Here is the image for a 2018 Softail:

 

So I think I figured it out. I stopped at autozone by work and picked up some Lucas gear oil, 85w140. Figured that would be okay since the gear oil Harley is selling now for trans/ primary is 80w140. Had to do on jiffy stand since didn’t have a helper but added a couple ounces and then retightened using a torx bit on a screwdriver. Even with same gasket, doesn’t look like any new leaks on way home. I’m never going to use electric screwdriver on that again. I think that was problem. Wrong sequence/ over tour queue. Also noticed a few fuel drops from under seat, but from what I’ve heard, that’s kind of normal.

 

I don't have an 18 M8 engine but are there 2 or 3 holes? For the twin cam the primary was a 10w-40 NON energy conserving and the transmission uses the gear oil. Yes the method in post 10 will get you close and at least you can verify you are not dry but servicing with the correct amount is the proper way, not by visual level.

 

The bike has to be straight up to set the level per the illustration.

 

Make sure that gear lube does not contain friction modifier for limited slip differentials, if it does it is not the right lube for you primary.

A lot of the 75-85 w140 gear lubes out there are designed for limited slip pumpkins, so be careful with the assumption that all 75w140 gear lube is the same...

 

That is just plain ridiculous.

The visual method will get you to the exact level as required in the Factory Service Manual.

The only objective is to get the lube to the correct level, not fret about 32 oz, 48 oz.etc...

 

Survey says....eeerrr...wrong answer. Imagine this ...do you think you drain the same exact amount each time you do the primary? So let's say you just fill it each time with 36 ounces but when you drain you're only getting 32...after a few changes you'll be over filled. It's your bike you do as you like but I like checking mine by looking...just like when I fill the tranny and crankcase...i look at the dipstick and I don't just drop in 3.5 quarts. To the op...carry a few basic tools with you and you could have checked you primary level in about 2 minutes. But what the hell do I know?

 

Ideally the primary fluid should meet JASO MA2 specifications for clutch performance. This will give the highest torque holding capacity.

 

Most people, including myself, find the HD Formula+ to be the best choice.

No gear lube in the Primary!

 

Surveys are like "I read it on the internet" and just as reliable. Oh wait, this is the internet so it must be true.

The OP issue was the primary leaking and I'd like all these experts to show me a picture of a dipstick on a primary. OP also made reference to adding 85w-140, gear oil to the primary and a bunch of maintenance wizards cautioning about friction miodifiers for gear oil. WRONG lube to the WRONG hole.

I do my own servicing and am consistent with my procedures when I service them. I also have REAL HD service manuals that I use for servicing guidance. I add the prescribed amounts and never had any clutch, or shifting issues. Only been working on my own vehicles for several decades but what he hell do I know?