HD Sport Trans Substitute?

Aug 2, 2022
Easley, SC
So I recently purchased a 96 Sporty which calls for HD Sport Trans for the primary/gearbox lube. I've done a bit of research and the results are all over the place. It seems people use anything from 20w50 motor oil to ATF (and everything in between) all claiming no issues, smooth shifting/no clutch slippage after gazillions of miles.

Being obsolete for years now, I managed to find some online and sent to Blackstone for analysis:


Viscosity is basically 75w90.

I'm looking for suggestions for gear oils that are either pretty close to these numbers, or can be obtained with a ZDDP additive. Harley's Formula+, which they recommend, isn't even close.

Thanks in advance.
Harley Formula+
Its a gear/transmission oil. ZDDP is for engines, not transmissions or primary.
To the best of my limited knowledge on the subject no recommend gear/primary oils contain ZDDP that is why they are gear oils.
You can use engine oil with ZDDP but its not gear oil.

When you search any oil on line "results will be all over the place" and mean nothing, its just opinion.
ZDDP is actually an anti wear compound formed by zinc and phosphorus. Since HD included these elements, gotta assume they’re kinda important.

So, to clarify, I’m looking for gear oils similar to the original formula, or a suitable gear oil and/or ZDDP additive recommendations.
Your bike is a 96. GL-4 rated gear oil, is what you need: I sent you a link to purchase above. You're overthinking this.

Harley says it's appropriate for your bike.

Seems like they'd be the authority.
It does. Yet Formula+ isn’t even close in phosphorus and zinc. I read somewhere later model bikes got different (harder) gears and don’t require ZDDP. Dunno. But ya, as HD said Sport Trans for my bike, that’s what I’m trying to use.
Awesome and thanks. Will definitely check it tonight. You don’t happen to have an analysis do you?
I do not, but really doesn't matter to me. I'm sure someone out there has done it. I can tell you I used it for about 12 years or so in my 94 Sporty. Parades, funerals, going down to bike week. Lots of hot hot weather all over Florida and Georgia. Never had an issue at all.

You will have no issues with this fluid or even the Harley stuff. Price is about the same. Harley says you can even dump a quart of SYN 3 in the hole. The primary chaincase / Tranny isn't that hard on oil to be honest.
75w90 is the SAE grade... the actual viscosity flow is 16.1 cSt @ 100C which is about the same viscosity flow as 50 grade motor oil @ 100c... so technically speaking any 50 grade motor oil will meet and exceed your mileage expectations...
Except gear oil and motor oil don't have the same add pack for obvious reasons. Gear oils have more EP additives to better take the punishment of a gearbox.