Speedometer quit? Check these things! - Snowmobile Forum: Your #1 Snowmobile Forum

**BC_Dan** · 12-08-2007, 01:54 PM

Most snowmobiles have a mechanical gear driven cable that drives the speedometer head to indicate speed and miles driven. The speedometer gear is usually turned by a pressed wire speedometer key, usually driven by the end of the driveline. The key is inserted in a bushing or square hole in the driveline and a similar hole in the gear adapter.

When the speedometer fails, there can be several reasons for failure.

Failure of the speedometer itself.

Speedometers are pretty reliable, unless they are subject to damage or immersion. If all other checks are ok, it may be the speedometer. Repair to speedometers is expensive. It will probably be cheaper to obtain a different speedometer for the sled.

Failure of the cable

The cable that goes from the gear adapter to the speedometer is subject to wear and tear. Kinks or physical damage can render the cable inoperable. If the cable can’t turn, it can’t drive the speedometer. Surface damage to the outer sheath of the cable can allow moisture to penetrate to the interior of the cable, causing rust, which can also freeze up the cable. Lack of lubrication can also cause the cable to stop operating properly. Sometimes removing the cable and cleaning and lubricating the cable and sheath can bring a bad cable back to operating condition.

The cable is easy to test. Remove the cable from the speedometer gear adapter and attach the cable end to a drill. Run the drill and see if the speedometer moves. If so, the cable and speedometer are good.

Failure of the gear adapter

The gear adapter that the cable is attached to is a mechanical device and is lubricated by the grease fitting on the gear adapter. If it does not get adequate lubrication during maintenance of the sled, it can freeze up.

To test, remove the gear adapter from the sled and attempt to turn the gear with a small screwdriver from where the key adapter inserts on the driveline side of the adapter. As you turn the screwdriver, the gear inside should turn and you will see rotation of the speedometer end of the gear adapter. If the gear adapter does not turn easily or you do not see rotation, the adapter is suspect. Sometimes cleaning and lubrication will be all that is necessary.

Failure of the driveline to gear adapter wire key

The wire key that drives the gear adapter will sometimes shear, not allowing the rotation of the driveline to drive the gear adapter. This is the most common reason speedometers quit working, and the most critical to fix the cause. The driveline of the sled has bearings on both ends. One is in the chaincase, the other is held by two flanges on the PTO end of the driveline. The driveline PTO end bearing is usually a sealed bearing and does not get lubrication when the gear adapter is greased during maintenance. The inside of the bearing is open to the tunnel and is subject to all the snow, dirt, debris, and elements that the sled is driven through. Over time, the bearing starts to fail. The failure of the bearing creates a condition where the hole in the end of the driveline and the hole in the gear adapter are no longer in alignment. The movement of the driveline will shear the speedometer drive key. The speedometer gear adapter is no longer driven, and the speedometer stops working.

The problem is not the speedometer or the cable or the gear adapter. It’s the bearing failing. If the failed bearing is ignored and the sled continues operation, the bearing will fail catastrophically. The bearing race and balls fail, resulting in the ball bearings falling out. Now there is no bearing surface for the driveline. Continued operation will result in the weight of the sled resting on the driveline end, causing damage to the driveline and to the flanges holding the bearing. Eventually, the damage will shorten the driveline to the extent that the driveline can drop completely out of the bearing and into the track. If that happens, the gear and chain on the other end of the driveline pivot out of alignment. Damage to the tunnel, track, gear, chain, and chaincase can be very significant. If the failure happens at speed, serious injury to the driver of the sled could occur.

If the speedometer quits working, make sure what the cause is. Use the failure of the speedometer as an early warning sign of impending driveline bearing failure.

beavernutts · 12-08-2007, 02:34 PM

Great info there thanks for posting.

