Which is Best Manual Transmission Fluid ?

[DOCTORBILL]

Reading around about Geo Metro manual Transmission fluid, I get
the feeling that this is a controversial topic.

It looks like it is a toss-up between GM Sychromesh and Redline MT-90.

Any fervent opinions from the early 90's Geo Metro owners ?

Mine is a '93 with 3 cyl 5 speed manual.

It shifts nicely, downshifts nicely and I am wondering if I should
change the fluid as I bought it used and GOD ONLY KNOWS if or
when the fluid was changed.

Maybe 'If it ain't broke, don't fix it' applies here since some folks
seem to aquire transmission problems after changing their fluid....

DoctorBill

[t-max]

I'd change the fluid. As for what brand, well, I will admit that I use a generic brand from Canadian Tire. Perhaps someone will chime in with the benefits of a particular brand.

cheers,

Originally Posted by DOCTORBILL

It shifts nicely, downshifts nicely and I am wondering if I should
change the fluid as I bought it used and GOD ONLY KNOWS if or
when the fluid was changed.

Maybe 'If it ain't broke, don't fix it' applies here since some folks
seem to aquire transmission problems after changing their fluid....

DoctorBill

[DieInterim]

Originally Posted by DOCTORBILL

Reading around about Geo Metro manual Transmission fluid, I get
the feeling that this is a controversial topic.

It looks like it is a toss-up between GM Sychromesh and Redline MT-90.

Any fervent opinions from the early 90's Geo Metro owners ?

Mine is a '93 with 3 cyl 5 speed manual.

It shifts nicely, downshifts nicely and I am wondering if I should
change the fluid as I bought it used and GOD ONLY KNOWS if or
when the fluid was changed.

Maybe 'If it ain't broke, don't fix it' applies here since some folks
seem to aquire transmission problems after changing their fluid....

DoctorBill

Use what the manual recommends.
Now here is the part where I ruffle the feathers of REDLINE fanatics...
dont do it! Lets think this through logically.

First off most users who are having shifting issues - clunking, slow engagement, grinding - already have problems with their synchros. They report and improvement.

If you live in a cold climate and find shifting issues when cold. They report an improvement.

Well the one with cold shifting issues could go to a lighter gear oil in the winter. The others with already fuddy sychros...well they are just buying time with redline.

Synchros work by friction, so essentially one could say they are a cone brake. When you shift the synchro is pushed against the gear whick quickly spins it to synchronized speed and then the shift collar engages the gear. When the syncros wear or have been treated with teflon additive, they lose the ability to quickly spin the gear up to speed before the collar tries to engage the gear. Mismatched speeds = grind.

So how does Redline "Improve" worn/contaminated synchro cones? It does it by increasing friction. In other words its a light oil and the parts rub against each other more instead of a thick oil film that seperates them like standard gear oil offers.

So in short.. sure it will improve shifting, but expect to replace synchros in the near future due to the increased wear. Dont take my word for it, I can point you to many people that swear REDLINE hosed their transmissions. (I disagree, I think that their transmissions were needing service anyway.)

For me, I use clean, fresh, standard gear oil. Heavier in warmer climates, lighter in colder. (Mine is stubborn when its cold; I drive one block in 1st gear and its all ready to go.)

FWIW,
Blake

[mik13usa]

standard gear oil in these transmissions is just a bad idea. Period.! The manual may say use GL 4 BUT... The cars originally came with GM synthetic Synchromesh. How do I know? I worked at one of those oil change places for years, many years ago. Any time someone would change the oil to the Manual reccommended they would begin to have problems. It is just like Blake said, the GL is to slick, it does not allow for the proper friction element to engage the gears properly. Again this is only my opinion. And any one who swears that Redline hosed their tranny, I would love to see them personally. I have done years of research about the subject, and have yet to see the transmission ever built NOT perform better with a synthetic Esther based gear lubricant.

[DOCTORBILL]

Originally Posted by DieInterim

Use what the manual recommends.
.
.
.
For me, I use clean, fresh, standard gear oil. Heavier in warmer climates, lighter in colder. (Mine is stubborn when its cold; I drive one block in 1st gear and its all ready to go.)

FWIW,
Blake

OK.....what you say makes sense.

The Chilton Manual says, "When adding fluid or refilling the manual
transaxle always use GL-5, 80W or 80W-90 weight gear oil."

Any brand better than another?

Is GM Syncromesh gear oil a specifically better oil?

