[nxcoupe]

I have broken a 3550 input shaft once. Spec Stage 3(David has it somewhere at Spec, it was still stuck in the disk when I sent it to him). I was running 9.90's with 300 shot on a 306, 28 X 10 slicks. I was going into 3rd when the input broke. I never broke a gear in my 3550, after two seasons running 9's and 10.0's. I don't think that qualifies as luck. I replaced it with a TKO input(I have an extra that is new if you are interested), as all the gears in an old TKO and 3550 are the same.
I went 9.70's with the TKO input and the 3550 internals. It was a reliable trans that worked for two years no problems, hundreds of passes. A great idea would be for you to use a Swarr Girdle, they are 129, work wonders for the thing to keep the input and countershaft from pushing apart and I attribute this to my two years of no problems.