Noisy 2008 Dyna Primary

The primary on my 2008 Dyna has been a little on the noisy side for some time now. Oh, it’s not so bad, just a little annoying intermittent noise, sort of resonating in the primary case, and only at low-speed deceleration. Hard to describe, as those noises tend to be.

The other day I was doing some interval service on the thing anyway so I decided to open it up.

Everything looked fine, I think. The chain looks great, no burrs or signs of any abrasion. This primary has the automatic tensioner, and its shoe looks great, too. No grooves or other signs of wear. If I press down on the bottom of the chain, simulating the forces of deceleration, I get about a half-inch of deflection, maybe a little less. There’s no specification for that in the service manual but it seems reasonable to me.

These images of the innards are clickable for more detail.

2008 Dyna Primary
2008 Dyna primary showing the automatic tensioner.

The only thing that might seem a little questionable to me is the toothed ramp at the bottom. There’s a toothed block that rides up the ramp with the help of a spring on the right side of the block, visible to the right of the wedge-shaped block in the image above.

In the image below it appears that the teeth might be a little buggered up. I could see that happening, maybe, under seriously hard deceleration. After all, the levers that translate the downward force to a force against the teeth would serve to amplify that force, and how much surface area could those teeth offer against those forces?? Well, it could happen…

Block and Ramp
Block and ramp detail, showing possible wear.

Trouble is, I’ve never seen a new automatic tensioner so I’ve got no frame of reference for what normal looks like. Tomorrow I’m going to be at a dealer for other reasons so I may have the opportunity to chat up a tech and/or see what a new part looks like.

Until then, if any readers have comments I’d love to hear ’em.

3 thoughts on “Noisy 2008 Dyna Primary”

  1. Been hearing questionable noise from my 08 primary as well. What ever came of this tensioner discussion at the dealer?

    1. Well, not a whole lot, Jarrod. I’ll tell you what I know.

      I learned that there have been a few automatic tensioner changes made since the introduction. My parts manual showed 39929-06A (tensioner). Because of the possible bottom plate wear I mentioned in the post (second image) I picked up a replacement part. The replacement the dealer handed me – and I didn’t check the number at the counter – 40063-05B – was called a ‘kit’

      Changing the tensioner was a fast and easy task. To my eye the replacement was identical to the one I pulled out. I read somewhere that the change that brought the number update was to the spring. And the wear I thought I saw? Once the oil was wiped from the bottom plate it looked just as good as the new one. The plastic guide was also in excellent shape.

      I’ve been a ‘Syn3 in all holes’ guy for a long time, and it’s never been a problem. In my early May interval service on the Dyna, though, I changed the transmission and primary lube back to Formula+. When I changed the tensioner I stuck with Formula+ on the refill.

      The result? It’s definitely quieter now but the noise is still there. You’ve got to really listen hard for it and the conditions have to be just right: very warmed up, very low speed (under 10-15 MPH), no-throttle deceleration. Very faint but it’s still there.

      I’ve also read that the source could be the compensating sprocket. I gave it a good visual inspection and put the torque wrench on it (it was to spec) while I was in there. It’s a good idea to do that any time you’ve got the primary open.

      I talked to the tech afterward and he seemed to feel that it was normal, no big deal. I’m inclined to agree. That said, a primary failure can go very badly so anything odd definitely calls for investigation.

      Hope that helps!

  2. I haven’t see a new one, either, but judging by the top picture, not the bottom, it looks like some teeth got buggered up.

    From the bottom picture it looks more like an allowance for some travel before engaging the tensioner, but the top looks like soft teeth got worn down.

Go ahead and say it.