DDK - Die Deutschen Klassiker

Recently changed my gearbox oil as I have no record of it ever being done, I’m glad I did as the fluid was due a change.

I used 80w-90 gl5 morris oil as recommended.. I’ve been out for a few runs since and I’m noticing that the changes arnt as slick as they used to be, I’m definitely getting grinding which I didn’t get before.

Not many suppliers of swepco in the uk, but all threads keep coming back to this oil.. should I just buy the swepco 201 or can someone recommend a good uk alternative. 901 box.

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Subjective but ... many on here (including me) have tried Swepco in the past & found it to be a waste of money.

Just use a good quality EP80 or 90 oil .

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When racing I tried a few fluids but we eventually settled on 1 ltr swepco and 2&1/4 ltr 80/90, obviously mixed, before filling and never had a problem. Found swepco on its own too thick.

Mike Bainbridge always told me to dump the swepco I had and just go with a good quality branded gearbox oil

I think the Swepco fetish comes from Rennlist or Pelican, where they're curiously tribal over oil. Forty years ago when you could do a label in Helvetica Neue and Compacta Bold and stick it on a bottle of whale oil and call it wonder lubricant and you'd only be found out if someone wrote a detailed letter about it in Cars and Car Conversions, then there was cause to be sceptical over oil. Nowadays there are detailed specifications oil has to fall into before it can be sold, and as such Tesco 75W-90 will be just as good as Swepco 75W-90.

I use Castrol EP80-90 (admittedly in my 915) and its spot on.

I think most of the issues with gearboxes are worn synchros/dogs and linkage/shift rod adjustments, not what brand of oil you are using.

I had the same quandry as you when I changed mine a while back but after speaking to a few knowledgaeble folk (including Mike Bainbridge) I eventually decided to go with the Castrol EP80-90, same as Gary used

I think the consensus from most gearbox ‘guru’s’ for the 911/912 gearboxes, is that Swepco is too slippery for the older type gearboxes, and their synchro hubs.

Whilst oil technology might have moved on, the moving parts in old Porsche gearboxes has not, so just use what the Porsche original designed for them. There is a reason EP 80/90 oils are still available and have not been replaced.
I would have thought you would have been better off with a good MINERAL EP90 as opposed to synthetic, which is not ideal for old style Porsche-type synchros, and apparently does not give enough friction for the synchros. Porsche engineers in the 1960/70’s specifically factored in the gear oil to help slow down the synchro's during engagement. Synthetic oils do not help the pieces slow down and cause premature wear. Synthetic might not make the baulk-ring synchros of the 901/915 boxes work well.

If you speak with Mike Bainbridge he will give you an idea what to use. He always recommends an EP 80 or 90 MINERAL OIL

Read this post..............

viewtopic.php?t=71544&hilit=swepco

Thank you for everyone’s suggestions!

It is possible my gearbox is wearing… I’ve ordered some Castrol 80/90 and I’ll give that a go. Surprised how cheap it was..

T100912 wrote: ↑Mon Jul 22, 2024 6:08 pm Thank you for everyone’s suggestions!

It is possible my gearbox is wearing… I’ve ordered some Castrol 80/90 and I’ll give that a go. Surprised how cheap it was..

Box feels great after the exchange!

Good to hear - I'm due a change and have Swepco in mine but was looking to switch back to something more conventional

There is some issue relating to gearboxes which have bronze synchros, which I think applies to the 901. I'm not confident I remember correctly but I think bronze additives in diff oil prevent little microwelds occuring between steel surfacea under very high pressure (i.e. in the diff). However, if you have bronze synchros, the oil's high bronze content is bad for the synchros so you're better off with a low bronze ep 90.

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Been using Motul 80-90 for past few years and can't fault it.