What oil are you using in your manual transmission?

Andy J.

Andy J.

Doin’ it LIVE
Joined
Nov 5, 2005
Location
Winston
I pulled the plug to check the fluid level today and the stuff that came out looked like an old Dairy Queen blizzard :eek:. I´ve heard everything from straight gear oil to MT-90 synthetic. I´ve got a gallon of 75w90, will that work or should I run up to the parts store and get something else? It´s an 81 yota 5-sp. (L50?)
 
Castrol Syntorq. It's about elevendy brazillion dollars a quart, and hard to find. I would just use what the manufacturer recommends as far as weight and type. If they recommend synthetic, you should stick with synthetic, because non-synthetic can eat up certain types of synchros.
 
That 75w 90 will be fine for that old tranny. I've got mobile 1 75w 90 in my w56. Will switch to Amsoil if and when I ever change it.
 
I drained it and refilled it with 80W90. I will run it a little to let the oil heat up and change it again. The Haynes manual said ´gear oil´, so I guess I will go with that for now. BTW, getting those 3 qts in there was a PITA. I had some extra hose (beer line), so that helped, but damn.
 
Manual transmissions typically use GL-4 spec gear oil, so it more than just weight that you have to pay attention to. GL-5 is not recommended for manual trannys.
 
I think all the gear oils I saw at advance auto were GL5. They also have Pennzoil manual tranny fluid, but the bottle doesnt really give any specs. It just says good for GM and Chrysler manual trans.
 
Costal gear oil
 
This will tell you most everything you need to know:
http://en.wikipedia.org/wiki/Gear_oil
* API GL-1, oils for light conditions. They consist of base oils without additives. Sometimes they contain small amounts of antioxidizing additives, corrosion inhibitors, depresants and antifoam additives. API GL-1 oils are designed for spiral-bevel, worm gears and manual transmissions without synchronizers in trucks and farming machines.
* API GL-2, oils for moderate conditions. They contain antiwear additives and are designed for worm gears. Recommended for proper lubrication of tractor and farming machine transmissions.
* API GL-3, oils for moderate conditions. Contain up to 2.7% antiwear additives. Designed for lubricating bevel and other gears of truck transmissions. Not recommended for hypoid gears.
* API GL-4, oils for various conditions - light to heavy. They contain up to 4.0% effective antiscuffing additives. Designed for bevel and hypoid gears which have small displacement of axes, the gearboxes of trucks, and axle units. Recommended for non-synchronized gearboxes of US trucks, tractors and buses and for main and other gears of all vehicles. These oils are basic for synchronized gearboxes, especially in Europe.
* API GL-5, oils for severe conditions. They contain up to 6.5% effective antiscuffing additives. The general application of oils in this class are for hypoid gears having significant displacement of axes. They are recommended as universal oils to all other units of mechanical transmission (except gearboxes). Oils in this class, which have special approval of vehicle manufacturers, can be used in synchronized manual gearboxes only. API GL-5 oils can be used in limited slip differentials if they correspond to the requirements of specification MIL-L-2105D or ZF TE-ML-05. In this case the designation of class will be another, for example API GL-5+ or API GL-5 LS.
* API GL-6, oils for very heavy conditions (high speeds of sliding and significant shock loadings). They contain up to 10% high performance antiscuffing additives. They are designed for hypoid gears with significant displacement of axes. Class API GL-6 is not applied any more as it is considered that class API GL-5 well enough meets the most severe requirements.
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It has synchros. That's why you don't have to double clutch to shift.
 
That's what I thought, but everything I have read says use GL-4 and not GL-5 oil? Dang it, I think I'm just confusing myself :rolleyes:
 
Well, in the GL-4 section it says "These oils are basic for synchronized gearboxes, especially in Europe."
I believe brass synchros are not affected like the fiber synchros in more modern stuff.
 
GL4 is supposed to be "yellow" metal safe, hence the use with brass synchros. There is quite a bit of GL4/5 dual spec oil out there. Very little plain GL4 is available these days. Supposedly pure GL5 gear oil has additives that cause a problem with brass or "yellow" metal synchros.

FWTW, the Pinz specs GL5 for all gear boxes but GL4 for the tranny. I use a dual spec oil I bought at Tractor supply in a 5 gallon bucket for everything.
 
NC_Mog said:
GL4 is supposed to be "yellow" metal safe, hence the use with brass synchros. There is quite a bit of GL4/5 dual spec oil out there. Very little plain GL4 is available these days. Supposedly pure GL5 gear oil has additives that cause a problem with brass or "yellow" metal synchros.
FWTW, the Pinz specs GL5 for all gear boxes but GL4 for the tranny. I use a dual spec oil I bought at Tractor supply in a 5 gallon bucket for everything.
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Thanks for the info. I will keep a look out for that dual spec.
 
i got big container or GL4 from my local Napa store. I changed the fluid in my tranny and most of the info I got on the net said to use GL4. I do not know if GL5 would have negatively affected anything. 81 5 speed yota trans.
 
transman731 said:
i use gl-5 in anything that takes 90w oil. i have never had an issue with it hurting synchros. i have to warranty my work so if it would hurt them i wouldn't be using it.
the synchros it does hurt are the paper lined synchros.
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i will change my statement slightly, i run gl-5 in almost all manual trannies that call for 80w-90.

it also matters where you live, i've seen people in very cold places run atf in a manual trans and it work just fine.
 
transman731 is right. I too have rebuilt a good number of transmissions, and have specifically used GL-5 in all of them unless another type fluid was specified. I have also noted that some of the same Asian models used different fluid depending upon the vehicle manufacturer. Example: GM used Dexron ATF in their Asian series while Jeep used GL-5 gear oil. With the number of Jeep AX-15s I have seen crashed because of insufficient front bearing lubrication I have often wondered if possibly the Dexron might have actually been better. Who knows?... but for the most part I would stick with GL-5.
 
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