700 R4 noise

[speedracer]

Hey guys well after only 10 or 15 burn outs my El Camino's trannie is making a clicking noise in first gear only.  It still seems to shift ok but as soon as it down shifts in first then starts the clicking.  If it was a front wheel drive car I would say it sounds like a CV boot problem but of course the sound is coming from under the floor board.
The trannie was bought and installed by my speed shop that has done all the work on the car.  I was told the trannie was beefed up with corvette servo's etc for hot rodding and should handle 400 hp plus.  Even using nitro, I was told that it would handle it, but I have not sprayed it from a dead stop and only 4 times but traveling 50 or 60 mph.  I must say using nitro really made that 350 scream!  Now the trannie is 8 months old and the shop says its still under warranty of the guy that built it, so next week I'm scheduled to take it down to the shop for them to remove it and send it off for inspection by the builder.  Now the speed shop I pretty much trust but this guy who knows!
So thats whats happening in my world.  Any advice/suggestions/comments or Money I can borrow!! LOL
Thanks, johnny
ps  The rear end gears are 4:10 ratio

[Crosley.In.AZ]

clicking in first gear only?  i'd say the rear planetary unit has a problem.

often the torrington bearing in the rear planet chews it's self up. the roller bearings get in the ring gear teeth .  then they click , break,  shatter parts and pieces