Best weight of trans oil - 75W90 or 75W140 ??

[Martin S.]

It does look like chunks, but I think it is metal particles formed like that with the magnet. I wiped and blew it clean and didn't see any chunks, thank goodness! But there were lots of shiny particles suspended in the oil. 

[Andrew]

It does look like chunks, but I think it is metal particles formed like that with the magnet. I wiped and blew it clean and didn't see any chunks, thank goodness! But there were lots of shiny particles suspended in the oil.  

Phew, as you say , thanks goodness for that!

I have heard Swepco oil being recommended, but it ain't cheap.

[Martin S.]

I don't have a problem buying pricey oil, but I'd like to be sure about which weight of oil is the best. So far I haven't noticed a difference with the 75W140 but the weather has been cool. I suspect that when it's hot out and after driving fast on the highway, that's when the 140 will kick in and not thin out as much which would be nice. Also if the oil gets that contaminated after one summer of driving, then it's a good idea to change it, at least in the first year or two.

[Martin S.]

I’ve been changing gear oil every season for the fun of it, and trying new oils to see how they compare. When my supplier recommended Redline Oils, I remembered them from motorcycling and thought I’d give them a try.
I emailed their tech help asking about which oil to use in my VW and this is what Dave Granquist told me:

“The 75W140 wouldn’t be recommended in a synchro equipped transaxle as it could be too slippery for the synchros.
Typically in a VW transaxle the MT-90 would be recommended, though if you preferred a higher viscosity the 75W140NS would be suitable.”

I had no idea that gear oils had different amounts of slipperyness (and is that even a word lol)

But he was right! I noticed instantly easier shifting in my Rancho using the MT-90.
I also did not know 90 weight gear oil was available in synthetic, at least from Redline who only sell synthetic.
Another lesson learned.

[jim martin]

here you go thought I would toss this option out there - i have used allot of oil products in the past .but after trying this for the past 3 years , im SOLD no need to try anything else .
 no wear issues found during last 2 inspections /4th gear ratio changes .
launches are very hard and shifting is quite fast but very smooth .
gearbox is full synchro


https://torcoracefuel.net/products/torco-rtf-racing-transmission-fluid

https://cdn.shopify.com/s/files/1/0058/8110/2447/files/RTF.pdf