just as it says is it possible to change those gears in the auto tranny? any help welcome



04 sunfire auto, mid 15's n/a, and still going

I would also like to know. 1st and 3rd could be a lot better.

Looking at the TranStar catalog, no you can not change the 1st & 3rd gears.
They do list three differentials, but the don't list what the gear ratios are, just the sun gear tooth count(34T, 38T and 42T). I would suspect that the lowerer tooth count sun gear would be a lower(numerically higher) gear ratio, as with the 3T40/TH125C 3 speed.
I also noticed that there is no listing for the drive chain gears, again as with the 3T40, which could also change the overall effective gear ratio.
The 4T40E's VSS/Speedometer pick-up is also drven off the gear ring on the differential(same as the 3T40), so changing the differential won't affect the speedometer or the VSS.