Can you modify gear sizes/acceleration ratios in a Turbo 400 automatic Transmission?


Asked by Sep 30, 2009 at 06:15 PM about the Pontiac Firebird

Question type: Car Customization

Turbo 400 only has three gears and the first gear gets skipped during a 5000 RPM flooring with a 455 engine.

3 Answers


3rd will still be direct drive so 1st and 2nd need to be sized accordingly. its not like a manual trans with gears. ur best bet would prolly be to go with a 700r4 and fabricate a rear trans mount bc the 700r4 is pretty much the only 4spd auto that isnt electronically controlled so no computer


n check ur rear end ratio it prolly aint helpin either


First gear should not skip no matter WHAT GEAR or TRANS you have in it. Sound like you have a trans govenor problem, or kick down linkage problem. If you floor it both mechanism should start you off in first and if I remember correctly the 400's have a govenor overide which actually will shift the car into second with the gear shift still in the first position. I like the 700r4 JOHN as thats what I have in my race car for the lowest 1st gear that GM made Manual OR automatic. However that being said the trans has to be beefed up to accept that kind of power. The only electronics in the R4 is the lock up converter which in my case isnt there anyway :)

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