My '88 Chevy Suburban has the 700R4 transmission in it. After roasting it this past summer, I had it professionally rebuilt by a local guy. He made some modifications to it and installed a shift kit. I am now noticing a slight whining noise when it is in gear - not loud but audible - it goes away in park and neutral. Fluid is in operating zone and it shifts fine. I know hydraulic pumps make some noise under load - is this normal for this transmission? This is my first 700R4.
Any ideas?

It could be the pump, and it could be a bad planet it is hard to say, Is it more noticeable in reverse?

No, I can hear it in both forward and reverse.

I'm experiencing the same things on a 4L60e. I'm swapping out converters this weekend, will let you know the results.

there is something wrong. it should not make any noise. mine didnt.