Rear end Gear lube

[Dave Gantz]

Originally Posted by Mike Rietow

GL-5 is the key ingredient to look for drag racing.

Hi Mike, just wondering, why?

[Rory McNeil]

Originally Posted by Dave Gantz

Hi Mike, just wondering, why?

I`m curious as well. I had been told that the main difference between GL-4 and GL-5 gear oils, was that the GL-4 was designed for use in manual transmissions with "yellow metal" syncronizers, like brass/bronze, and the GL-5 was for syncros with paper or carbon fiber linings. It seems that finding GL-4 gear oil is not as easy these days, GL-5 seems far more common. For the Toploader 4 speed in my street car, I have been using GL-4 Brad Penn, seems most of the major oil companies have just GL-5.

[SSDiv6]

Originally Posted by Rory McNeil

I`m curious as well. I had been told that the main difference between GL-4 and GL-5 gear oils, was that the GL-4 was designed for use in manual transmissions with "yellow metal" syncronizers, like brass/bronze, and the GL-5 was for syncros with paper or carbon fiber linings. It seems that finding GL-4 gear oil is not as easy these days, GL-5 seems far more common. For the Toploader 4 speed in my street car, I have been using GL-4 Brad Penn, seems most of the major oil companies have just GL-5.

Rory,

GL-5 has a higher EP (Extreme Pressure) rating than GL-4 and it offers a higher shock load protection when you have a high angle of gear contact. GL-4 gear oil, no matter the viscosity, has half of the sulfur/phosphorous additive that gives the shock load protection.

Nevertheless, because of the different angle of gear contact and softer contact material, on a manual transmission, this same additive used on the GL-5 gear oil effects the syncros and other soft metal components by fretting the contact surface.

[Eman]

Originally Posted by Rory McNeil

I`m curious as well. I had been told that the main difference between GL-4 and GL-5 gear oils, was that the GL-4 was designed for use in manual transmissions with "yellow metal" syncronizers, like brass/bronze, and the GL-5 was for syncros with paper or carbon fiber linings. It seems that finding GL-4 gear oil is not as easy these days, GL-5 seems far more common. For the Toploader 4 speed in my street car, I have been using GL-4 Brad Penn, seems most of the major oil companies have just GL-5.

I've got some Ford gear oil F2ZZ-19C547-A which should be GL-4 80W Ford parts oil Ford spec. M2C83-C. I've got 4 or 5 quarts I'd sell.

[Mike Rietow]

Originally Posted by Dave Gantz

Hi Mike, just wondering, why?

I run US Gear, when I asked what they like to see in gear oil, they said GL-5 is the key ingredient drag racing.

Valvoline High Performance gear oil is GL-5

Valvoline regular gear oil is not.

Here's a mention in dragzine confirming they're recommendation. No technical terms though, I couldn't find anything other than this.

I just use $4.97 Valvoline GL-5 80w 90. Ford 9" Strange chunk, I've had several different gear ratios in. 3.90, 4.10, 4.33. 4.56, 5.00, 5.29

3200 lb 23 n/a sbc 1.27 60 ft

https://www.dragzine.com/news/lubric...r-in-gear-oil/