RDU Gear Oil Weight - 75W90, or 75W140?

[autoteleology]

I keep reading conflicting information, so I would be really grateful if someone would clarify which gear oil is the proper replacement, and why.

 

[FrankK]

The proper for the RDU is 75-90. Can't tell you why. I replaced the RTU fluid in my wife's FLEX with 75-140 Amsoil. Just my preference.

 

[SM105K]

I personally use Redline Light Weight Shock Proof in my RDU and PTU.

 

[autoteleology]

I personally use Redline Light Weight Shock Proof in my RDU and PTU.

Do you know what the difference between Redline's Lightweight Shockproof gear oil, and their regular 75W-140, is supposed to be? They cost basically the same, so it doesn't seem to be a matter of quality grading.

Also, if the default is allegedly 75W-90, why not use the Superlight?

 

[SM105K]

The LWSP and the regular 75W-140 isn't the same. They are different. Just because cost is basically the same, that doesn't mean much.

I didn't use the superlight because I was told by people I trust on other forum and from my own DD to use the LWSP. The LWSP has has been in my RDU and PTU since 69K miles. The PTU LWSP was changed again at 80k when I drilled and tapped my PTU. My car just ticked over 90k. Zero issues with either.

 

[autoteleology]

The LWSP and the regular 75W-140 isn't the same. They are different. Just because cost is basically the same, that doesn't mean much.

I didn't use the superlight because I was told by people I trust on other forum and from my own DD to use the LWSP. The LWSP has has been in my RDU and PTU since 69K miles. The PTU LWSP was changed again at 80k when I drilled and tapped my PTU. My car just ticked over 90k. Zero issues with either.

IDK, man, I know you probably know way more than me about these cars, but I just hate not understanding the reasons behind things. I have lots of hobbies that I am in an advanced level in, and too often it turns out that people who I used to think were gurus on a topic were just loud and confident. I have no reason to believe that of you, but there is a reason I always seek to trust, but verify - it's very difficult to tell the difference as a novice, and you don't really learn anything by just taking someone's word.

 

[Bluezone]

IDK, man, I know you probably know way more than me about these cars, but I just hate not understanding the reasons behind things. I have lots of hobbies that I am in an advanced level in, and too often it turns out that people who I used to think were gurus on a topic were just loud and confident. I have no reason to believe that of you, but there is a reason I always seek to trust, but verify - it's very difficult to tell the difference as a novice, and you don't really learn anything by just taking someone's word.

I believe oil shear strength, temperature range (oil molecules breaking down because of these 2) and drag/tolerances (fuel economy) are the main reasons for the RDU and PTU oil recommendations.

 

[SM105K]

IDK, man, I know you probably know way more than me about these cars, but I just hate not understanding the reasons behind things. I have lots of hobbies that I am in an advanced level in, and too often it turns out that people who I used to think were gurus on a topic were just loud and confident. I have no reason to believe that of you, but there is a reason I always seek to trust, but verify - it's very difficult to tell the difference as a novice, and you don't really learn anything by just taking someone's word.

You have every right two research and this topic has been beaten to death over a couple of forums. However, most of the high horsepower guys and drag racers use LWSP in their PTU and RDU's.

However I have real results as well. This was/is accumulated in two extreme climates. I have run my SHO with LWSP in my RDU and PTU for documented long range (300 mile +) highway runs averaging roughly 95 mph in 110+ degree heat. Works great.

I have also done some cold weather driving as well and everything in between. I will continue to use LWSP because it checks all of the boxes for myself.