TR2/3/3A Proper oil TR3 Transmission

I have not changed the oil since my transmission was rebuilt around 1985. The manual calls for 50 weight oil. In the past I had used 30 weight in it as well as an MGA. I know some owners who had used the 75w90 standard transmission oil. Your
current thoughts are appreciated.

Aloha Kenny,

I found a preety good discussion of motor oil versus gear oil on the Vintage Triumph Registry website.

https://www.vtr.org/maintain/lubricants-redline.html#atf

There is alot of information regarding what you might use in various parts of the car, including greases and brake fluids. A big difference in comparing gear oil and motor oil is that the viscosity of gear oil is taken at 150 deg F, and motor oil is measured at 210 deg F. I think the owner's manual for the TR3 calls for gearbox oil to be 30 weight motor oil. This is probably the same viscosity as an 80 weight gear oil. I am currently using Mobil 1, 5W50 motor oil in my TR3 gearbox.

Safety Fast,
Dave

The factory originally called for 80 /90 wt for the non OD box, this is good for most driving. I have also had fine service from STP (1/2 can) added to the gear oil for quieting bearing whine
in a well worn box. If you have an OD box there are lots of opinions on what to put in, as the different manufactures recomended different oil for the same Laycock OD!! I vote for the 80/90 straight up and changed every year to add life to the dear old Laycock.
MD(mad dog)

OK it looks like motor oil is the proper thing with the brass parts etc so how many quarts do I need? I am thinking 30 weight Non-detergent.