i seem to remember a long time ago reading somethign on this , but cannot find it at all anymore.

what is the difference between s4 and s5 auto tranys? i seem to remember hearing somethign like one is vacume kick down, vs electronic kickdown? i dont know if this is accurate though.

reason i ask guy is looking for a trany for a 90, but i have one from an 87 not sure if they would be compatable.

thank you!

 

s4 is 4n71b the s5 is RE4R01A

the s4 is basically an overdrive version of the 3n71b found in the earlier rx's and mazdas
( which is a rip off of the c4 )
these can be retrofitted with relative ease to other cars without need for complicated electronics

the s5 unit,, not,, it has a funky electronic shift cable lockout mechanism that can lockout T bar movement

i am not the pro on them but the s5 looks like you need to think about the electronics if fitting into other cars

i would recommend you wait and purchase the correct box

 

The S4 does not come equipped with a computer to control the transmission while the S5 does.