I just use Castrol EP80 / GL4 gearbox oil as the Sierra would have been filled with. The change is slightly notchy when cold but great when warmed up.
MTL is 75w80
Mtl 75w80 thank you
Back driving a seven again after more than twenty five years
Now that we have settled on an answer should that go somewhere in the Guides? Maybe in Guides or a new FAQ on fluids incorporating a summary of Andrew's excellent work on VVC oil?
Same for the recent correct MOT emissions level discovery. Can that be captured somewhere along with the flowchart and table of values so it can be easily printed and taken to the test centre?
If someone did a quick search these, and the many other useful pieces of information, should show up first and preferably without having to read several pages of discussion to get to the answer.
Q Catcher: could you be persuaded to summarise all the contributions in one post, ready to be picked up as a Guide/ Wiki, please?
Well, on the strength of all the recommendations above, I've ordered 2 litres of Red Line MTL GL4 75w80. So my summary is:
For the Ford T9 gearbox, which we believe was probably filled with Castrol EP80 GL4 back in the day, when it was on a Ford Sierra, the collective wisdom is now that Red Line MTL GL4 75w80 is the best modern equivalent and provides the best shift quality. GL4 is the most important part of the spec, i.e. don't use GL5. And the gearbox takes 1.2 litres from empty.
Where is the best place to keep this where it can easily be found in the future? Guides, FAQ, a new section on recommended fluids or maintenance?
I'd suggest a Guide. (Especially as Guides are now ready to become multiauthor Wikis.)
Is the box out or newbuild? They dont usually have a drain plug.