mystery of corolla differential runs dry

My father's 97 corolla with the 3 speed transmission recently develop a
whine. Drove it to my usual mechanic where he suggested to try change
both the oil in the tranny and the differential to see if it helps.
(this transaxle has a seperate differential drain plug). The tranny was
drained first and the fluid looked and smelled okay. Then he open up
the drain plug of the differential - I could not believe my eyes that
only a few drops drained out, it was almost dry !

My question to the group is : how can the differential run dry without
my father noticing any leak ? I am very sure there is no stain on my
father's drive way, where he park his car 99% of the time. Where would
have the oil gone ? I was thinking of the drive axle oil seal but my
mechanic said it looked okay.

Last time the car had the transmission and differential oil change was
about one year ago at the same shop. I am thinking if my mechanic
forgot to fill the differential during the last change, how could the
unit went one year a few thousand miles without blowing up ? Actually
according to my dad the whine only developed in the last few days.

Any suggestion about what could have caused the leak ?

"Jack" > wrote in message
oups.com...
> My father's 97 corolla with the 3 speed transmission recently develop a
> whine. Drove it to my usual mechanic where he suggested to try change
> both the oil in the tranny and the differential to see if it helps.
> (this transaxle has a seperate differential drain plug). The tranny was
> drained first and the fluid looked and smelled okay. Then he open up
> the drain plug of the differential - I could not believe my eyes that
> only a few drops drained out, it was almost dry !
>
> My question to the group is : how can the differential run dry without
> my father noticing any leak ? I am very sure there is no stain on my
> father's drive way, where he park his car 99% of the time. Where would
> have the oil gone ? I was thinking of the drive axle oil seal but my
> mechanic said it looked okay.
>
> Last time the car had the transmission and differential oil change was
> about one year ago at the same shop. I am thinking if my mechanic
> forgot to fill the differential during the last change, how could the
> unit went one year a few thousand miles without blowing up ? Actually
> according to my dad the whine only developed in the last few days.
>
> Any suggestion about what could have caused the leak ?
>
What was the oil level in the transmission?
--
Ray O
correct the return address punctuation to reply

On Thu, 01 Sep 2005 18:28:25 -0700, Jack wrote:

> My father's 97 corolla with the 3 speed transmission recently develop a
> whine. Drove it to my usual mechanic where he suggested to try change
> both the oil in the tranny and the differential to see if it helps.
> (this transaxle has a seperate differential drain plug). The tranny was
> drained first and the fluid looked and smelled okay. Then he open up
> the drain plug of the differential - I could not believe my eyes that
> only a few drops drained out, it was almost dry !
>
> My question to the group is : how can the differential run dry without
> my father noticing any leak ? I am very sure there is no stain on my
> father's drive way, where he park his car 99% of the time. Where would
> have the oil gone ? I was thinking of the drive axle oil seal but my
> mechanic said it looked okay.
>
> Last time the car had the transmission and differential oil change was
> about one year ago at the same shop. I am thinking if my mechanic
> forgot to fill the differential during the last change, how could the
> unit went one year a few thousand miles without blowing up ? Actually
> according to my dad the whine only developed in the last few days.
>
> Any suggestion about what could have caused the leak ?


As far as the differential; most diffs are equipped with a vent, something
that looks like the top of a pressure cooker, that opens when the pressure
in the differential builds. These are known to rust and get stuck in the
closed position. When this happens, the pressure in the diff can't vent,
and pressure keeps building. So, what happens is that it starrs pushing
the oile past the seals, but usually only when the car is moving. The
pressure eventually drops and there may or may not be a leak shown on the
driveway.

"Jack" > wrote in message
oups.com...
> My father's 97 corolla with the 3 speed transmission recently develop a
> whine. Drove it to my usual mechanic where he suggested to try change
> both the oil in the tranny and the differential to see if it helps.
> (this transaxle has a seperate differential drain plug). The tranny was
> drained first and the fluid looked and smelled okay. Then he open up
> the drain plug of the differential - I could not believe my eyes that
> only a few drops drained out, it was almost dry !
>
> My question to the group is : how can the differential run dry without
> my father noticing any leak ? I am very sure there is no stain on my
> father's drive way, where he park his car 99% of the time. Where would
> have the oil gone ? I was thinking of the drive axle oil seal but my
> mechanic said it looked okay.
>
> Last time the car had the transmission and differential oil change was
> about one year ago at the same shop. I am thinking if my mechanic
> forgot to fill the differential during the last change, how could the
> unit went one year a few thousand miles without blowing up ? Actually
> according to my dad the whine only developed in the last few days.
>

I think your right on and they forgot to refill the differential. As to how
could it go for a few thousand miles without blowing up, that is easy.
All oil does in the differential is to keep the metal surfaces from rubbing
directly against each other and wearing. Once it is gone the metal
surfaces simply get polished as they rub against each other, and start to
wear out. The unfortunate part is that the gears in the differential right
now are probably just about completely worn out.

It's no different than a kids bicycle chain that gets wet and never gets
lubed.

If gearing immediately blew up when it ran dry, then lots of people
would have axles blowing up in their cars as they drive around, because
CV joint boots inevitably crack and fling all the lube out. What usually
happens though is it keeps working for a long time, then eventually when
it's very worn, it starts making a racket. Just exactly what happened
to your dad.

Ted

put the oem oil back in and drive it also
it sounds like your tring to get the shop to replace your diff for
free?

and if it blows well you know where the wine came from also find
another shop and check your tranny

The oil level was normal in the tranny.

I never knew of the vent that you mentioned. And this make me think of
another possibility. Recently there had been a small scale flooding
where my father lives. He told me he once drove through water as high
as the top of the bumper. Would it be that some water got past the vent
and enter the differential, push out some oil to the transmission ( I
think the tranny and the differential has a pathway where oil can
exchange). When the unit get hot the water got evaporate through the
vent, leaving very little oil in the differential.

Is this possible ?

well I am not trying to blame my mechanic, cause he is an honest guy
that I trust. But since he is also human, he is still prone to making
mistakes once in a while ..... my question is, my father's car runs
normal after refilling the differential, should I ask for some sort of
compensation from the mechanic ?

I don't think a mechanic would 'forget' to fill the differential - at
least on my 92 Geo Prism it required a lot of work, including moving
some kind of rubber thing, to get at the plug. What is more likely is
that this is the first time the thing has ever been checked. When I
checked mine it was low (not necessarily dry); I filled it up and put
everything back. It made little or no difference in operation of the
car. So I don't think you have a problem but anything could happen!

THere is the same rubber thing to be removed from my father's '97, not
sure what that part is for but it is there. I tend to believe my
mechanic since he has been a very competent and knowledgable guy ever
since I started using him six years back, but still everyone can make
mistakes.... if it is not him it would be difficult to find a reason
for this mysterious oil loss..


wrote:
> I don't think a mechanic would 'forget' to fill the differential - at
> least on my 92 Geo Prism it required a lot of work, including moving
> some kind of rubber thing, to get at the plug. What is more likely is
> that this is the first time the thing has ever been checked. When I
> checked mine it was low (not necessarily dry); I filled it up and put
> everything back. It made little or no difference in operation of the
> car. So I don't think you have a problem but anything could happen!