could fully synthetic castrol syntrax be cause of my oil leaks

Not sure about that oil but I use Redline 75W-90NS (I think that's the one) on my 328. Once the oil is warm the car shifts fantastically and I don't have any gearbox leaks.

BTW, I think 75W-90 is the correct (factory recommended) weight, at least it is for the 328.

-F

 

If used on a modern F -- it's the wrong viscosity (too thick when warm). You should be using something like 75W90 or 80W90 (whether it's synthetic or non-synthetic).

 

Gearbox oil additives can be pretty harsh stuff. Is it your endplate which houses the speedo sensor which is leaking? That's a relatively easy fix if that's it as that cover comes of pretty easily (drain oil first obviously), the only difficulty is in cleaning the mating surface around the shafts which that plate covers. I suggest using lint free paper towels like shop towels (the blue ones) and lacquer thinner or acetone on the towel. Just my .02.

+1 for the Redline 75/90NS

 

I've always been told to NOT use synthetic in a 308/328 because they cause leaks. I know nothing about it, but I've never used a drop of synthetic, and I still have leaks.

It's a Ferrari, it leaks.

 

Synthetics don't actually "cause" leaks. What they will do is make any small leak already there, a bigger problem.

 

When I had my 308, Tim Stanford used Valvoline racing oil, not synthetic.

 

I'm using synthetic in my 328, Redline like Furmano, and I bet Sherpa23 tells you the same. I have no issues/leaks.

 

bingo!...+1

 

+1

My car had a gearbox leak from new, it was documented in the notes for the first service. But when I switched to Redline the leak became a torrent and I had to do something about it.

It seemed that the factory never used any sealant when putting these together. I refitted the pan (after changing shift shaft seals of course) and the round plate which houses the LH output shaft seal using Loctite 518 and no leak any more.

BTW how is the shifting with that oil in there? It seems to be branded as diff oil rather than gear oil so presumably has a large amount of friction modifier in there which is not what synchros want. But then again if it works.....

 

I epoxy painted the inside of my pans to stop the leaks in the castings. They are amazingly porous from the factory.

 

I was told if it doesn't leak its probably out of oil..

 

I think you have answered your own question there.

Nothing about the "oil" you put in there is correct for this application ---

1) It is the wrong viscosity
2) It is for LSD rear ends (not manual gearboxes), so it probably has "friction modifiers" blended in it, which are not appropriate for the gears and synchros of that ZF box ---- and it may also contain additives which may be corrosive to certain alloys (e.g., brasses).

I would recommend that you drain it, refill with the proper gearbox oil, and see if the leaks persist.

Regardless, that LSD product should not be in there, anyway ---- it is likely to cause other problems after extended use.

 

This stuff...
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I've use that stuff before on my Lancia's and they work very well.