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Play in crown and pinnion

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  • Play in crown and pinnion

    Got more information that may help you , help me!

    The dist between my four wheel studs is 3.75", I'm sure I have the ITAL diff ('92) but not sure what the spacing of 3.75" tells me with respect to the ratio etc of the diff as I am a newbie on the list.

    I put the car up on my hoist and put the parking brake on, I rotated the U joint in front of the crown/pinnion (diff) and I got about a 1/2" play, nothing to worry about pretty typical for this type of set up (I think). BUT, when I put a screw driver in to the U joint, and applied a bit of force I could get the U joint to move, or more like "snap" yet ANOTHER 1/2" till it "bit" in to the hubs/wheels to go forward and heard what I can only think if I was driving the car the "clunk" at the hub end as I've talked about before.

    I'm as sure as I can be this is why I'm getting the clunk, but what is the cause?

    Thanks, pat

  • #2
    Yet a bit more info. I took the drive shaft off the diff, the main nut is tight. But when I put a socket on it and push it further than the normal slop allows the axle nut (at the wheel) will turn the same amount I push on the socket until of course it stops, giving me my "clunk" when driving. The other side (Passenger, on a RHD) does not move at all. Any ideas what the heck could be wrong? Diff guts I'm guessing.. but is it repairable or do I need a new one? (Another thread coming if so).
    Thanks, Pat


    • #3
      You may find better information on the the ITAL diff on Blatchat, the UK Lotus Seven website as they have a lot more solid axle cars in their membership.

      There should be virtually no play in the U joints themselves. If any replace them. An easy job especially if you have the drive shaft out.

      The differential crown and pinion can be changed from stock so I don't think the stud spacing will tell you the ratio. It's easy to figure out. Rotate a rear wheel 10 times while counting how many times the driveshaft yoke goes around.



      • #4
        If I'm reading what you wrote correctly, I hope that nut you checked was "tight" is staked or uses a solid spacer. That nut is generally torqued to a specific amount in order to set your pinion bearing pre-load using a crush washer.

        It's not clear what 1/2" means. You're turning something, so isn't this an angular displacement, not distance?.

        I'm really struggling to understand what could cause a clunk inside your diff. It's just 2 a pinion and ring gear. There's not really a whole lot to go wrong there. Even the differential itself is just worm gears. Usually if something does go wrong, it has to do with the backlash of the gears and you'll hear more of a gear whine than a clunk. Have you determined if it's a limited slip yet?

        Are you sure it's just the diff rotating and the axle itself isn't moving?

        I agree with doug about replacing the u-joint. Think about what stands between you and that driveshaft...


        • #5
          I kinda wanted to leave this for the winter, but it was bugging the heck out of me so I pulled apart the suspected rear hub area. I found the problem... the woodruff key slot in the one hub is worn like crazy, it's that simple! Could anyone kindly identify what the rear axle is I have so I can source parts if I can't get a new slot cut? IS this an Ital diff and if so what cars does it come from do you know? Thanks, Pat

          Lotus_Diff 002.JPGLotus_Diff 003.JPGLotus_Diff 005.jpgLotus_Diff 006.JPGLotus_Diff 007.JPG


          • #6
            I would email Caterham in the UK for ID and parts.

            Also check Blatchat. I seem to recall that the Ital rear end is getting hard to source. Axles may be easier.

            Shipping form the UK is not that bad $ wise and you get the parts in a week or less if they ship by Parcel Force.


            PS: Did you check the other side too?


            • #7
              Question on the Caterham dealer in England. They say on their web site that they forward questions to the local dealer in the area, is this so as we have one in Canada? I'd like to deal directly with the UK Caterham for some stuff.

              Just an update, I have made a custom key, and inch longer that is now biting in to the good more inner, part of the key way. This will do me for the rest of the summer. A suggestion was made to take the axle and hub to a machine shop and have a wider key way made.
              Thanks, Pat


              • #8
                I don't know about now but Caterham UK has sold me many parts. Usually Caterham USA did not have them in stock, also Caterham UK was cheaper including shipping.

                Does the longer key fit in both the hub and the axle? If not it may be bending in the wider slot.

                A wider key should work fine. I would not try to weld up the worn part as it may warp the axle.