My 1975 Ford Capri demands SAE 90 for the gearbox and diff ( non LSD ) ,can I use 75w90 instead?
75w90 instead of SAE 90
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Thanks for the reply but I've already bought a few quarts of Ford motorcraft 75w90 for fairly cheap
Originally Posted By: UrS4
Just be aware of brass synchro compatibility (the gl 4 spec)!
That's right: GL-4 ONLY (must NOT be a dual-rated fluid that also meets GL-5 spec) for the gearbox if it has yellow metal synchros. GL-5 is for the differential. Some manufacturers of gearboxes that were originally spec'd for GL-3 and GL-4 fluids now recommend synthetic 10w40 engine oil be used instead (viscosity is equivalent to a 75w90 gear oil). An example is the common Aisin AX-15 used through the 90s in Jeep Cherokees and Wranglers.
Just be aware of brass synchro compatibility (the gl 4 spec)!
That's right: GL-4 ONLY (must NOT be a dual-rated fluid that also meets GL-5 spec) for the gearbox if it has yellow metal synchros. GL-5 is for the differential. Some manufacturers of gearboxes that were originally spec'd for GL-3 and GL-4 fluids now recommend synthetic 10w40 engine oil be used instead (viscosity is equivalent to a 75w90 gear oil). An example is the common Aisin AX-15 used through the 90s in Jeep Cherokees and Wranglers.
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Thanks for letting me know i had no clue at all about this! how can i know if it's GL4 or 5?
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I recommend Castrol syntrans too, it is gl-4 only
Originally Posted By: FordCapriDriver
Thanks for letting me know i had no clue at all about this! how can i know if it's GL4 or 5?
The label should say. Many gear lubricants say "meets GL-3, GL-4, and GL-5." Well, that would be good if GL-5 weren't potentially damaging to some (if not MOST) manual transmissions.
Fluids like Redline MTL, MT-90, Royal Purple Synchromax, GM Synchromesh compatible fluids, etc. are typically no higher than GL-4 rated, and are good for manual transmissions. Sychromax and Synchromesh fluids are for manual transmissions that take ATF-weight fluids. MT-90, MT-85, etc. are for transmissions that need heavier gear oil.
But for the rear end, you need a hypoid gear (GL-5) lubricant.
Thanks for letting me know i had no clue at all about this! how can i know if it's GL4 or 5?
The label should say. Many gear lubricants say "meets GL-3, GL-4, and GL-5." Well, that would be good if GL-5 weren't potentially damaging to some (if not MOST) manual transmissions.
Fluids like Redline MTL, MT-90, Royal Purple Synchromax, GM Synchromesh compatible fluids, etc. are typically no higher than GL-4 rated, and are good for manual transmissions. Sychromax and Synchromesh fluids are for manual transmissions that take ATF-weight fluids. MT-90, MT-85, etc. are for transmissions that need heavier gear oil.
But for the rear end, you need a hypoid gear (GL-5) lubricant.
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Originally Posted By: Popsy
I recommend Castrol syntrans too, it is gl-4 only
Very good fluid and widely available in Europe.
Another one is Shell Spirax S4 G 75w-90 GL-4
I recommend Castrol syntrans too, it is gl-4 only
Very good fluid and widely available in Europe.
Another one is Shell Spirax S4 G 75w-90 GL-4
Originally Posted By: FordCapriDriver
My 1975 Ford Capri demands SAE 90 for the gearbox and diff ( non LSD ) ,can I use 75w90 instead?
I would use 75W-90 GL-5 in the differential and 75W-90 GL-4 in the transmission. The EP additives in the GL-5 has been known to mess with synchros in some manual transmissions.
My 1975 Ford Capri demands SAE 90 for the gearbox and diff ( non LSD ) ,can I use 75w90 instead?
I would use 75W-90 GL-5 in the differential and 75W-90 GL-4 in the transmission. The EP additives in the GL-5 has been known to mess with synchros in some manual transmissions.
Rumors spread, Eneos GL5 75w90 can be used in gearbox that needs GL4. I read about that in rx8 club forum. I forgot the link. Maybe u can check it. This oil (rumors) slightly contains GL4's EP additive so i will not harm ur gearbox.
Google it for further details
Google it for further details
Yup, some GL5's are actually also safe for brass synchros and they are usually dual rated, E.G. GL4/5 or GL4+5.
If in doubt then try find the copper corrosion test in the datasheet, if the result is "1a" or "1b" then you should be good (1a is better than 1b)
If in doubt then try find the copper corrosion test in the datasheet, if the result is "1a" or "1b" then you should be good (1a is better than 1b)
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