View Full Version : tranny question

08-29-2007, 12:50 AM
ok i wast thinking of putting a rb20 transmission on my ka-t does any one know what the ration on this tranny i heard the hold a lot more power than the sr,i already try the sr and i didn't like it the gears where to short for me ,so does any know knows?

08-29-2007, 07:31 AM
SR ratio is too short? SR's tranny is pretty much same as the KA tranny except the bellhousing, both are W71C. SR's 4th or 5th gear might be slightly diff but not by much.

Have you try taller rear end ratio other than stock 4.083:1??

08-29-2007, 10:40 AM
well i try the sr and i didn't like it and i bouth two and they blow up they are not as strong as the ka ,that why i wanna know if the rb20 is going to have the same ration,and they said is stronger,i know the 300zx is more leess the same as the ka i think aliitle longer,i have a j30 rear diff which i have like two teeth smaller than the ka is a 47 and the ka is a 49

08-29-2007, 10:42 AM
the rb20 is just swapping the bell housing also

08-29-2007, 11:28 AM
well, after a little research, the 240sx's tranny (KA or SR) - W71C
1st- 3.321
2nd- 1.902
3rd- 1.308
4th- 1.000
5th- 0.759

Z32 300zx (NA and TT is the same) RS5R30A:

1st 3.214
2nd 1.925
3rd 1.302
4th 1.000
5th 0.752

so, the 300zx's tranny is slighty taller in 1st, 3rd, and 5th gear.

08-29-2007, 02:57 PM
the 300zx it will be perfect,it has alitle more top end that a stcok ka one and it a lot stronger

08-29-2007, 03:11 PM
There are a few companies that offer the adpter to use the Z32 tansmission . I would recomend MazWorx they have a package for everything from the tranny housing , shifter , driveshaft ( lighter and a one peice ) and Z32 transmission support . Again there is a write up on the transmission gear differences and the transmission strength on here some where .

08-29-2007, 03:13 PM
the j30 diff is a 3.96.....i had one of these diffs in my setup and i hated the diff.way to tall of a gear...went to the r32 gst diff 4.36 and love this diff.
S14 ka and S14 SR trannys are the same 1st - 4th....5th is one tooth smaller......I have blown up 1 sr tranny and 4 ka trannys....take my word go with the 300zx tranny and adapter kit from maxworx and be done with it.

08-29-2007, 08:43 PM
yeah i wanna do that but i don't have 1000 dollars right now,and if i could find out the gearing on the rb20 all i have tio used the my ka bellhousing and that it

08-29-2007, 09:08 PM
The RB20 is a W71C.
The KA24 is a W71C.
The SR20 is a W71C.

they will all fail at the same power levels / abuse

how long depends on their previous lives.

ive broken 3rd gear in a transmission, swapped it out in 10 minutes, broken 3rd gear on that one on THE VERY NEXT LAP, swapped THAT one out in about 10 minutes, and broke the THIRD transmission in less than an hour on the second lap in it.

so, umm. W71C's suck.

08-29-2007, 09:13 PM
damn how much power are you making

08-29-2007, 09:41 PM
the car was making around 410 at the wheels, and 370 torque.

08-30-2007, 01:37 AM
damn and they blow like that easy,i'm making almost 300 and nothing yet and i power shift also ,soon i'm going to be making like around 450,so let' see