So after researching around I've found 1000 different answers. My 05 FXD has a probably never seen a primary case or tranny fluid change (new to me, so I rather do it to be safe). These thoughts are prompted by the bike not wanting to downshift into 1st when moving, giving me a grinding sometimes, so i've stopped doing that unless i'm below about 10mph and I need to start moving again. And occasionally it doesn't like to find neutral or shift smoothly into 2nd gear.

so the question, what should I actually run in the primary case and the transmission. I have easy access to 75W-90 Synthetic gear oil and the high quality ATF VI fluid, but that may not be what's best.

Teach a newbie if yall don't mind.

 

Answers will vary on this topic. I run Delo400 15W40 in my Primary w/ no issues but some run 20W50 oil as well.

 

"what should I actually run in the primary case and the transmission".

My recommendation would be, #1. Red Line 42904 V-Twin Primary Case Oil. and #2. Red Line 42804 V-Twin Transmission Oil.

 

 

No matter what tranny oil you're running, it's going to grind under those circumstances (downshifting into first while moving above 10 mph.) For the record, Mobil One V-twin in both holes is effective, simple and easy to find.

 

I'm disappointed. I thought this thread was about sex.

 

It is, you forgot to use your Decoder Ring (assuming the moderator let you have one.)

 

This. 100%.

 

Aside from the never ending debate on which oil to use, you should plan on doing a complete clutch adjustment when you're done. I don't downshift into first while moving but if that's your style it may be easier with the clutch set up properly.

 

Is this an oil thread or a sex education 101