85w140 rear end oil in my all original 67 327/300

[Terry H.]

No slip, no noise, is this okay vs 75W90 + additive

[Keith B.]

Re: 85w140 rear end oil in my all original 67 327/300

80-90 gear oil

[Duke W.]

Re: 85w140 rear end oil in my all original 67 327/300

85W-140 is for HD truck axles, like so-called "big rigs". The current spec that replaces the original Mil-L-2105D is SAE 80W-90 GL-5. Are you a more experienced lubrication engineer than those who specified the axle oil and managed all the durability testing...?

I didn't think so.

Duke

[Jack H.]

Re: 85w140 rear end oil in my all original 67 327/300

If it has a posi differential (aka limited slip), you definitely want the GM additive.

[James W.]

Re: 85w140 rear end oil in my all original 67 327/300

I use the Lucas Oil 85w-140 gear oil plus the GM additive that was recommended by Gary Ramadei a foremost Corvette differeintial and trailing arm rebuilder. He's put on seminars at many large Corvette events. I don't think he would steer anyone wrong. My rebuilt '65 differntial is quite and exibits no problems using this lube.

James

[John F.]

Re: 85w140 rear end oil in my all original 67 327/300

These two appear to be the same thing. I don't think you need to add the GM additive with them.

[Gary R.]

Re: 85w140 rear end oil in my all original 67 327/300

You can use either a 90 wt gear oil, non-synthetic or the Lucas 85-140 also non-synthetic. You can also debate brand names, wts, etc. Literally 100's of vette diff's I've built over the years - all with tuned Posi's, solid steels, use the Lucas 85-140. I use in every level of diff I built from stock 10 to 12 bolt vette, from 250hp-900 hp. Never had any issue with the oil, use 2 bottles of the current GM additive- again you can go with other brand names if you like but I stick with what I know works. Change the oil after a rebuild at 500 miles and heat cycling, change as a PM around 8-10k miles.

I can't say anything about the Castrol gear oil.

Interesting note, I took in trade a super 10 diff I built 10 years ago that was filled with the Lucas oil and never installed in the car. I had some reservations before I opened it up fearing the diff sat so long the oil ran off the metal above the oil level line and I would see rust. To my surprise the diff looked exactly as it did 10 years earlier when I built it. No surface rust, the lucas oil was clinging to the metal, where common gears would have rolled off and dried out the metal over that time. Unless they change the chemistry, as GM did with the additive a few times, that is what I will use.

[Gary R.]

Re: 85w140 rear end oil in my all original 67 327/300

Hi James
Glad to hear you're on the road. Enjoy the car.