T10/Toploader Gear Lube

[robib]

What people using for gear lube in their transmissions. What about GL5?

[Joe Travers]

I'm currently running Sta-Lube GL-4 but may switch next change.
T-10 guru Paul Cangialosi says GL-5, no problem unless it gets to boiling point. Don't see that happening.

Joe

[comethead]

I couldn’t find a GL4 oil locally for my Toploader so I got this stuff from Summit https://penngrade1.com/products/gear-lu ... ae-80w-90/

Smooth shifting, no issues

[robib]

I was just curious as to what people might say. I had my T10 out of my car a few years back to correct it from jumping out of 2nd gear. Went to NAPA and picked up 80/90 weight gear lube and filled my tranny. Everything seemed fine. Fast forward to last year and I became aware of the gear lube you might grab off the shelf at your favorite parts store. It has a rating of GL-5 , which is the latest and I looked it up and found it SHOULD NOT BE USED in synchromesh transmissions. I found that interesting and bought GL-4 for a Toyota Hilux tranny I was using. In the meantime, I was having difficulty shifting my Comet from 2nd to 3rd and 1st to 2nd was getting progressively harder. It seemed like my Hurst shifter was the problem. I have other cars, so the Comet does not get driven that often. Also when cold the tranny seemed to shift fine, but when hot, it shifted terrible to the point where I had to double clutch to shift up from 2nd to 3rd. I looked on my shelf and found the bottle that I had used to fill the T-10. Yup, GL-5. Put the car on the lift and drained the tranny (left it for a week) and filled it with GL-4. All my problems are gone now. Anyone who says GL-5 is OK to use in a synchromesh should rethink that. My GL-5 bottle even says NOT TO USE in synchromesh transmissions.