Results 1 to 7 of 7

Thread: 121 diff

  1. #1
    Junior Member
    Join Date
    Apr 2009
    Location
    auckland
    Posts
    10

    121 diff

    Hi - what are the chances of the 121 diff coping with 200 bhp non turbo 13b set up. I've been told that it's a 24 spline (12A and piston) rather than 28 (RX5). Cheers for any thoughts.

  2. #2
    Senior Member
    Join Date
    Nov 2007
    Location
    Queensland Australia
    Posts
    159
    I assume your contemplating the diff for your wagon?

    If you are I can advise the original diff WILL cope with that hp.

    My 13B powered Luce (1800) Estate was dyno'd at 187KW atw on the original diff. My intention was to replace it when it broke but it survived (without any sign of protest) for the few years I had it.

  3. #3
    Junior Member
    Join Date
    Apr 2009
    Location
    auckland
    Posts
    10
    yep - starting to look around for parts. I wanted to switch to disc rear, and 4.1 ratio as starting point (121).

  4. #4
    Junior Member
    Join Date
    Apr 2009
    Location
    auckland
    Posts
    10
    how did you find the gearing on the original diff with the 13b installed?

  5. #5
    Senior Member
    Join Date
    Nov 2007
    Location
    Queensland Australia
    Posts
    159
    Quote Originally Posted by robj
    how did you find the gearing on the original diff with the 13b installed?
    Just perfect, I used an RX5 5 speed and made up a one piece driveshaft to suit.
    There wasnt many cars on the street that could keep up with it in 1st and 2nd gears. Twin 36IDF webers gave terrific torque and original rear drum brakes seemed to work just fine also.

  6. #6
    Member
    Join Date
    Feb 2010
    Location
    Melbourne
    Posts
    43

    Re: 121 diff

    Quote Originally Posted by robj
    Hi - what are the chances of the 121 diff coping with 200 bhp non turbo 13b set up. I've been told that it's a 24 spline (12A and piston) rather than 28 (RX5). Cheers for any thoughts.
    24 spline centre/axles will just cope but don't thrash it because you will very quickly find the limitations of it. If you weld up the centre expect to break an axle.

    28 spline centre/axles will easily cope.

    The issue with these diffs is more about finding the right gearing. The smaller 24 spline centres have the better gearing (4.1 and 4.4 available) while the 28 spline centres are limited to 3.36 and 3.9.

    I have now seen that you can machine the 28 spline hemisphere to take the smaller crownwheel of the 24 spline centre and package that into either carrier and then run the 28 spline side gears etc for the best combo of strength and gearing.

    However its alot of mucking around with a standard diff when the trend toward hilux diffs is well known.

    /my 2c

  7. #7
    Junior Member
    Join Date
    Apr 2009
    Location
    auckland
    Posts
    10
    Thanks Aaron. Hilux diff would be have to be shortened to fit which would put the price of the package up. Plus it's non disc. Hear what you're saying about the strength though.

Similar Threads

  1. KGC/Z Diff options?
    By wookieballa in forum Datsun/Nissan Garage
    Replies: 7
    Last Post: 08-09-2012, 06:44 AM
  2. Diff ratio?
    By Toyohead in forum Toyota Garage
    Replies: 1
    Last Post: 07-21-2012, 07:43 AM
  3. 3.73 vs 3.91 diff which is better
    By boilerman in forum Toyota Garage
    Replies: 8
    Last Post: 10-10-2011, 09:00 PM
  4. trade welded diff for stock diff mx87 cressida
    By xsquintsx in forum Toyota Swap Meet
    Replies: 0
    Last Post: 07-01-2011, 05:17 PM
  5. diff options
    By liquid51 in forum Toyota Garage
    Replies: 3
    Last Post: 02-01-2011, 09:09 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •