164 to 240 Diff Center exchange

Hi all,

I would like to swap the diff center on my 1974 164 (3.54:1) for a 3.91:1 from a 1976 245. Will the 3.91 bolt straight into the 164 diff housing? Does the pinion have to be changed, and are the splines the same on the drive shafts? I would appreciate response from anyone who knows or who has done the swap before.




  • Firstly, any ratio change requires the pinion gear to be changed. They are a matched set.

  • SpacSpac @Spac Canberra-ish.
    edited February 10

    Should work. Both are basically Dana 30 diffs. There's a change in the crownwheel offset that applies to Dana diffs but not in Volvo diffs (IIRC).

    Axle splines are the same (27-spline).

    Also be aware that later 240s have a slightly larger diff (1031 vs the older 1030 in Volvo speak). The change over was a bit higgledy-piggedly through the early 1980s. You can't use 1031 ratios in the earlier cars.

    If the ratio you want comes in a 140, then just buy a whole 140 diff. far less effort to swap a complete diff than to swap the ratio and set it all up correctly.

  • By the sound of it leave it alone. Another option I am thinking of is modifying the 245 391:1 diff to make it fit the 164. Shouldn't be too hard I reckon. And the other option again is indeed getting a 140 diff. Not sure if they had the 3.91 ratio. From memory they were more 4.11.

    Thanks for the response.

  • SpacSpac @Spac Canberra-ish.

    240 diff is slightly narrower than a 140/164 diff. Can't remember the measurement though, sorry.

  • Keeps getting harder :/ I'll have to research that one or maybe do a quick check with the ones I have here.

  • Note: I haven't done this, I just read a lot.

    IIRC the breakpoint for 1030 Volvo diffs is 3.54:1, so you should be able to change the crownwheel and pinion matched set from your 245 in your 164 (they are both 1030 type diffs), and use the 164's original carrier.

    AFAIK 140 diffs were either 4.1:1 or 4.3:1.

    The 240 diffs are shorter and have different trailing arm mounting brackets to 140/164 diffs.

  • 1971_144GL1971_144GL @1971_144GL Launceston, Tasmania

    You can buy a range of new gear sets in different ratios for these diffs as the Dana diff center is widely used. Setting up a diff takes some knowledge or willingness to invest time learning, however it may be the best way if you want a specific ratio. The new gears will need to be fully setup, and new bearings and shims are a good idea. They are relatively affordable if you fit up yourself, and it is getting hard to find good diffs that old.

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