I wouldnt. It's not designed for that. Gear oil would be perfect for your transmission. I recommend using a lubricant designed for primary use inside your primary. I like Spectro HD Primary Lubricant.

 

No gear oil in primary. Lots of things to use in a primary. Nothing really works any better than plain old HD F+

As for being **** changing it so often yes . But your ride it is ok to be ****.

 

I change my engine oil at 5000 miles along with my primary, tranny oil at 10,000 miles. However I can tell you this, my friend still runs the cat on his 2015 Limited and I service his bike at 5000 miles and I can tell you his oil compared to mine without the cat is night and day difference. His oil is black with a burnt smell and I've showed him this twice, I even showed him my oil at 5000 miles which still has a brown color of oil and smells like oil, not burnt. I even serviced another friends 08 model Ultra with over 6000 miles and it was night and day difference from the 15 with the cat, this tells me the engine holds a lot more heat in it which takes it toll on the oil, so 4000 might not be bad with the cat.

 

**** stars would say yes! lol

 

As black as the oil turns to in the primary after a relatively short time, it sure isn`t a bad move. Oil is cheap compared to the alternatives......

 

Opps ##