1982 4x4 with 5 speed. Was driving on the freeway and noticed a high pitched noise coming from the drivetrain when I pushed the clutch in to down shift. Got towed home to not wear out any components. Noise starts at 15-20mph when I:

- push the clutch in
- let the clutch out in neutral
- let the clutch out in gear

and continues if I am decelerating. I thought it was the transmission and have had a look inside but I’m not convinced that’s the cause (as all the gears look good). It might be the input bearing (and there is a bit of play in the input shaft of the L52 (maybe 1/8-1/4" of play)). I also noticed that the truck felt a bit shakey when I reversed it up into my driveway. Any help or insight would be awesome!

As of now I have the transmission, transfer case and driveshafts dropped.

Bought the MarlinCrawler clutch, because I might as well put a new one since the transmission is out.

 

I had a U joint go similar--sound only when the drive shaft wasn't applying torque. But it was a grinding noise as one of the caps was in 2 pieces. High pitch is usually a bearing. Did you to check the oil in the differential? Any metal shavings in the bottom of the transmission? How do your U joints feel/look?

 

Throwout bearing.....