I've got an 81 z28....i know what ur thinking not the same body style...but you guys prob know more about somethin that my 2nd gen brothers don't...and that is the th700r4...i've heard some of you 3rd gen guys downgrade it but you just don't know what its like to not have od...my question is about the gear splits... my camaro has a 3.23posi in it now and i just put the tranny in...i can drive it for awhile cuz the body needs work....but i was wonderin if any of you have the th700 with a 3.23 posi and i would like yalls input...well heck i'd like input from all yall if you will.. i was just wondering if i should leave it the same or go 3.42,3.55,3.73....i know the th700 has a lower first but will the 3.23's make it run like a dog in 2nd and 3rd or are 2nd and third not split too bad and will it accelerate nice. i've got 375 early hp and nice torque ...only think i need to remember is the large weight difference...thanks camaro brothers i always liked the third gen...lata

 

3.23's will be perfectly driveable behind the 700-R4, in fact many 3rd gens came with 2.73's behind it. With a heavier chassis I'd want to go with 3.42 or even 3.73 gears to move it off the line, but 3.23's will give you better highway RPMs and slightly better fuel efficiency. I'd say stick with them for a while and see how you like them. Gear swaps aren't that hard if you want to change it because you already have a 3-series carrier and posi.

 

Also 2nd and 3rd gears are fairly close togetehr as far as ratio goes....the deep 1st will get you off the line but the RPM drop from 2nd to 3rd is small enough to keep you well within your powerband.

 

i got a 3.27 rear and a 383. and i love it but i am think of going to a 3.55 and thats as high as i would go.
i drove a 305 z28 w/700r4 and 373s (305 was stock)(had 205 70/r15 tires) and that thing was sideways all of first and part way through second.
if it was a third gen id go with 3.55 but since yours is heavier i might even go with the 3.73 not to mention you will kill everyone off the line traction permitting.
you should still be able to get over 120 mph