I recently purchased a 1988 3500 Silverado Dually 454, TH400. I've looked and read about this "ticking" sound coming from the transmission. I thought it was the engine, but the ticking does not get louder under a load or when I hit the pedal. Prior to shifting to a higher gear, moments before, the ticking goes away and and then comes back as it shifts, up or down a gear, it doesn't matter.
I'm a brand new Chevy Owner, never owned a full size truck before, bought a service body with a Lincoln Ranger welding machine with 50' of leads and O2, Acetylene cylinders complete with hoses and gauges all for $1750 (I love the truck, my Ford owning family would skin me alive reading this.) I want to keep it for a long time, any and all help would be great. -New Chevy Man

 

Check your bellhousing bolts, I have the same issue with my 89' K3500. I found my bolts had backed out on half the housing making my flex plate tap on the housing. I just had to tighten them up. Unfortunately I noticed I have a crack in the housing and now I need to find a new tranny or at least the housing. I hope you have better luck than me.