Synthetic gearbox oil

Discussion in 'Mech Tech' started by JT1, Oct 3, 2018.

  1. JT1


    Time to replace the oil in the gearbox as I have no idea how long its been since it had a change. No idea as well as to the condition of the box as it's not the original and was replaced by the PO.

    Having experienced the difference synthetic oil can make to a gear change (especially when cold), I'm tempted to try it.

    This looks promising as its safe with the yellow metals in the box and is GL4/5 MT1 rated.

    Never heard of Westway so has anyone used it with any success or otherwise?

  2. A long time ago I had a early mx5 and they had a reputation for a stiff box when cold (snigger;)) and red line fully synthetic was the recommended cure. It worked when I used it but it's now really really expensive.

    I've been looking at the same stuff tonight as my car needs an engine oil change and I might treat it to box oil, especially as it's done 160k on what's probably the original oil...
  3. JT1


    It was my son's MX5 that also had a stiff box when cold :)
    garethpuk likes this.
  4. That's enough stiff boxes, lads.
  5. It's when you get a tight box that you have to choose your lube carefully

    Oh and I use Castrol aswell

    Sent from my FIG-LX1 using Tapatalk
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  6. Castrol is a brand, which oil type do you use?
  7. Same as you've quoted Castrol Syntrans Transaxle 75W-90

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    77 Westy likes this.
  8. JT1


    Seems Castrol is the winner here.
    I've been put off Castrol oils when 'as a lad' hanging around the local motor mechanic's hoping to be allowed to work on a car , he dismissed the Castrol rep with a cheery 'Wouldn't oil me pushbike with it'. Have subsequently viewed all Castrol products with suspicion. I was a Duckhams man....
    Funny how impressionable you are when young...:rolleyes:
  9. Pay attention how much oil will come out, very likely to be too little. If its the case there might be some damage to pinion bearing thrust surfaces, first gear and the mainshaft bearing.
    Last edited: Oct 4, 2018
    Mark Darby, JT1 and snotty like this.
  10. JT1


    Just over 2 litres came out. The warning sign was no oil came out when I fitted a reversing light switch last week. The drain plug had some very fine, almost graphite, gunge around the magnet but no big, horrible metal bits.
    Just under 3.5 litres went in and a noticeable improvement in engaging and changing gears now there's the proper amount of oil sloshing around...
    The synthetic stuff is incredibly slippery and a pain in the a###e to fill with a half litre syringe.

    Changed the engine oil whilst scrabbling around there too. Used Rye Oils 20w 50 - no idea if its any good, will have to wait and see but was tempted by the 1500 ppm of ZDDP content.
    snotty likes this.
  11. thats more then usual i seen one that had less then a cupfull
    Valveandy, JT1 and snotty like this.
  12. Now might be a good time to remind anyone reading this considering an oil change to make sure they are able to remove the filler plug BEFORE draining the oil.

    It really spoils your day when you realise you can’t put any oil back into your gearbox until you sort a seized/previous-owner-mangled filler plug!
  13. I usually require a bit of give!
  14. JT1


    Good point. After reading some of the horror stories on this forum with unmoveable filler plugs, I soaked it with WD40 for a few days beforehand and it came out relatively easily though not as easily as the drain plug admittedly!
    I used a 0.5 litre (as it turned out) syringe to refill it which was a pita as it meant 7 trips underneath the van to fill it up and the synthetic oil is remarkably slippery. Next time (?) I'll try something like this

    Attached Files:

    Mark Darby and Day like this.

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