Effect of gear oil viscosity on transmission efficiency (Metroid owners take note)

[bzipitidoo]

The manual tranny in my Cortina is worn. It was becoming very difficult to shift into 2nd gear when starting out, needing a lot of force on the gearshift, even when not particularly cold outside. We changed the 80w90 it had for ATF. Couldn't say how much that helped FE, but that made 2nd gear much easier to shift into. The tranny has been working fine with ATF for a few years now.

[trebuchet03]

Great experiment

I know of at least one person over on mazda626.net that uses ATF in his gearbox.... He is in a cold region though

Not sure what I'm going to do for gear oil in my Jetta just yet... I might just bite the bullet and get the factory stuff... I haven't heard of any problems with it, other than the high price -- ~$20 per 500mL bottle and there's 2.1L in the gearbox!

[ZugyNA]

For trans that use ATF might try Mobil 1 synth ATF with Lubegard ATF additive.

Synth ATF is probably less viscous in cold temps...the additive reduces drag when hot.

For trans that use gear oil...use a moly additive?

http://www.molyslip.com/Testimonials...arms_Jan94.pdf

Look for the best moly prices...some is way expensive. Other additives like Militec also work.

[GasSavers_Ryland]

Every honda I looked at with a manual said to use 10W 30 in it, or the honda labled manual trasmition fluid, right now I have the 5W 30 Amsoil MTF that is labled as working for hondas, I think the same stuff is in my moms Metro tranny, and seems to be working great.
last summer I ended up switching back to 10W 30 in my tranny, because at around 228,000 miles the main bearing went out on it, and the thicker oil quited it down long enough for me to drive 1,000 miles home, thicker fluid does provide more cushin, so I wouldn't switch something that calls for 75w 90 over to 0w 20

[DracoFelis]

Originally Posted by Ryland

Every honda I looked at with a manual said to use 10W 30 in it, or the honda labled manual trasmition fluid, right now I have the 5W 30 Amsoil MTF that is labled as working for hondas, I think the same stuff is in my moms Metro tranny, and seems to be working great.

Yep, my CRX is also speced the same way!

In my case, after doing my research online, I went with the (synthetic) Red Line MTL 70w80 (my research suggested that Red Line made the best product for manual transmissions, whereas Amsoil had a better product for automatic transmissions). The Red Line MTL is actually thinner than the motor oil it replaces (and also rated specifically as a fluid that should save some gas), but still seems to do a good job at keeping everything lubed up (and cooled down) in the transmission. And honestly, it's amazing how smoothly (and easily) that car shifts now (with that Red Line fluid in its transmission)!

NOTE: The 70w80 rating is the "gear oil" rating, which doesn't have the same number scale as the motor oil rating. In fact that 70w80 is actually a little thinner than the 10w30 motor oil my transmission is rated for. Furthermore, the Red Line product is actually rated as being a good "direct replacement" for the fluid in any manual transmission (for example, my CRX) that was originally speced for 10w30 motor oil...

FWIW:
I did use the Amsoil's fully synthetic AFT for my wife's (auto-transmission) Civic, as well as our (diesel) Ford pickup's transmission. And both transmissions seemed to very much like the Amsoil "universal" synthetic ATF fluid.

BTW:
I'm now an Amsoil dealer, in case anyone (who isn't a current Amsoil customer of another dealer) is interested in any of their products. So if any of you want to try their products (and I do think some of their products, such as good synthetic oils and transmission fluids, can help some with FE), I'd be happy to offer gassaver members discounts. Just PM me if you are interested.

NOTE:
Amsoil dealer rules prevent me from selling to (or even offering discounts to) existing Amsoil customers (of a different dealer). So much as I would love to extend that offer of gassaver specials to all gassaver members, I really am only allowed to extend that offer to gassaver members that aren't current/existing Amsoil customers...

[BrianR7]

I remember reading in a tech manual that not all Geo Metros use the same transmission fluid in their manual transmissions. The book recommended checking the fluid you remove from the transmission to know which one to use. I also remember something about some Geo Metros being produced in Canada and some being produced in Japan. Perhaps one could tell which fluid to use based on where it was produced. I remember a salesman telling me that new Metros sold on the East side of the Mississippi river (in the U.S.) where made in Canada and the ones sold on the west side where made in Japan. I don't know how true this is. My first and Second Metros (92 Xfi, 94 base) where first sold on the east side of the Mississippi and where made in Canada. I remember being surprised at how thin the fluid was in both transmissions.

