Announcement

Collapse
No announcement yet.

120 diff fitted in 90 series 3.4 Manual car

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • 120 diff fitted in 90 series 3.4 Manual car

    I posted as below in the 120 forum - now adding it to the 90 series forum

    I have a 1999 3.4 manual with a 4.1 diff. The car has served me well having survived a rollover and many other off road adventures. Of late the rear diff started to make terrible noises and fearing a seize up I disconnected the rear tailshaft and now drive front wheel drive only - its a pain as no LSD so she slips easily on wet ground. Turning the input pinion for the rear diff feels like a bucket of gravel.
    So I searched out a diff on Gumtree. (beware their are liars out there) A full rear end was on offer supposedly for my model (2002 3.4 RV manual). I went to pick it up and could not turn the pinion due to the brakes being seized up. I was doubtful, but the seller was adamant it was from a 2002 3.4 litre car as indicated.

    Got it home and on stripping found that it was from a 2003/09 4 litre with a ratio of 3.7:1, not 4.1:1 as mine is. In fact the whole assembly is wider as the 120 series has a different track - axles are 30mm longer. But I thought if I could use the diff and disconnect the front drive shaft I would have a usable car in RWD - better than FWD as rear has a limited slip diff, it would still be quite capable off road.

    So I pulled out the old diff and fitted the replacement. All seemed good until I found that the tailshaft yoke on the 120 series has 65mm hole spaces as opposed to 60mm on the 90 series.

    So the question is, will the splined yoke from a 120 series tailshaft fit my tailshaft?

    My question has been answered. Went to a wreckers and checked out a 120 tailshaft. Same spline pattern.
    Now I have a 90 series with a 41/11 (3.7) diff. Runs well. 10% reduction in revs at any particular road speed.

    Will have to check speedo against GPS o I know how fast I am going.

  • #2
    Thats one way of upgrading.
    Do you think you could fit one in the front too?
    And is it just the 120 diff gears you are using in the rear? Not the short shafts/housing etc?

    Comment


    • #3
      Yes speed is done from the end of the transfercase so you will need gps to give you speed. I think in the newer models it went to wheel/abs sensors for speed

      Comment


      • #4
        Originally posted by MikeyB View Post
        Thats one way of upgrading.
        Do you think you could fit one in the front too?
        And is it just the 120 diff gears you are using in the rear? Not the short shafts/housing etc?
        Probably could do the front, but my car is not worth it.
        The rear housing is all 90 series including the axles. Only the diff was changed out. There is a tiny difference on how deep the axles fit into the spline cases in the diff. They are about 5mm from the bottom, whereas on the original diff they sit about 1mm from the bottom. Still plenty of meat for the axle splines to seat.
        Car is very quiet and smooth. Am using 4th much more now than previous (I would use 5th in 60kmh zones before). I find 2nd gear a bit high and must not let the speed drop too low if I hold this gear. Otherwise it's great!

        Comment

        Working...
        X