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Discussion Starter #1
Ive read a lot of the posts regarding which oil to use in the 5 spd gearbox of my car (which may or may not have the brass synchros). I found the discussions a bit confusing but Ive decided to use this:

Redline MT 90 : no reactive sulfur additives : good for brass synchros......recommended for GL1/3/4 applications....


Any thoughts ??

thanks
roger
 

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But Mad North-Northwest
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10,743 Posts
Brass & yellow metals aren't an issue in Alfa gearboxes.

If you've got the original steel synchros you want to use plain GL1 (like the stuff Napa sells.) I've personally tried the MT90 in my '63 because it calmed to meet GL1 and found it did not work very well with the synchronizers.

If your transmission has been upgraded to moly synchros you can use the stuff for the later cars. A lot of folks around here like Redline 75W90NS.
 

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Discussion Starter #3
thanks Gubi!

For Napa GL1, its this:
Correct?

It doesn't have the upgrade to moly synchros so that rules out the Redline 75W90NS.

Could you clarify "Brass & yellow metals aren't an issue in Alfa gearboxes", because I thought that early versions of the grearbox did have Yellow metal....no? They didnt have brass synchros ??

Thank you for your help
Roger
 

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But Mad North-Northwest
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That Napa stuff is correct, yes.

None of the '60s Alfa gearboxes had brass synchros. The early boxes had plain steel synchros, and EP lubricants do not work well with those: it's not a corrosion issue, it's a friction issue. The later boxes (can't remember the switchover point...1970 maybe?) had moly synchros and spec'd EP.

The MT90 uses ZDDP as an EP additive (instead of the more typical & corrossive sulfur compounds) but it's still EP. I tested it out in the '63 but it wasn't a good choice.
 

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Shell Dentax is the right stuff!
 

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But Mad North-Northwest
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Shell Dentax is 90wt GL1, which is the spec for gear oil without friction modifiers or EP additives. The Napa product is equivalent.

Dentax works fine if you can find it, but I'm not even sure it's still being manufactured by Shell.
 
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