Gear oil for rear axle

[Ward Duffield]

Hi Group

What is the approved, currently available gear oil for our cars' rear axles? I see a lot of acrimony over GL-4 vs. GL-5, etc.

Thank you.

[Adam H P15 D30]

GL 4 and GL 5 are important topics for manual transmissions because of yellow metals used in earlier transmissions. For that application I used MT 90 manual transmission oil and it made a noticeable difference in shifting especially cold. My transmission is a std. 3 speed. 

 

As to your question, any GL 5 90 wt. hypoid gear oil is sufficient. GL 5 is the most common now. 

 

Adam

[Tim Larson]

I've heard you should use GL 1 in a transmission. Is this incorrect?

[Adam H P15 D30]

1 hour ago, tjlarson88 said:

I've heard you should use GL 1 in a transmission. Is this incorrect?

GL 1 is kind of available.  This works better and is safe for the soft metals in the std. 3 speeds.

 

 

 

 

Edited September 16, 2019 by Adam H P15 D30

[Plymouthy Adams]

The GL1 is available for approx. 15.00 a gallon at your local NAPA and the gallon is the smaller container....even if they do not have it on the shelf, they can get it in for you fairly quickly if your local store has good management.....

[Tim Larson]

Just now, Plymouthy Adams said:

The GL1 is available for approx. 15.00 a gallon at your local NAPA and the gallon is the smaller container....even if they do not have it on the shelf, they can get it in for you fairly quickly if your local store has good management.....

I have ordered the GL1 through our Napa store to use in my 52 Mercury overdrive. It's what I will use in my 49 special deluxe too. 

[YukonJack]

My neighborhood Napa had GL1 on the shelf.

[Adam H P15 D30]

I had the NAPA GL1 oil prior to trying this, it worked fine.  After trying the MT 90, I'm glad I spent the money.  It worked much better especially cold.  Trans doesn't hold much so it's not too hard on the budget.  Your call, but sometimes it's good to open your wallet a little and blow the cobwebs out.