i have an S5 turbo that only grinds in third and only heavy load and i believe it to be a bad synchro so i decided it be easier to swap out the tranny. so here is my question, someone in my area is selling a s4 turbo tranny for $100 and i wanted to know if there is any major differences between the S4 and S5 turbo trannies and which is better built and for a little side note can an FD tranny be applied to an s5 turbo???

FD trans, can fit but its a TON of work, as you have to fab a new mount, get a new clutch etc etc.



S5 is a little better, but not much, and the S4 will go right in, except the trans mount is different, so S4 mount, with S4 trans and S5 mount with S5 trans.

what about gear ratios and such all the same??

Stock Transmission Ratios



Application 1st 2nd 3rd 4th 5th



74-76 RX2, 3, 4, Cosmo, P/U 3.683 2.263 1.397 1.00 .862

77-78 RX3SP, 4, Cosmo 3.380 2.002 1.390 1.00 .791

79-80 RX7 3.674 2.217 1.432 1.00 .825

81-83 RX7 3.674 2.217 1.432 1.00 .825

84-85 RX7 12a 3.622 2.186 1.419 1.00 .758

84-85 13b GSLSE 3.622 2.186 1.419 1.00 .807



1986 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .711

87-88 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .697

89-92 Non-Turbo w/o LSD 3.475 2.002 1.366 1.00 .697

89-92 Non-Turbo with LSD 3.475 2.002 1.366 1.00 .756

86-88 RX7 Turbo 3.483 2.015 1.391 1.00 .762

89-95 RX7 Turbo 3.483 2.015 1.391 1.00 .719



Miata 3.13 1.833 1.303 1.00 .840