What Fluid Goes In The Gearbox

Oh Nooo !!!:

The great oil debate starts again!

I too have an overdrive (A-type) in a TR6. I too was perplexed about the situation. Thinking that 90 was great I went to the local very experienced and ancient TR guy for advice. Chris Hollum (Montreal's Mini maniac, but great in all other marques too, showed me the fax he had received from Laycock de Normanville wherein they swore up and down that one should never use 90 weight as it would cause the components of the unit to work slowly and wear rapidly. He hasd so disbelieved them that he called the firm and talked for an hour trying to verify this story. They recommended racing 20W50 motor oil for a transmission containing one of their overdrives. Thus that is what I use (Valvoline Racing 20W50). I am in a high state of nerves waiting to see if all will work out, but it's been a year so I guess we are surviving...

Mark Hooper

For context, the Bentley Book suggests the following fluids for the gearbox, overdrive and lower steering swivels on page 57 of my edition. These are the U.S. companies that I know still exist (although their product may not). I make no claims of knowledge for overseas (er, Home Market) corporations.

Component	Air Temp	API #	BP	Castrol	Mobil	Shell	Texaco
Gearbox etc	Over 0C/30F	GL4	BP Gear Oil SAE 90 EP	Castrol Hypoy	Mobilube HD 90	Shell Spirax(sic?) 90 EP	Multigear Lubricant EP 90
Gearbox etc	Below 0C/30F	GL4	BP Gear Oil SAE 80 EP	Castrol Hypoy 80	Mobilube HD 80	Shell Spirax(sic?) 80 EP	Multigear Lubricant EP 80

-J.B. Zimmerman
...from The Complete Official Triumph TR6 & TR250 1967-1976, Robert Bentley, pub.