[AC TC]

be careful with syn´s i these, they may get notchy due to syncronisers not working
good.
The dex use was probably just for keeping a lowe oilstash at the dealer, dex is not a perfect oil for manual trannys.
I would look for a dino 75w, 80w- 90 GL4 oil or one of the "syncro" mtf´s thats avail. i wouldn´t choose a light wheight
mtf ( "mtl" ) i i had a choice and i wouldt use "shockproof" from rli either ( its a racing oil, nothing for 100 kmiles)

 

[AC TC]

This is what i would use: Redline oils 75w90 NS Gear oil.
Dex is a lousy gear oil, if i would usea an atf it would be atf+4 but i have no
idea what the friction modifiers in it would do to the synchros. (atf+4 would probably meet the GL4 standard, dex- not a chance)

 

[AC TC]

AC TC I realize that oils of all kinds have improved/changed changed over the years but 75w90 is a lot thicker than dextron is it not?, how sure are you of it working without issues? have you tried it before yourself?, I am up to switching as I am going to have to drain this thing again anyway.

I´ve used it myself in a a833.
Its not all that much thicker than dex but it is a real gear oil.
Note that you shuold stay away from GL5 oils unless youre super sure that they
dont contain LS additive or soft metal eating EP additives. (rli clears both)
Going with a GL4 clears both. GL5 is great for rear axles wich have the "sliding" hypoid type of gears.