know for myself, i've been able to stop the grinds by running the car through all the gears before i start driving, and shifting into 3rd at low R's while the tranny is still warming....once it's warm, it's fine

KY350

I've had my car for 1 month now and not had any problem with my tranny. However, when the engine is cold, I change gears in 1st and 2nd between 3-3.5k revs and 3rd, 4th and 5th between 2-2.5k revs. Perhaps I am not revving it high enough so the tranny doesn't have to drop so many revs as in raceboy's theory??? At what revs do you change gears?
Improper lubrication seems a very plausible cause for this problem, especially if the grind does not occur once you row all the gears before take off.

travelmadness

i always blamed my grinds on something i must have done wrong -- like engaging the clutch late, or pulling the shifter too quick... the more i read about others with grinding problems i'm starting to think that it isn't my fault. i'll have to pay a little more attention the next time it does grind. it has happened maybe 5-10 times in the past few months, which is weird, because i always drive manual transmission cars, and i don't usually have problems with grinding.