My transmission works well, even at 7 °F after a while.
Makes whining noises when really cold until it warms up.
I just start the engine with the clutch in, hold the clutch
in until the engine warms a bit (60 seconds) and slowly
let the clutch out. Nearly kills the idle, but eventually
it warms the transmission enough to not be noticable.

In the summer - works fine.

I just want to MAKE SURE the gear oil is OK. Bought the
car used at 145,000 and don't KNOW if the trans oil was
ever changed. Ever!

Manual Transmission lube shouldn't degrade tho, should it?

Only thing is, if never changed EVER, may have some metal
chips in it from the Factory....


Again - best brand? Other opinions?

DoctorBill

[DOCTORBILL]

Originally Posted by mik13usa

standard gear oil in these transmissions is just a bad idea. Period.! The manual may say use GL 4 BUT... The cars originally came with GM synthetic Synchromesh. How do I know? I worked at one of those oil change places for years, many years ago. Any time someone would change the oil to the Manual reccommended they would begin to have problems. It is just like Blake said, the GL is to slick, it does not allow for the proper friction element to engage the gears properly. Again this is only my opinion. And any one who swears that Redline hosed their tranny, I would love to see them personally. I have done years of research about the subject, and have yet to see the transmission ever built NOT perform better with a synthetic Esther based gear lubricant.

Now I am confused.....

So - are YOU saying Redline is OK ? Blake says not...
Are Redline and GM Syncromesh "synthetic" lubricants?
Are they equivalent to each other?

Are they not OIL products? What do you mean "STANDARD" ?

If these Geos originally came with "GM synthetic Synchromesh" in the
manual transmission, perhaps I had best stick to THAT !

I am a retired chemist and know what "Oil" is but not what these
so called 'synthetics' are made of. You said Esters.
Is there a web site that explains the chemical composition of these
goodies?

Transmissions amaze me. I never could understand EXACTLY how
they do what they do - the syncromesh part that is.

And Automatics are an enigma wrapped in a mystery....

Fluid hydaulics! Hummmm....

So, again - which is best...?

What means GL anyway?

If I open my transmission and obtain a small sample of what
it contains NOW, how can I tell if it is Synthetic or OIL based?

DoctorBill

[DieInterim]

Originally Posted by DOCTORBILL

OK.....what you say makes sense.

The Chilton Manual says, "When adding fluid or refilling the manual
transaxle always use GL-5, 80W or 80W-90 weight gear oil."

Any brand better than another?

Is GM Syncromesh gear oil a specifically better oil?

My transmission works well, even at 7 °F after a while.
Makes whining noises when really cold until it warms up.
I just start the engine with the clutch in, hold the clutch
in until the engine warms a bit (60 seconds) and slowly
let the clutch out. Nearly kills the idle, but eventually
it warms the transmission enough to not be noticable.

In the summer - works fine.

I just want to MAKE SURE the gear oil is OK. Bought the
car used at 145,000 and don't KNOW if the trans oil was
ever changed. Ever!

Manual Transmission lube shouldn't degrade tho, should it?

Only thing is, if never changed EVER, may have some metal
chips in it from the Factory....


Again - best brand? Other opinions?

DoctorBill

Old oil can contain moisture, oxides, and acids that chew at the netal. Even though it may have high lubricity, it can be chewing away on your parts.

Blake

[DieInterim]

Originally Posted by DOCTORBILL

Now I am confused.....

So - are YOU saying Redline is OK ? Blake says not...
Are Redline and GM Syncromesh "synthetic" lubricants?
Are they equivalent to each other?

Are they not OIL products? What do you mean "STANDARD" ?

If these Geos originally came with "GM synthetic Synchromesh" in the
manual transmission, perhaps I had best stick to THAT !

I am a retired chemist and know what "Oil" is but not what these
so called 'synthetics' are made of. You said Esters.
Is there a web site that explains the chemical composition of these
goodies?

Transmissions amaze me. I never could understand EXACTLY how
they do what they do - the syncromesh part that is.

And Automatics are an enigma wrapped in a mystery....

Fluid hydaulics! Hummmm....

So, again - which is best...?

What means GL anyway?

If I open my transmission and obtain a small sample of what
it contains NOW, how can I tell if it is Synthetic or OIL based?

DoctorBill

API - American Petroleum Institute

GL is Gear lube specification.
So API GL4 has difference properties than GL5.

Example: Some rear ends have copper washers inside them; these need GL4. If you were to add GL5 to this rear end and for some reason the oil reached 200 degrees F, the copper would "melt" away.

Mineral or Synthetics, it does not matter as long as the specifications are the same. Yes synthetics are nice, and very expensive.

