you could try this link http://www.gtd40club.co.uk/magazines.php?date=2005-04-01
gtd club magazine spring and summer 2005,Genesis Of GTD Part 1 & Part 2
Brian
21 gearbox oil leak
Ian.
the hole is for the speedo senser,which was fitted to the renault 25 box
the 21 has a cable drive and has a much larger hole,best bet is to purchase
a senser to plug the hole
best of luck Brian.
Ian I believe Renault used this as a anti theft devise that locked the gear box in reverse gear,it just needs a metal threeded blanking plug with washer to seal it off
Brian I used the same on my GTD works great,make sure you dont glue the board upto the edge of the door,as the return edge of the sill fits between the board and the top panal edge covering the tanks,best of luck with you build Brian
Simon,
the 21 has a 3.44 diff,the 30 has a 3.89 diff,which gives the 21 a higher gear ratio.
externally i believe the only difference is the 21 has a cable speedometer drive,and on some of the 30 they had a magnetic sensor,
Brian