4 speed noise

Any noise at all points to something not right.
If you can't find it externally, then it has to be internal, and if you don't know what it is, or can't figure it out, then it's probably time for a second set of ears, or a tear-down.
Slamming thicker oil into it is not the answer; that just comes with it's own issues.
Normally.... they are pretty much dead quiet, even with 100% ATF.
As to whining;
Normally.... the earliest noise comes from a bearing, and normally the noisy bearing can still drive thousands of miles. But as it wears out, the gears move away from each other under load, and the gears wear in a newpattern, making their own noise. Then when you finally change the bearings..... you are left with the noisy gears.
But if the noise originates in the cluster, or more likely the cluster pin, then the cluster is automatically moving away from the input gear, and the noise is the complaint of the highly loaded teeth.
My 367 tore all the teeth off the input and cluster teeth one fine summer day; ziiing! and I was walking.
But if the rear bearing,has play in it, then this will highly load the needle rollers in the back of the input, usually frying the nose off the mainshaft.

The point is; bearings are cheap compared to a rebuilt box.