Jump to content
IGNORED

Excess Heat in Final Drive Unit - WHY?


MontanaBud

Recommended Posts

In attempting to track down the cause of a buzzy vibration in my '04 RT, I have detected excess heat building in the final drive.  I took a different '04 RT out on a test and checked the heat at its final drive and rotor upon return, and it was much cooler to the touch after the same distance (10 miles) ridden as on my troubled bike.  To eliminate the caliper as a contributor to the problem, I removed it and went again for a test ride, but no difference noted in the vibration or the excess heat with the caliper removed. 

 

So, my question is: what would cause this excess heat in the final drive on one bike over the other?  I checked the 12-6/9-3 play on the wheel, and there is virtually none.  The rear wheel spins quietly and smoothly in neutral, even when cold.  There is no leaking fluid.  I changed the FD fluid recently and it looked and smelled fine, and there was only the normal tiny bit of muck on the FD magnet drain plug after 11k miles.  The crown bearing was replaced by the dealer about 50k miles ago.  Could it be going bad already?  Pivot bearings going bad possibly?  

 

As always, your time and advice is very much appreciated!

Link to comment

Did he re-measure for shims, or did he just use the old ones? If he used the old ones maybe it's still mis-shimmed and It's going bad again. It seems to happen at about 50K mile intervals.

Link to comment
3 hours ago, MontanaBud said:

In attempting to track down the cause of a buzzy vibration in my '04 RT, I have detected excess heat building in the final drive.  I took a different '04 RT out on a test and checked the heat at its final drive and rotor upon return, and it was much cooler to the touch after the same distance (10 miles) ridden as on my troubled bike.  To eliminate the caliper as a contributor to the problem, I removed it and went again for a test ride, but no difference noted in the vibration or the excess heat with the caliper removed. 

 

So, my question is: what would cause this excess heat in the final drive on one bike over the other?  I checked the 12-6/9-3 play on the wheel, and there is virtually none.  The rear wheel spins quietly and smoothly in neutral, even when cold.  There is no leaking fluid.  I changed the FD fluid recently and it looked and smelled fine, and there was only the normal tiny bit of muck on the FD magnet drain plug after 11k miles.  The crown bearing was replaced by the dealer about 50k miles ago.  Could it be going bad already?  Pivot bearings going bad possibly?  

 

As always, your time and advice is very much appreciated!

 

 

Afternoon Bud

 

You need to define excess heat, the final drive can run fairly hot after a distance of high speed riding so at 10 miles one might not be up to full temperature yet.

 

I doubt it is a tight bearing as a bearing would need to be extremely tight to make excessive heat (wouldn't last long at all)

 

The usual cause of final drive heat is thicker gear oil (are they both using the same gear oil type & viscosity?), or  ring & pinion friction so the hotter one could have a slightly  tighter gear lash set-up.  

 

Not much inside the final drive that will cause a vibration as the  gear/spool turns a lot  slower than the engine does, now a drive shaft or U join could cause a vibration but that doesn't  make excessive heat inside the final drive. Plus you usually feel a U joint at lower speeds. 

Link to comment

Bud,

 

Do you have an infrared thermometer??  Amazon.  $8.00  delivered.  https://www.amazon.com/Hermitshell-Etekcity-Lasergrip-Thermometer-Temperature/dp/B07PFT8JTZ/ref=sr_1_5?crid=1FZOJRXMIC2VH&keywords=infrared+thermometer&qid=1570746245&sprefix=infrared%2Caps%2C170&sr=8-5

 

After a warm up ride, quickly check the temp of the various parts of the final drive and swing arm shaft (both ends and pivot pins), then check the cat .  See if you can pinpoint (hot spot) where the excess heat is coming from.

Link to comment

You know, an awful lot of heat can come from dragging rear disc. Have you checked your disc temperature after a similar run?

 

When you say excess heat, what temperature are you talking about?

  • Thanks 1
Link to comment

What's too hot?  I'd say I could not hold my finger on it for more than one second.  The other FD was just warm.  The oils in each were the same (80-90).   As far as the dragging rear disk, I don't know what that is.  The brake disk does have a slight warp, but as I mentioned, I removed the caliper entirely from the disk rotor, and the heat generates the same, and the buzz is the same.  

 

I replaced the drive shaft about 27k miles ago.  It was (allegedly) a low miles used part, and seemed in fine condition.  I was getting a drag every 180 degrees or so when free spinning, and replacing the driveshaft fixed the problem that time. 

 

As I mentioned, the rear wheel spins freely in neutral, although with a stethoscope you can hear a slight click click sound in the FD.

 

I did use a standard axle grease on the splines.  Could that make any difference?   I guess I can look for and install another used driveshaft.  At this point, I'm just throwing money at this bike. 

 

 

Link to comment
1 hour ago, MontanaBud said:

What's too hot?  I'd say I could not hold my finger on it for more than one second.  The other FD was just warm.  The oils in each were the same (80-90).   As far as the dragging rear disk, I don't know what that is.  The brake disk does have a slight warp, but as I mentioned, I removed the caliper entirely from the disk rotor, and the heat generates the same, and the buzz is the same.  

 

I replaced the drive shaft about 27k miles ago.  It was (allegedly) a low miles used part, and seemed in fine condition.  I was getting a drag every 180 degrees or so when free spinning, and replacing the driveshaft fixed the problem that time. 

