I have a hum from my five speed '99 Maxima in mornings when the engine is cold. It fairly loud and only happens when I first start out in first gear. I am not sure what this is? I know that it has to do with the transmission and maybe the clutch. Is it the clutch slipping?

no try doing a fluid exchange with some quality gear oil. I hear the redline stuff is pretty good.

I have already done a gear oil change about 10,000 miles ago to Amsoil. The hum doesn't really affect drivability at all. It is just sort of loud and weird?

when you have a whine noise from the trans in the am then it gradually goes away as you describe it usually is generated from the bearings and is a result of the gear oil still being cold. what weight oil are you using?

It is the OEM weight of 80w 90 I think? I had it even before I changed my gear oil from OEM.

you may have a bearing that is worn. it will probably last some time this way before catostrophic failure occurs.

Or it could be a power stearing pump. If it hasn't blown yet, that is possibly what was 'humming'.

My trans hums a little and it has gotten louder since I have had the car. I don't think the last owner had changed the gear oil. I bought some redline MT-90, but once you change to synthetic gear oil you can't go back right? I think it may be to late though. Nick

Too late? Its never too late. Synthetic lube is soooo much better than dyno base products. Even the lousiest synthetic is far and away better than anything refined. It has to do with carbon chaining and the molecular "smoothness" of the compound. Even synthetic blend lube offers double the protection of conventional. It ist making noise, its already too late. It its a moving part, the synthetic may postpon failure, but it won't fix it.

Keep in mind though how the synthic stuff affects the syncro braking surfaces?? It has is definitie benifits with the gears and bearings but it also has that one serious draw back.

That is true, but I doubt a syncro is making noise first thing in the morning while traveling in gear. A syncro will "whine" if it is pressed too hard while changing gears and that is normal. A whine while while driving indicates a bearing that is imperfect and has either eroded surfaces or contamination. If iti s in all gears, its in the final, or maybe some of the hilical cut surfaces n the gears themself are at fauult. The only way to tell is to pull it and take it apart. The first post in this thread points directly at the first gear shaft bearing (99WhiteSe). The only way to fix that one is new parts, hopefully before a total transmision failure occurs (inevitable). The second phase of this post (574-240sx) probably has a gear that came out of a different set or has worn in abnormally. I am not familiar with what lube goes in the 240SX trans, but I am running ATF in a 1992 Ranger with 134K and no whines, no grinds etc. I had a 1990 Ranger that got noisy at 90K, and I switched it to 5W30 syn-blend motor oil (imporved syncro action, just like an overhaul) and all was well when the truck departed my ownership at 155K. Either way, the fix ain't cheap.

when I was speaking of the syncro it was regaurding the disadvantage of useing synthetic fluid in it. Yes I do realize it is not a syncro as the source of the noise.