I changed that seal ones when I rebuilt my gearbox.
Driven 20.000 km since and no leaks yet ...
Just make sure you get the correct "O" ring.
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<font color="blue"><i>1981 TR7 FHC Sprint (better known as 't Kreng)
1981 TR7 DHC (not very well known yet, but back on the road)
Also a 1980 TR7 DHC, 1980 TR7 DHC FI, 1981 TR7 FHC
http://tr7beans.blogspot.com/</i></font id="blue"></center>