Has anyone heard of these coming from the factory with shifting problems? My brother has a new z28, and while driving today I noticed that downshifting from 2-3 took about an extra second, it felt like revving in neutral. It rarely happens, the guy at GM couldn't get it to happen when it was taken in for inspection. Shifting from 1-2 can be very violent too, even when accelerating mildly..

 

you said downshifitng 2-3 i take that to mean up shifting 2-3 the problem could be cause by aa stuck checkball in the 1-,2-3 accumulator housing when these tranny's are put together they use a little dab of grase to keep the checkballs where they're supposed to be so the gasket,plate and valve body can go on correctly or the checkball could be missing entirely but i doubt that

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87 trans am 350 L98 aluminum heads,LT4 hot cam,slp runners,headers,y-pipe,edelbrock base,hi flo cat,air foil,ported plenum,t-5 tranny w/centerforce clutch and a 3.27 9bolt,ads strip chip,relocated iat sensor,hollowed maf

14.10@97mph w/2.01 60'