Customs Trans fluid for ‘56 manual trans.

Looking for the correct GL and weight trans fluid for. ‘56 For 3-speed manual transmission.

 

Used to run 90 weight in them. My 57 Mercury shop manual lists SAE 80 Multi-Purpose.

 

Just about any 90 axle/trans is good, but I've been thinking about something I can't seem to shake. Good topic for it. Syncros are like "clutches" in a manner of speaking. I've been wondering if posi rear axle fluid would help syncros work better...? Maybe help stop the gears when the shift happens. I dunno my fellow HAMB folk, am I full of gear dust on that? Packard transmission manual refers to theirs as a syncro clutch. If I'm out in left field here I can take it.

 

Synchronizers are br*** cone clutches. Half way though your shift they are either speeding up or slowing down the gear you are selecting. If anything I would think posi fluid would tend to make them slip rather than grab.

 

This was supposedly another of the advantages of running ATF in a manual transmission.

 

GL4 by the way

 

Pennzoil Synchromesh, for old trans. Ok for br***, $10 at AutoZone

 

There is also a synchromesh with a GM part number on it. A mechanic buddy of mine swears by it over GL4. I looked it up and saw that AC Delco makes one.