You make the call.

Blake

[bhrollin]

The owners manual for my 1997 1.0 5 speed metro says to use castrol syntorq. The difference is that synthetics flow at lower temperatures and can take higher temps without breaking down.

[DOCTORBILL]

Whilst in Schuck's this morning buying a Bosch O2 Sensor, I bought
three quarts of Valvoline Durablend SAE 80W-90 Gear Oil.

$6.00 per quart. "Synthetic Blend" - API services GL-5, MT-1

Now - everyone tell me I made a Bad Choice.....

It is a synthetic, not all that expensive, and a 'name brand.'

Now if the weather here in Spokane will abate for a while, I will
endeavor to change my gear oil.

DoctorBill

PS - when I bought this '93 Metro, someone had put a turned metal
gearshift knob on the shift lever. 'Bout froze my hand to it when it
got down to 6 °F !!!

So I went to a crafts store and bought a 4 inch wood ball, waxed it,
drilled it out and hotmelt glued it to the shift lever.

Works Fantastic! Fits my hand nicely, isn't as cold as a
witch's boob on Halloween, and looks 'neat!' Tubular! Knarlie!
Hey, Man! Bitchin'! .....shows how old I am!

[DieInterim]

Originally Posted by DOCTORBILL

Whilst in Schuck's this morning buying a Bosch O2 Sensor, I bought
three quarts of Valvoline Durablend SAE 80W-90 Gear Oil.

$6.00 per quart. "Synthetic Blend" - API services GL-5, MT-1

Now - everyone tell me I made a Bad Choice.....

It is a synthetic, not all that expensive, and a 'name brand.'

Now if the weather here in Spokane will abate for a while, I will
endeavor to change my gear oil.

DoctorBill

PS - when I bought this '93 Metro, someone had put a turned metal
gearshift knob on the shift lever. 'Bout froze my hand to it when it
got down to 6 °F !!!

So I went to a crafts store and bought a 4 inch wood ball, waxed it,
drilled it out and hotmelt glued it to the shift lever.

Works Fantastic! Fits my hand nicely, isn't as cold as a
witch's boob on Halloween, and looks 'neat!' Tubular! Knarlie!
Hey, Man! Bitchin'! .....shows how old I am!

Good choice. I laugh at the speed racers who buy the speed stuff and own an econo-box. Even worse add all of the wings and ground effects that actually create drag and reduce the terminal speed of the car. Blumentopft!

Fer shizzle my nizzle.
Blake

[DOCTORBILL]

Originally Posted by DieInterim

Good choice. Fer shizzle my nizzle.
Blake

OK....I thought I knew how to insert a picture in my "Signature" as
you have been doing - but I don't!

I've got the "Avatar" pic down OK, but I don't know how to include
a picture 'with' my signature file.....

Can you describe HOW you are doing that?

DoctorBill

[DieInterim]

Originally Posted by DOCTORBILL

OK....I thought I knew how to insert a picture in my "Signature" as
you have been doing - but I don't!

I've got the "Avatar" pic down OK, but I don't know how to include
a picture 'with' my signature file.....

Can you describe HOW you are doing that?

DoctorBill

Sure!

In the sig line use the [IMG] tags. The pictures I use are linked via the web.

EXAMPLE -

Cheers!
Blake

[archer973]

I've come along 10 years after all the other posts looking for an answer to the question, "Which lubricant do I use in my 1996 Geo Metro, 1.0 L, 3 cylinder, 5-speed manual transmission. It seems the prevalent answer here is go with what the manual says. I have a Geo owner's manual, a Chiltons and a Haynes. They all agree the correct lube is GL-5. But in searching the internet I found that this is controversial and I found a couple of documents that sound highly informative and technical and they recommend GL-4 due to the use of yellow metals in the synchros.

Well, I cannot be sure who is the best authority, but I have one more insight I would like to add and I will state up front that this may not be the best source of information, but it does give a twist to the discussion. I was ordering lubricant, Red Line MT-90 (GL-4), from Amazon.com and using their filter to see if my selection was right for my vehicle. What I discovered is, their filter recommends this product for the M42 and M58 transmissions but not the MV2.

Maybe that is why the proper lubricant is an issue for this car. My car has the M58 transmission so I've decided to go with the GL-4, but I base this on a collection of sources, not just the Amazon filter.

[Crvett69]

i have been running syncromesh is all my metro transmission with great results. also when they changed the name to chevrolet metro in 98 they changed the fluid recommendation to syncromesh and its the same transmission as the older ones