Transmission and tcase fluid?

[rangeron33s]

Alright so I just got back from a 20 sit in at orielly while they were trying to look up what weight of fluid touse in the transmission and tcase on my 88 ranger. They said mercon in the tcase. Is that correct? And then they had to call up somewhere to get the info for my 88 fm146 and they said I have to use 75w90 synthetic gear oil in it. I'm very confused. Please help me out here
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[FritzTKatt]

Tech section says 80-90 in that. 75-90 wouldn't hurt for winter use I suppose. Tech section lists Dextron in the 1350, but other sources say mercon, as I though. IIRC my haynes manual listed mercon. Either way they are ATF and wouldn't be as bad as using gear oil in it. I'd go with mercon because it is a ford...

 

[exbass94]

Tech section says 80-90 in that. 75-90 wouldn't hurt for winter use I suppose. Tech section lists Dextron in the 1350, but other sources say mercon, as I though. IIRC my haynes manual listed mercon. Either way they are ATF and wouldn't be as bad as using gear oil in it. I'd go with mercon because it is a ford...

Dexron III is the exact same thing as Mercon. The only difference is Dexron is a registered trademark of GM and Mercon is a registered trademark of Ford. They literally have different names for the same thing. Look at any bottle of Dexron III and it'll say "Dexron III/Mercon" or "Dex/Merc" for short. (I should note though that there are several different kinds of Dexron and Mercon fluids, and they're not necessarily all the same. It just happens to be that Dexron III is the same as regular Mercon.)

And yes, that's the correct fluid for the transfer case.

You don't have to use synthetic in the transmission. You could, but you don't have to. Use any 90 weight gear oil (80w-90, 75w-90) and it'll work fine.