Getting ready to do my 1000 mile oil change. I'm changing to synthetic, (Mobil 1). Gonna use 15w-50 in the engine. Have been told to use 75w-90 gear oil in both the trans and primary. Sound right?

Thanks,
Rick

 

i run gear oil in the tranny and 10w40 in the primary. (amsoil)

 

I run the 15W-50 in the primary and the crankcase and the 75W-90 in the transmission. However, some folks use 15W-50 in all three.

 

Which model HD?

 

05 Road King Classic

 

Don't put the 75w-90 gear oil in the primary, it's for the tranny only. Run some 10w-40 in the primary, if you don't use the 15w-50 there. My clutch thinks the 15w-50 feels too heavy. At least that is what it told me the other day.

 

Ok, why not use the gear oil. The reasoning I've heard for using it, is that the primary contains gears/chains that tend to fling motor oil off. The gear oil supposedly stays on the parts better. This info is coming from an engineer. Not saying that he's right, just want to know why, if he's not. Also, checked Spectro oils web page, they also make a gear oil that they recommend for the primary.

Thanks,
Rick

 

I'm kinda new to HD, but, the primary also houses the wet clutch. I doubt if the clutch will ever properly disengage if the oil is that heavy (75-90).

 

Ted,

I went ahead and put the 75w-90 in the primary. Everything seems fine so far. The guy that recommended it has over 20,000 mile on his RK and he's been using the gear oil since 1000 miles.

Thanks,
Rick

 

Sounds good, Rick. I was just informed by Red Line via email that Superlight Gear Oil is too light for my HD tranny. They recommend heavy - guess I'll change. It did seem pretty light as it went in.