Diagnosing gear whine

>>16810417

What's weird is I have the same problem - a whine from the gearbox most prominently in second gear. What's weirder is mine is in my Fiero. I have no idea what the problem is, although I've heard it's not a big deal at least in my case. Still, I would like to know.

>>16810417
Countershaft bearing. Bearings make noise over multiple gears more often than not.

Alternatively, it's the Input Shaft gear that drives the Countershaft that has developed an issue due to wear. That would necessitate replacement of the Input and Countershaft since those gears would have worn togther. Either way you're looking at a teardown and inspection.

This assumes of course that they don't whine naturally. I mean, we've got two out of two examples here making noise so as far as we here itt know that's normal

>>16810487
Already did all the bearings, they're all solid.

>>16810417
>possibility of bearings eliminated
It's the bearings.

>>16810417
Change your oil, even if you changed it recently, and see if there is metal shavings in there, buy a magnetic drain plug if you don't have one already.

Did they make noise before changing bearings and synchro? Can you absolutely exclude the possibility the the replacement job hasn't been done perfectly, thus causing the noise?

Did you do the job? If yes, did you inspect all the gears for chipped teeth? A gear doesn't need a whole tooth missing to make noise, even a little bend or deep scratch can make a ton of noise when the gear spins several thousand times a minute.

Did you put the correct oil in there? For example, gearboxes rated for an API GL-4 can't be used with a GL-5 because the latter corrodes the brass in the synchros. It's unlikely that this corrosion could be so severe if you only replaced the oil a few months ago, but it's still a thing to consider.

Does the whining stops if you are at speed and you press the clutch pedal? Because if it does, then the noise might be coming from the engine rather than the gearbox, because the gears are still spinning as long as you are moving.
Also when pressing the clutch at speed, try to brake hard to exclude a gearbox noise happening only when there is considerable load applied to the gears.

>>16811018
Running redline MT-90, cleaned out shavings last time which wasn't too long ago. They made noise before changing all the bearings, all bearings are solid now. I didn't take too close a look at the gears. Correct oil is in. Whining stops with clutch in UNLESS I'm in second. Will try braking test soon.

>>16812557
If "last time" was when you changed the bearings, then you should check again to exclude the possibility that something broke or was misplaced when reassembling the gearbox, check again and reuse the oil if it's clean

>>16813225
Last time was about 3 weeks after doing the bearings. Everything felt solid, I re-replaced my input shaft bearing to see if that was the cause but it wasn't. Nothing blew up. Just did some testing today. I'm starting to get really certain it's second gear.

Say I get up to speed, around 40 in 4th, clutch in, disengage 4th gear, put pressure on second, I can hear kind of like a "PEW" that lasts as long as I'm putting pressure on the synchro. Doesn't happen with any other gear.

Generally whining in a gearbox is chipped or damaged gear teeth, bearings will cause a growling noise generally, and synchro problems only really show up during shifts, unless the synchro is so bad that it jumps out of gear

Also, I'm not really familiar with that transmission, but most reverse gears are straight cut, so whining in reverse is usually normal