740 & 760 LH2.4 Flywheel

If you could fit the tone ring ( correct name?), from an LH2.4 auto trans Flexplate to a dished flywheel without holes by lathing the flywheel down and then pressing the ring onto it?

Any input is helpful



  • I very much doubt that the holes would be deep enough for it to work. The tone ring is at a guess only 1.5mm thick which would become your hole depth.

    With a flex plate and a dished flywheel in hand, a good machine shop should be able to figure out making stock style lh2.4 holes.

  • what i mean is a small lip to press the ring onto and have it lathed below the tone ring at the correct depth so it looks like a step basically

  • 1971_144GL1971_144GL (@1971_144GL) Launceston, Tasmania

    I have been looking into this, but hard to get time lately.

    Yes I think it's possible, but not quite as straight forward as it immediately looks. This and other gearbox fun was intended to be a summer project, but setting up the workshop is taking it's time.

    I do think that merging with the flat flywheel is probably easier if you don't need the dished flywheel. Do you need the heavier flywheel?

    The shape of the ring, where it is welded to the ring gear, makes it more difficult. I also don't think that just pressing it on will be safe. It looks better to keep the auto flywheel intact and machine a flywheel to fit in its centre to match the contour. The bolts into the crank can then sandwich the two parts, and the there is no potential for a timing angle error from a machining error, as could happen when modifying a flywheel. I will post what I discover.

  • ^ My goodness, you have been busy!

  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress

    If you have a lathe, why not just use it to mill slots for the sensor and avoid all the other stuff? Measure and mark the flywheel, mount the flywheel on a shaft on your tool post, etc. It's a bunch of time spent in setup but it wouldn't cost much and you'd be able to make more.

  • 1971_144GL1971_144GL (@1971_144GL) Launceston, Tasmania

    Hi James, I also have an accurate English mill and rotary table, so the notch in the rim of the flywheel method would be tedious but straight forward. The tool post dividing method might work, but for me it would rely on manually sighting each angle on a small diameter marking ring at the tool post, so by the edge of the flywheel any error could be greatly magnified I suspect. I have a very accurate dividing plate, but I save this for work that is fine tollerence. A cheap one from eBay could probably work well enough l would guess?

    My idea here is that it should be possible for a person with a fairly simple setup to merge flywheels. There is a bit of talk about around errors in machining the sensor gaps. I would avoid this by this method, and after messing about the first time to get dimensions, future versions would be around an hour to machine in future at a guess. After surface grinding and balanceing, it could still be an economical solution, and slightly lighter than a flat flywheel. But I am no expert and this may just be a crazy experiment I have dreamed up for my pile of Volvo "treasure". If my beloved doesn't call Simms metal first.

  • Went into a machine shop and they quoted me $300

  • The tone ring is pretty well on there and might need a tack weld and then a balance?

  • Hey mate

    i actually merged a ring gear from an auto onto a flat flywheel on my 240 on the weekend when doing a turbo and computer conversion.

    i thought that I could cut the ring gear and bolt on the it on with pressure plate and clutch. Unfortunately it will push the pressure plate back about 2mm because of the ring gear will cause the clutch to loose abit of pressure.

    After I welded the ring gear to the flywheel but crank position sensors needs to be relocated back about 40mm with washers.

    Also the bellhousing of the gearbox needs to lightly massaged because the ring gear hits the bellhousing.

    its rough but it will work

  • This has to be the most turbobricks thread on all of OzV. Well done.

  • turvolvo_kidNav (@turvolvo_kid) Lismore NSW
    edited March 12

    Unlike the Witchcraft above, I think that this should be fine as it has been cut just on the edge, whereas yours has part of the flex plate spacing it out therefore i don't think it will need a "Swedish Massage" to make it fit. Edit* just checked and it does fit.

  • Hard to tell but how many mm of clearance between the ring and the flywheel?

  • Just checked and it does fit. Has the same clearance as the drilled flywheel so around 8mm if i remember correctly.

  • Your main issue is just alignment as with lh2.4 there is no adjustment that you can make via the distributor for ignition timing

    There are some wires on the ezk you can ground out or power to adjust things if your off by 1 or 2*

  • turvolvo_kidNav (@turvolvo_kid) Lismore NSW
    edited March 20

    Ok well, i don't know what happened inside my head when i replied last. I got more taken off the flywheel and it is now at 8mm clearance

  • How much weight has that saved?

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