C8.25 Fill question

I seem to recall something about the capacity of diffs increasing slightly using aftermarket covers (specifically RuffStuff), but could use a sanity check.

After getting the RS cover on my 8.25 last night, I proceeded to put fresh gear oil in. From the FSM, I know that with the OEM cover the rear diff has a 2.5-pt capacity. However, even after adding nearly 2 full quarts, I still couldn't feel the oil in the diff by poking my finger through the fill port and reaching down. I know it's rocked slightly back (top rearward) due to the 2-inch lift, but still I couldn't reach any oil. I stopped at what's probably 1.75-1.8 qt (approx) for fear of grossly overfilling.

For those of you running an 8.25 with RS cover, what is your customary fill amount? Have I overfilled or underfilled?

Thanks

I asked the same question last year & received many different answers,
I now just fill it until it pours out of the fill hole & I have never had a problem.

i dont think you can overfill at breathing differential... its a non pressure system, so its not like you are going to blow gaskets or seals. just fill till it pours out a little and put the plug in it like was said before

Rob, I filled my 8.25 with RuffStuff cover to the level of the fill hole. I was in front of you in Moab, did you notice any fluid leaking ? Fill 'er up and don't worry.

The "fill it until it just starts to run out the fill hole" rings familiar also. Certainly that's not hard to do - just have to go buy more gear oil (I've heard of different brands of engine oil not "playing well" together due to additives, but is that true of gear oil? Just checking).

Something else I saw in the FSM - something about an overfilled diff causing oil foaming (presumably, a bad thing or they wouldn't mention it).

Tim, out of curiosity how much did it take to fill your pumpkin?

I don't recall exactly the amount to fill the diff. I trust that Ruff Stuff located their fill hole in approximately the correct location. The cover is "deeper" so naturally the diff has a larger fluid capacity. Compare the stock cover to the Ruff Stuff cover, and eyeball measure the fill holes. As long as it is close, a full Ruff Stuff cover should bring the gear oil level (not capacity) to the correct height on the carrier.