Quote from: 6s1640 on June 30, 2026, 09:59:10 PMHi all,
I am refilling the BW T10-M1 with new gear oil. The owner's manual says 3.5 pints and to use 90W, mild to extreme pressure-M568-D. When filling, I was only able to get 3 pints in. So just for grins, I check with the internet on best way to fill and what I learned was to only use GL-4 80W-90 gear oil. It turns out I put in GL-5 80W-90. The info I am getting and confirmed with the NAPA guy, the GL-5 is corrosive on the brass synchro's and should not be used on our older transmissions. I have drained it out. Ugh. Now I am looking for the correct GL-4 80W-90 gear oil, but none of the retailers stock, so I am having to go mail order or special order.
Do you have a recommended brand, old school gear oil 90W? I want to stay away from synthetic and used regular gear oil, just like back in the day.
Thanks
Cory
Cory,
Redline makes some good products. I have a wide ratio toploader on my exSCCA 67 Mustang sedan racer use their gear oil in it, works well. You might give it a looksee.
Dave

