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The service hole is located (engineered) to be in a location which provides optimum oil and atmospheric overhead for venting.
Gear oil should reach the bottom of the service port hole. Insert your pinky into the open service hole. Bending your finger downward slightly your pinky should come into contact with gear oil. If you can't contact gear oil w/ the tip of your pinky, you are low. There is nothing wrong with gear oil which runs out of the bottom of the service hole as long as you're on level ground.
The service hole is located (engineered) to be in a location which provides optimum oil and atmospheric overhead for venting.
Gear oil should reach the bottom of the service port hole. Insert your pinky into the open service hole. Bending your finger downward slightly your pinky should come into contact with gear oil. If you can't contact gear oil w/ the tip of your pinky, you are low. There is nothing wrong with gear oil which runs out of the bottom of the service hole as long as you're on level ground.
Then I definitely need to add some because I had my pinky in up to the second knuckle and even when I bent it down as far as I could, it was still dry. I'm thinking Valvoline 75/90 synthetic with the limited slip additive.
Then I definitely need to add some because I had my pinky in up to the second knuckle and even when I bent it down as far as I could, it was still dry. I'm thinking Valvoline 75/90 synthetic with the limited slip additive.
You really don't want to mix synthetic and conventional. There are conventional gear oils with a friction modifier added also.
If not enough fluid, the atmosphere above the fluid is greater (increased) than normal forming more condensation and this moisture needs to be released.
You'll see more condensation in the form of moisture being released from the differential vent tube when the differential fluid is low & that's simply because you're building & retaining more heat in the differential than is normal. Again, generally creating premature degradation of the rubber contained in the pinion gear e.g. rubber breakdown/cracking. Regarding you knowing gasket is good because of what it looks like on the outside - I'm suspect of your observation & I'm further suspect since your fluid level is that low. Changing differential fluid & the gasket takes the same amount of time as changing your engine oil. 113K miles on a rear differential which you cannot validate has ever been changed (since you didn't do it yourself) is highly suspect. Your car, your decision.
I just measured my 1971 8.5” 10 bolt and the bottom of the fill port is 2 cm (.75”) above the top of the rib. Dunno what oil volume that translates to, but there’s plenty of oil in there to lubricate everything.
I reached out to the previous owner and the fluid has been changed. I'm going with Valvoline 75/90 conventional with the additive. What's the easiest way to put it in? Can I pour straight from the bottle or will I need a pump?
