Chevrolet Repair: 1995 chevy g20 transmission noise

Question
i recently purchased a 1995 chevy g20 conversion van with a 5.7l motor and automatic transmission.it has 160,000 miles but runs and drives excellent and appears to be well cared for. it started making a whining noise only when moving. i had a friend who is knowledgable on cars look and he said it seems like the noise is coming from the end of the transmission where the speedometer is attached (i forget the exact words he used ) but we had it up on jackstands and he climbed under to get a better perspective.the previous owner did tell me they had repaired the speedometer cable recently. my question is could this cause major damage to the transmission if not imediately fixed and is it a fairly easy fix? thank you

Answer
Whining like you are describing ,most commonly comes from the differential. Check the gear oil in it . I am pretty sure the nylon speed-o gear wouldn't cause a whine. Does it do it in high gear? The planetary system of gears in the transmission are used in first and second gear. Third and o/d they are not, but bearings are commonly employed for all operations.I doubt the speed-o is the cause of the noise. With the mileage that is on the vehicle there is some wear that comes along with it.It is common for some barely audible whining to radiate out from the gears of the rear end and transmission to a lesser extent. As long as it does not seem to be getting worse and isn't so noisy that it gets the attention of fellow drivers, you're probably not having any problem. It depends , how noisy is it?