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Old 25 Sep 2012, 07:00 pm   #2 (permalink)
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Default Re: Differential fluid in 1998 Corolla

On 9/25/2012 1:39 PM, SuperBK wrote:
> 1998 Corolla with a 3 speed auto trans. I've established that its
> separate fluid for the transmission and the differential / transaxle.
> The differential is filled with a plug facing the firewall. Online I
> have found that the fluid is Dextron III auto trans fluid for the
> gearbox, but what drained out to me looks like gear oil - maybe 50
> weight. Anybody know for sure. Thanks Brian

Dunno.. I'd want to make sure.. And it does sort of sound
like it had gear oil instead of ATF.. ATF would be reddish,
and would have the usual ATF smell.
Gear oil will usually be yellow-brownish and have a totally different

What makes it confusing is the manual says that you use ATF in
both, but some people like you, claim that there was likely
gear oil in the differential.
Myself.. I think it likely was gear oil.. Back then, most were
separate, and many differentials did use gear oil I'm pretty sure.
But 50 weight seems to be hard to come by, and most is the usual
70-90 or whatever weight.. So you then worry if that might be
too thick when it's cold..
It is a dilemma that's hard to get a straight answer to..
But if the old stuff was gear oil, I'd be able to tell from the
smell. It doesn't smell anything like ATF.

On my 4 speed, they are connected, and the whole mess runs on
ATF.. So I guess ATF is capable of keeping it lubed..
But I bet gear oil is a bit better as far as gear wear, etc..
I think one reason they are now using ATF for the whole thing
is for better gas mileage. ATF is thin, even in cold weather..
That's also why mine uses the light 5w-30 oil.. And the newer
ones seem to be going to even lighter oil.
I wish I could find some 50 weight gear oil as I need to change
the oil in my old Ford truck, and it prefers 50 weight gear
oil. But.. it seems hard to find these days.. I might try the
dealer.. They used to stock it I think.. Mine has the old T-18
four speed.. It will on 90 weight, but it's really too thick
for winter.. It likes 50 better.

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