Grey colour 18 tooth (18.8mm diameter)to go with the 7 tooth Red colour coded larger worm drive spindle
TXF10004which is 23mm in diameter-for
SPI overseas 3-2 ratio diff.
BEWARE-there is also another smaller worm 7 tooth spindle
DAM6028 @21.37mm wide(21.1 WORN).
Beware also of red or blue colour plastic pinions from Metro boxes which were (21mm diameter)
SO NOTE-TXF10004 and
TXD10006 were a special sized pairing.
Used in 3.2 diff ratio SPI gearboxes which were different to metro equivalents which had 13" wheels but used.
See
AKM2 parts list page 45 for full chart
-All of the late type drive pinions were at least £36-00 new, jan 2000
you can use
DAM6028 7 tooth and
22G2024 red 18 tooth for this 3.2 ratio combination with 12"wheels.
Plastic worm gears used on production minis.
15 teeth
TXD10004 black worm special size
16 teeth
DAM2905 green worm
17 teeth
22A1881 clear/white worm
18 teeth
TXD10006 grey worm special size