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Castrol Gearbox Oil in Citroen box

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🖐️ It`s that time again to change the gear oil in my Esprit S3 and Turbo HC.  I have read a couple of older threads of what official oil to use in the Esprit and what type a specialists recommend.  Castrol have updated their range within the last year or two and have several to choose from.  The most important in my opinion is firstly the words Transaxle and Manual.  Maybe I`m reading too much into it but hopefully my mind can be put at rest so I can sleep easy tonight!

The same official recommendations used to appear for the Citroen and Renault boxes to use Castrol Manual TAF-X oil.  This is SAE75W-90, API GL4/5, VW 501 50 (as written on the bottle I still have).  The recommendation by Lotus circa 2012 (from another thread) was that Syntrans Transaxle 75W-90 oil could be used as the TAF-X was discontinued.  I`m not sure if this was a GL5 or GL4 or GL4+.  When TAF-X ran out of stock Opie Oils stated on their website that Syntrans Transaxle replaced this.  It now states that their Transmax Manual Transaxle 75W-90 GL4+ replaces the Syntrans.  The Transmax Manual is specified as a GL4+ and EP (extreme pressure) performance.  It is also to VW 501 50 as per the TAF-X.  The service manual and booklet recommends API GL5 however.  I imagine this is because there are EP requirements for harder metal parts mixed with softer metal components.  I have not had any problems for the last 15-20 years or so using TAF-X or Syntrans, so I must be doing something right!  When I do a search on Opie for my car it comes up with Transmax Universal LL 75W-90 GL4/GL5, though not the same VW approval.  Not sure what LL means.  Long life maybe.  Another thing I have noticed is that these oils are about twice the price they used to be, but these days you can`t do much about that. 

There are recommendations to overfill the gearbox to 3L for better lubrication for the synchro and needle bearing 5th gear on the primary shaft, rather than 2.25L, though I have never done this, I have read this can cause the oil to foam creating oil starvation.  I have gone a bit over the norm bolt hole level in the past, nothing too much.  I have also been told in the past that the gearbox doesn`t need that much oil to run, so not to worry if it leaks slightly from the rear plate.  I am open to doing whatever is best for my gearbox.    I may be reading too much into this and may have answered my own question by now.

I know there are different additives for a GL5 that can affect the softer metal parts causing potential corrosion, and going the other way with GL4 may wear out other parts faster.  This is all speculation from my point of view and I`m just a user of the product. The GL4+ seems like the right compromise? I was going to buy the Transmax Manual Transaxle stuff and be done with.

Cheers, Dan


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I have used Redline MT90 in the past adding 3 quarts but find it really thin so want to try something else this time (Building two gearboxes currently).

I’m happy to try Castrol as like their engine oil if it works well?



Do or do not, there is no try! 


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I read many years ago that the chemicals in synthetic oil causes the rubber oil seals to swell so reducing leakage. Certainly when I first put Mobil synthetic in the Renault box of my Stevens' Esprit the drip that had always been underneath disappeared. :thumbup:


John W

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Most synthetic and mineral base oils actually tend to cause rubber seals to shrink so appropriate rubber swell additives are added as part of the formulation in quality oils to counteract this.  "High mileage" engine oils or supplementary lubricant additives have additional swell additives to help counter wear on seals by additional swell to minimise leakage from places like the rear main seal 




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