I have a 2000 astro van with “flutter” noise that comes from the rear axle while driving after letting off the gas. the noise sounds like putting a baseball card it the spokes of a bike. the noise stays the same steering the van in either direction. it increases with speed (speeding up and coasting) the noise goes away with the slightest increase of gas but quickly returns when letting off gas pedal…someone suggested spider gears? researching spider gears on the internet suggest they are used for turning, could they cause a noise going straight?
Not being a tech with much pratical diff. repair experience (just bearings and seals) I would say no. What I would do would be to take the cover off the diff. and look for any gear with a broken or chipped tooth. Using a dye to get a idea of ring and pinion contact areas is not a task above the DIYer. Just compare the pattern to a picture in a book. This may lead you to either dismiss the diff. as the source of the noise or postively identify it.
I would like you to test off the gas and in neutral. How about giving those u-joints a real good inspection?
When it comes to Astro diffs. I have seen them destroy themselves when being used to tow over rated capacity.