Changing the gearbox oil on a Triumph Stag

Why, and how often

Renew every few years or few thousand miles and top up if low. Match the oil to your transmission — a manual Stag, an overdrive Stag and a BorgWarner automatic all want different things.

Steps (manual)

1. 01. Warm the car and level it

   Warm the car with a short drive, then chock and raise it so it sits level.

2. 02. Filler plug first, then drain

   Find the filler/level plug FIRST (if it won't undo, don't drain). Then the drain plug; drain fully; clean it; refit with a sound washer.

3. 03. Fill to the level hole

   Fill through the level hole with the correct oil until it just weeps from the hole — that's the level. Refit the plug. Remember the overdrive shares the oil, so use the with-overdrive capacity as a guide if fitted.

4. 04. Automatic — dipstick, don't drain

   Don't drain unless you know the unit — check and top up via the dipstick with the correct ATF, engine warm and running.