The T56 is a strong tranny on its own. The problem is the clutch/ hydrolics. The "mushy" pedal feel is from the clutch system. Its either the stock clutch getting worn (they are self adjusting and can only adjust so far) or the hydrolic system (that needs to be upgraded to a 01-02 setup). You also have to do the "drill mod" for the master to keep up. That was a stupid idea on GMs part. Ive put up to 700 RWTQ on a stock tranny spraying a 200 shot at 3000 RPMs and my latest was ~600 RWTQ with my turbo setup (but the tranny was far from stock). Also, you NEED to wrap the hydrolic line from the master to the slave with heat wrap as it travel right over the header/ exhaust.

The stock tranny does have a weak point or 2. One is the 3-4 shift fork is aluminum which will bend if shifted hard causing the tranny to pop out of 3rd gear. The fix is to replace the aluminum fork with a steel one. The next is that the earlier T56s used paper blockers (I think thats the name) and they wear fast and arent compatiable with synthetic fluid.

If you can find a good clutch and good hydrolics, the T56 is a damn nice setup.