This is a 1970 Ford differential. GL5 cannot be used as it is harmful to any yellow metal.
Problem finding conventional 75w90 gl4 gear oil
- Thread starter NewMex
- Start date
Correct. Which is why you should use 80w90, if you want conventional. 80w90 GL4 is not any thicker than 75w90 GL4. The difference exists, but is impossible to notice in 99.6735% of real world situations.
Or check Redline, they have multiple GL-4 offerings. MT-90 being my favorite.
Is this a passenger car or pickup truck? I'm not aware off any Ford differentials of that era with yellow metals.
The only 75w90 GL4 available on the shelf of a US store is Liqui Moly 20012. Napa carries it. Search for LM20012
Looks like it's dual rated (GL4/GL5) which opens up majority of gear oils on the shelves as being compatible, since they are dual rated too. Valvoline comes to mind, readily available.
That's not true at operating temperatures of 100C.
And like that is a bad thing.
Attachments
While the other oils you mention can be used in the OP's differential, this L-M is the only one that is safe to use in a manual transmission.
Not gl4
The only non synthetic GL-4 75W90 I've found is that Ravenol TSG 75W90. Other than that you're gonna have to buy full synthetic 75W90 manual transmission fluid like redline MT90.
www.ravenol.de
RAVENOL Getriebeoel TSG SAE 75W-90
RAVENOL Getriebeoel TSG SAE 75W-90 is a synthetic multi-purpose transmission oil for maximum duty manual transmissions. RAVENOL Getriebeoel TSG SAE 75W-90...
www.ravenol.de
MolaKule
Staff member
Me neither.
I think it would be advantageous for you to review the Operator's manual for that vehicle (which you have not stated) and see if it requires a GL-5.
If it requires a differential fluid of a 90ish grade and a GL-5 rating, then any 75W90 differential fluid will suffice.
Redline is all synthetic, no conventional
Yeah, I had my eye on this one.The only non synthetic GL-4 75W90 I've found is that Ravenol TSG 75W90. Other than that you're gonna have to buy full synthetic 75W90 manual transmission fluid like redline MT90.
RAVENOL Getriebeoel TSG SAE 75W-90
RAVENOL Getriebeoel TSG SAE 75W-90 is a synthetic multi-purpose transmission oil for maximum duty manual transmissions. RAVENOL Getriebeoel TSG SAE 75W-90...
Thanks
MolaKule
Staff member
Is it of a Hypoid design? In what vehicle is this differential installed?
Aparently that was the product code for straight SAE90 gear oil, so 80W90 should work fine.
- Joined
- Sep 21, 2020
- Messages
- 452
I wonder what API GL classification was in use at the time that car was manufactured? I would think it was GL-3?
Which was superseded by GL-4.
DO NOT BE CONFUSED.......... GL-4 WAS NOT SUPERSEDED BY GL-5!
Which was superseded by GL-4.
DO NOT BE CONFUSED.......... GL-4 WAS NOT SUPERSEDED BY GL-5!
As others have stated and what I've found from googling, doesn't look like there's any reason not to use GL-5 in it, I can't find an exact TSB or anything but it appears that Motorcraft 80W-90 Premium Rear Axle Lubricant is what supersceded the old SAE90 Hypoid fluid and the new Motorcraft fluid is GL-5, It looks like GL4 is probably not needed and any GL-5 75W90, 80W90, 85W90, or SAE90 would work.
MolaKule
Staff member
A GL-4 does not have the Extreme Pressure (EP) chemistry needed to prevent excessive wear from the high loading in a Hypoid differential.
A GL-5 rated differential fluid in grade 75W90 or 80W90 will more than suffice.
A GL-5 rated differential fluid in grade 75W90 or 80W90 will more than suffice.
- Joined
- Jun 13, 2013
- Messages
- 3,082
I suggest Motorcraft® Full Synthetic Manual Transmission Fluid, SAE 75W-90 gear oil, XT-M5-QS
MOTORCRAFT XTM5QS Transmission Fluid | RockAuto
RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.
www.rockauto.com
