Repairing rust on gearbox shaft
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  1. #1
    Fellow Frogger! IThompson's Avatar
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    Default Repairing rust on gearbox shaft

    I have bought another R12 for parts which also came with an R18 gearbox and a pair of drive shafts.

    There is considerable surface rust on the gearbox splined output shafts. Should this rust be removed before use (i assume yes) and what is a good method of removal. Emery paper and a lot of patience?

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    Likewise the splines on the drive shafts.

    On a side note is the R18 box going to fit in an R12? Or are the mounts too different?

    Ian

  2. #2
    1000+ Posts jo proffi's Avatar
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    When i had a r12, they were doing the 5 speed conversions with r18 gear boxses so i'd say yes it does fit, but I'd assume a fair bit of fabrication will be needed.

    Re splines, I've always just brushed off the rust with a wire brush and applied a grease to the splines.

    Being a renault, they should be covered in gearbox oil fairly soon after being installed.

    Jo

  3. #3
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    Is your renault 12 automatic? Transmission hump for auto is bigger than the manual one and 5 speed will fit in auto car without modifying hump. You'll have to make your own mounts. Are the driveshafts you have shortened? Because the 18 diff is wider the shafts need to be a little shorter than standard. What Motor are you running? If it's a 17 motor 18 bell housing will work (although clutch arm is a little longer) but if its a 12 motor have to change bell housing and input shaft. Also, you'll have to make gear linkages.

  4. #4
    1000+ Posts renault8&10's Avatar
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    Do what Jo suggests but for future reference on rust removal, for readily portable pieces google use of molasses solution for rust removal.
    I think there might have even been a thread on here as well?
    KB


  5. #5
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    The next stop after the output shafts inside the gearbox is the diff carrier bearings. If the gearbox has been out in the weather for some time, or has been pressure washed without the driveshafts in place, the bearings may have been contaminated by grit/moisture etc. Whilst the surface rust should come off relatively easily, bits of grit and rust could contaminate the bearings leading to a noisy diff. So, to avoid all that, and make the output shafts easier to clean, it is best to split the gearbox and replace the diff carrier bearings to be on the safe (and quiet) side.

    Also note that there are two types of gearbox, the early 18GTS with a Type 395, and the late 18GTS with an NG series 'box. Both have different gear lever methodologies, so it is best to find the matching bits to suit.

    One other thing worth bearing in mind. The 18GTS gearing is quite tall, I'm not sure if the early pre-1.4 Sierra 12 motor would be best suited to the gearing. I'm guessing in overdrive top it wouldn't be much fun. The best five speed would be a 365 from a 17TS/G, but those are quite (very) rare. If fitting the 18GTS 'box, you would be best also fitting the 18GTS motor, then the fun starts with modifications, vented brakes etc........

    And as specified above, unless it is an auto bodyshell, the hump in the floor of a manual trans 12TL/GL (as opposed to a 12G!) won't clear the rear of the 'five speed 'box, then also the various bellhousing/input shaft permutations........
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    Fellow Frogger! IThompson's Avatar
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    Thanks,
    Looks like i made a mistake in buying the gearbox. I will store it. Either it will come in useful or someone else may need it.

    I wrongly assumed that the r12 and r18 were more closely related.

    The synchro on 2nd in my 12 gearbox is worn and it is difficult to change without crunching. I thought the other gearbox could be a replacement until i fix the first one.

    I have a gearbox in my second car. I will have to look at removing that one instead.


    Thanks

    Ian

  7. #7
    COL
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    Quote Originally Posted by IThompson View Post

    The synchro on 2nd in my 12 gearbox is worn and it is difficult to change without crunching. I thought the other gearbox could be a replacement until i fix the first one.
    Sounds like the energiser spring on the 2nd gear synchro ring is broken, this is a common fault with these gearboxes.

    Its a fairly big job to fix, you need to spit the gearbox and remove the bearings and gears off the secondary shaft. I'm not sure if new springs are available anymore?? but I have used second hand ones before.
    Regards Col

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    Changing the gearbox oil for Castrol VMX 80 is worth a try. Incorrect gearbox oil causes just such a problem. If not too much damage has been done you may be lucky. The new oil will take about 150 - 200 kilometres to take effect. The problem relates to a chemical that attacks the brass syncro's in these gearboxes. There has been many pages written on this subject on Aussie Frogs previously.

  9. #9
    Too many posts! JohnW's Avatar
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    Quote Originally Posted by COL View Post
    Sounds like the energiser spring on the 2nd gear synchro ring is broken, this is a common fault with these gearboxes.

    Its a fairly big job to fix, you need to spit the gearbox and remove the bearings and gears off the secondary shaft. I'm not sure if new springs are available anymore?? but I have used second hand ones before.
    I got some from Ken at Caravelle a few years ago for the R8 - a 10S box in my car. Same as R12 I presume. They aren't shown on Mecaparts catalogue. Chase up the gearbox folk - call Colliers perhaps, Dauphproto on this forum. I'd be surprised if you can't get them as they surely do break, sometimes with catastrophic results. But they aren't shown on the usual sites I get parts from.

    Brave to use secondhand ones Col. Lot of work....
    JohnW

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  10. #10
    COL
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    Quote Originally Posted by JohnW View Post
    I got some from Ken at Caravelle a few years ago for the R8 - a 10S box in my car. Same as R12 I presume. They aren't shown on Mecaparts catalogue. Chase up the gearbox folk - call Colliers perhaps, Dauphproto on this forum. I'd be surprised if you can't get them as they surely do break, sometimes with catastrophic results. But they aren't shown on the usual sites I get parts from.

    Brave to use secondhand ones Col. Lot of work....
    I was working on the principle that if the energiser spring looked in good condition and had lasted for 30 years it would last forever
    Regards Col

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