 

As I mentioned, the rear wheel spins freely in neutral, although with a stethoscope you can hear a slight click click sound in the FD.

 

I did use a standard axle grease on the splines.  Could that make any difference?   I guess I can look for and install another used driveshaft.  At this point, I'm just throwing money at this bike. 

 

 

 

Afternoon Bud

 

That does sound pretty warm for 10 miles or riding (was that from a cold ride-off?). They can get hot enough that you can't lay your hand on the housing for long but that usually takes longer than a 10 mile ride.  I still don't think that (JUST) a hot final drive could cause a vibration. 

 

Greasing the splines would make no difference in final drive heat or in any vibration. 

 

Did you phase the drive shaft  U joints correctly when you installed the drive shaft? 

 

Did your vibration start after the drive shaft install? If so then  possibly it is slightly  bent if it came out of a wrecked motorcycle.

 

 

Link to comment

Bud,

 

Couple of things to try to isolate the problem:

 

1)  Bike on center stand, trans in neutral, remove the rear wheel and turn the FD hub with your fingers to listen & feel the FD bearings.  

 

2)  With your stethoscope  listen to the bearings in the FD, drive shaft , and trans while spinning the drivetrain with the engine at idle.  A long screwdriver with the blade pressed on the housing  or case (closest to the bearing in question) and the screwdriver handle pressed on the ear works really well, too.  You will be surprised how well this works to pinpoint failing bearings and noisy tappets with a little practice.

 

3)  Could your cat (converter) be running hot from incomplete combustion in one or both cylinders??  If it is way hot it could be heating up everything in the slipstream behind it.  

 

 

Link to comment
On 10/10/2019 at 3:34 PM, Lowndes said:

Bud,

 

Do you have an infrared thermometer??  Amazon.  $8.00  delivered.  https://www.amazon.com/Hermitshell-Etekcity-Lasergrip-Thermometer-Temperature/dp/B07PFT8JTZ/ref=sr_1_5?crid=1FZOJRXMIC2VH&keywords=infrared+thermometer&qid=1570746245&sprefix=infrared%2Caps%2C170&sr=8-5

 

After a warm up ride, quickly check the temp of the various parts of the final drive and swing arm shaft (both ends and pivot pins), then check the cat .  See if you can pinpoint (hot spot) where the excess heat is coming from.

The 8.99 is for the case only, not the temp gun. 

There is a temp gun listed for 12 bucks, I have to think for 12 bucks you aren't going to get a sophisticated tool, maybe something that will give you "yup, this is hotter than that" 

 

 

  • Like 1
Link to comment

Well, Thanks, Tri750.  I'm fixin to learn that all over again as one of these is due here any minute now. I wonder how many extra units Amazon sells because of simple oversights like this.  Ugh.

Any IR thermometer will tell him "yup, this is hotter than that", and that's really all he needs to isolate the problem.

 

 

 

 

 

Link to comment
On 10/10/2019 at 9:53 PM, Jim Moore said:

Did he re-measure for shims, or did he just use the old ones? If he used the old ones maybe it's still mis-shimmed and It's going bad again. It seems to happen at about 50K mile intervals.

 

Why re-shim if it was just the bearing being swapped? I mean... it could be shimmed wrong from the factory, but based on the OP's comment:

On 10/10/2019 at 7:26 PM, MontanaBud said:

  The crown bearing was replaced by the dealer about 50k miles ago.  Could it be going bad already?  Pivot bearings going bad possibly? 

... I noticed that:

 

  • both bearings must have been changed, not just the big one
  • verify if it has the correct shims
  • if not, re-shim responsibly :)

Dan.

Link to comment
  • 1 year later...
On 10/11/2019 at 12:23 PM, MontanaBud said:

What's too hot?  I'd say I could not hold my finger on it for more than one second.  The other FD was just warm.  The oils in each were the same (80-90).   As far as the dragging rear disk, I don't know what that is.  The brake disk does have a slight warp, but as I mentioned, I removed the caliper entirely from the disk rotor, and the heat generates the same, and the buzz is the same.  

 

I replaced the drive shaft about 27k miles ago.  It was (allegedly) a low miles used part, and seemed in fine condition.  I was getting a drag every 180 degrees or so when free spinning, and replacing the driveshaft fixed the problem that time. 

 

As I mentioned, the rear wheel spins freely in neutral, although with a stethoscope you can hear a slight click click sound in the FD.

 

I did use a standard axle grease on the splines.  Could that make any difference?   I guess I can look for and install another used driveshaft.  At this point, I'm just throwing money at this bike. 

 

 

Be sure you are using the right oil quality an grade, and I think more important the oil quantity, I guess 180 ml top, no more than it.

Link to comment
8 hours ago, Cosme said:

Be sure you are using the right oil quality an grade, and I think more important the oil quantity, I guess 180 ml top, no more than it.

Morning  Cosme

 

Where did you come up with  180 ml?

 

The OP here has a 2004 oilhead not a hexhead.

 

The 2004 final drive fill level is: to lower edge of filler plug hole,  that is usually around 250ml give or take but the correct level is lower edge of filler plug hole.

  • Like 1
Link to comment

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...