I have a rather large leak out the engine side of my 1989 westi.   I believe it is the main seal .  Is there any way of working this except to take out the engine and tranny?     If that is it what should I get done while it is out.   the engine was bebuilt 25K miles ago and 4 years.   I have tried some Lucas Tranny additive, no diff.    I have heard of using brake fluid to try to plump up the seals, a little scared ot that as it is so corrosive.  
   Second issue is while the tranny is out should I find someone that could get a little taller gear in 4th.???   Also sinchro in 2nd grinds a little in the cooler weather when the oil is thicker, ok when it warms up..  Anyone have a rebuilt with higher gearing??  

Thanks for input
Tom Jansen 
Coppell, Texas....