Chevrolet Repair: ticking something, stop sighn, chevrolet cheyenne

Question
-------------------------I forgot to mention that when i shift the transmission lever into 2 or 1 the ticking goes away,i had the tranny fixed due to a leak with only 120 miles back in 1990 at the dealership.But as i mentioned before the tranny shift perfectly and doesnt burn any fluid.I used a piece of hose to listen to where the noise came from and it did sound like the flywheel area,i tried to remove the flywheel cover but it wont come out due to the exhaust crossover pipe,unless its the transfer case?
Followup To
Question -
Hi there again Van;
         
         if i may pick your brain,a 1989 Chevrolet Cheyenne K2500 with an annoying ticking from what seems to be underneath the truck.All oils are o.k.,the truck begun to tick only when driving at a crawling speed,but once you got to 40 mph ticking went away.Now as soon as you start the motor it begins to tick but again once at 40 mph ticking is gone.I laid myself underneath the truck and it sounded like the tranny,but the shifting and fluid are like factory new.I noticed that the oil pressure gague reads 30-45psi at highway and street speeds,the only weird thing is that if iam booking down the highway at 60mph with 45 psi the gague will shoot past 60psi once i slow down as for a stop sighn or a light.that psi will stay at past 60 for 2-3 minutes and than equalize at 45psi.is this a part of the ticking or entirely something else?

         Thank you
         Tom s.
Answer -
Hi Tom,
Gee...you got me on that one. I don't know why the oil pressure would do that.
Could the ticking be something on the flywheel?

The only thing I can think of that could possibly explain all three things is if the crankshaft is moving foreward or rearward due to a worn thrust bearing and the movement covering a different part of the bearings raising the pressure, and the movement allowing the flex plate to barely contact the back of the block.I had it happen, but it was a soft journal on the crankshaft that allowed my movement.
Try prying the crankshaft fore and aft to see how much play there is.

Van

Answer
Hi Tom,
As for the transfer case...if anything is moving in there, then the truck is moving, unless the transfer case is shifted to neutral. So no tick from there when sitting still.
Same for the U joints. If you are sitting still, they wouldn't tick.
Possibly a valve in the transmission opening and closing, like a relief valve, but trannies are not my area.

Van