Allison Trans Trouble !

#1
I have a 2002 Chevy Silverado with the Duramax engine and Allison trans.I just turned 38000 miles and what appears to be a trans problem has acurred.When driven real easy the trans seems to shift properly.It's when I jump on the gas @ 30 mph or 80 mph doesn't matter,it seems to down shift but will not shift the rpm's will increase but the truck will bog down.If I let off on the throttle and procede real easy it will shift properly again.
 
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