When I questioned why 5th gear was so noisy on an 09 Heritage I was told that it was normal. But why is it so loud and if its normal, why have they gone to a Helical Cut 5th gear for 2010?

 

The noise you hear is normal for a straight cut gear. Sorry, but that is just the mechanics of the matter. Although straight cut gears are noisey, they are stronger than helical cut gears. It only took HD four model years to figure out that customers want a quiet gear box. The noise you hear will not affect the trans life. If you want to quiet it down a bit, fill the trans with a heavier oil. I use Redline Heavyshock Proof in mine and has made a big difference.

 

Why only 5th?

 

because only 5th gear is straight cut... I went round and round with the service guy about it... .turns out to be that's what the engineers designed the gearbox.

 

1st is straight cut too....

 

The idea was for first and fifth to be straight cut. First is stronger for launching and fifth for passing . Since the 96" don't have a chance at hurting either helical or straight the helical 5th is now used to silence the bitching in regards to clatter and whining sounds in the pre 2010 six speed. Sometimes I have to wonder where moco comes up with their design ideas.
Ron

 

but first doesn't have that annoying clatter like its abouyt to jump out of gear in the bottom half of the rpm range. but at least you only hear it when the windshield is on.

 

I got my V&H Shortshots and that 5th gear whine seemed to go away.

 

Not enough load to deflect the shafts in first, or influence of the other helicals causes the problem in fifth.
Ron

 

sounds like someone needs louder pipes....... I don't hear mine either, but then I don't wear a helmet nor a windshield and have loud pipes, I'd say it's fixed.