[MetroMPG]

Thanks for the extra info - that's interesting about the manual recommendation - pretty much what I did for my car.

The EV owner who gathered the info I posted at the top of this thread is driving a first gen Suzukiclone, so I'm sure his was made in Japan. Mine was built in Ontario.

[vt420]

redline MTL is a suitable replacement for syncromesh, in my experience.
regular gear oils dont have the friction modifiers to improve the syncro action like one of the specialty manual tranny fluids
penzoil actually makes gm syncrmesh and it's cheaper in the yellow bottle from a regular parts store

also note than on many manual transmissions GL4 gear oil is specified, if a GL4 is spec'd DO NOT put a GL5 gearlube in place of it. GL5 does not fully supercede GL4 in all applications as it contains additives that may be corossive to yellow metals (such the the bronze parts in many syncronizer assemblies)

as far as engine oil in a trans.. minis used shared oil, and saab at least used to spec 5w30 engine oil in their manual trannies. With a note saying do NOT under any circumstances use a synthetic motor oil.

My nissan will be getting redline MT90 (the heavy weight version of MTL) in the near future as it calls for a 75w90

Jeff

[green swift]

Originally Posted by DracoFelis

Yep, my CRX is also speced the same way!

In my case, after doing my research online, I went with the (synthetic) Red Line MTL 70w80 (my research suggested that Red Line made the best product for manual transmissions, whereas Amsoil had a better product for automatic transmissions). The Red Line MTL is actually thinner than the motor oil it replaces (and also rated specifically as a fluid that should save some gas), but still seems to do a good job at keeping everything lubed up (and cooled down) in the transmission. And honestly, it's amazing how smoothly (and easily) that car shifts now (with that Red Line fluid in its transmission)!

NOTE: The 70w80 rating is the "gear oil" rating, which doesn't have the same number scale as the motor oil rating. In fact that 70w80 is actually a little thinner than the 10w30 motor oil my transmission is rated for. Furthermore, the Red Line product is actually rated as being a good "direct replacement" for the fluid in any manual transmission (for example, my CRX) that was originally speced for 10w30 motor oil...

FWIW:
I did use the Amsoil's fully synthetic AFT for my wife's (auto-transmission) Civic, as well as our (diesel) Ford pickup's transmission. And both transmissions seemed to very much like the Amsoil "universal" synthetic ATF fluid.

BTW:
I'm now an Amsoil dealer, in case anyone (who isn't a current Amsoil customer of another dealer) is interested in any of their products. So if any of you want to try their products (and I do think some of their products, such as good synthetic oils and transmission fluids, can help some with FE), I'd be happy to offer gassaver members discounts. Just PM me if you are interested.

NOTE:
Amsoil dealer rules prevent me from selling to (or even offering discounts to) existing Amsoil customers (of a different dealer). So much as I would love to extend that offer of gassaver specials to all gassaver members, I really am only allowed to extend that offer to gassaver members that aren't current/existing Amsoil customers...

I run 70w80 in my swift and think it is the best oil I have run to date...
Shifting is smooth , cold weather operation is outstanding what can I say
No.1 oil in my books...

[DrivenByNothing]

Being in the process of rebuilding the transmission in the Jeep, I've done some research on this topic recently.

Contrary to popular belief, gear oil is not rated on the same scale as motor oil. "75 weight gear oil is actually about the same viscosity as 10 weight motor oil." ( http://www.calsci.com/motorcycleinfo/Oils1.html ). The reason motor oil is not normally used is due to the detergents and other chemicals that may be present in it. My Jeep transmission requires an oil that does not contain sulfur as it wears the 'yellow' metals quicker.

This leads me to an interesting fact. The Jeep owner's manual specifically calls for a GL-5 or equivalent gear oil. Most GL-5 oils contain sulfur. However, most GL-3 oils do not (possibly all of them). So misinformation from OEM can happen.

Yes, some transmissions (such as those in Saturns) call for ATF. The fact of the matter is that manual transmissions, although very similar in design, contain different tolerances and materials. As far as how thin the oil is when you drain it, had you just run the car? Transmissions don't get nearly as hot as engines, but they do heat up. As with most any liquid, viscosity changes with temperature.

From what I've read, for any transmission requiring gear oil (not ATF or possibly the honda trannies), Redline is one of the highest quality oils you can buy. It's just what Redline does and it's what they're good at. Personally, I will be using Penzoil Synchromesh in the Jeep trans.

The final verdict will probably come with time and a bit of trial and error, but I hope I cleared a few things up.

Matt