FoxLakeRider · 12-11-2007, 04:04 PM

Nicely done!!

tmorriss · 12-15-2007, 01:27 PM

One more thing it could possibly be (and I know this from experience unfortunately), is a broken driveshaft. Check the driveshaft to make sure it is not broken somewhere between the the driven clutch side and the chaincase side.

harofreak · 01-08-2008, 11:22 AM

this is some very useful info, man. i just found out that the bearing on the clutch side(the speedo side) was starting to wear pretty bad, and the speedo has not worked since i bought the sled, about 7-800 miles ago. i had never really given it much thought, but when i took it apart to change the track, i noticed that the wire key was sheared, so i may or may not replace it, i have no need for a speedo, as it is just a 92 ac 340, not super fast, but if i had not noticed, there may have been significant damage to the sled in another couple hundred miles
great info

cjone782000 · 01-21-2008, 08:51 AM

lol i wish i saw this when my speedo failed....lol

ramblnman · 01-27-2008, 10:27 PM

good post! if only most snowmobilers knew this they could have saved loads of dough.

2Panthers · 02-16-2008, 05:39 PM

Hey everyone...

Take Dan's advice above to get your bottom shaft clutch-side bearings checked out if the speedo breaks.

My '96 Panther's speedo broke at the beginning of the month halfway through my trip in Grayling, MI area. I continued to drive it another 100 miles, and could NOT detect anything else wrong with the sled at all (other than the bad speedo).

I started Googling the topic when I got home and came across Dan's post. I just ran this sled down to my mechanic who quickly pulled the clutch and the gear adapter and showed me that the bearing on the shaft behind the gear adapter was shot.

HOPEFULLY my drive shaft is okay. Those alone are around $200 brand new he told me. 440 Panther drive shafts are harder to find on Ebay, etc. due to the lower number of lower powered sleds out there that used this style of shaft. He thinks it should be okay, but I'm keeping my fingers crossed anyways!

In any case, DON'T IGNORE a broken speedometer when it happens. If you HAVE to keep riding, pull the gear adapter if you can, and check that bearing!

Thanks again Dan!!!!

-2P

**BC_Dan** · 02-16-2008, 05:45 PM

Glad to help, I've had 3 of 'em go so far

dhorn 14 · 02-18-2008, 11:42 PM

If your speedo goes out on the trail, a quick check of the drive shaft could tell you if the bearing is out *caution*-the drive shaft may be hot- I figure I road 9 miles w/out a speedo and when I stopped to check it out the chain side was iced over and the speedo side waas untouchable. $30 bucks for a bearing is way better than replacing the drive shaft and chain case. Don't ignore the "little stuff"!!

SShooterZ · 04-20-2008, 12:07 PM

I know this one has been quiet for awhile but how difficult is it to change the driveline bearings?

Is this something that should be a standard maintenance practice after so many miles?

**RJ Gleason** · 04-21-2008, 04:51 AM

Some sleds will run a long time with no bearing problems and others won't.
A good rule of thumb is to change the bearings every 3000 miles, or when the speedo quits.
Always change them in pairs as well.
An inspection of all the bearings in the drive train should be part of your annual maintenance program, whether is be the fall setup or spring end of season pre-storage.

Bush_aholic · 10-22-2008, 02:24 AM

Dropped the drive line in my old Phaser due to this, and My buddy dropped his on his Mountain Cat 800 last year in the middle of nowhere he got towed out with a sleigh under the track by a Scandic for about 50km to the trailer, everything was shot chain case and all

cjone782000 · 11-06-2008, 06:58 PM

my sled seized right after my speedo failure...maybe 50 miles? 150 close to that

Snohorse · 11-16-2008, 01:07 PM

When I bought my sled the speedo wasn't working.. To change the bearings, do you need to remove the engine?

ramblnman · 11-16-2008, 01:37 PM

no not usually,it is not always a bearing, might just be a speedo cable or keyway ,what is it for a sled?

**RJ Gleason** · 11-16-2008, 02:23 PM

Quote:

Originally Posted by Snohorse

When I bought my sled the speedo wasn't working.. To change the bearings, do you need to remove the engine?

No, you do not need to remove the engine.

Snohorse · 11-18-2008, 03:24 PM

Thanks guys, I found the speedo gear, I will take it out and check what\s going on. thanks again

deeredoug · 01-21-2009, 08:36 PM

What if you have a sled without a speedo? Is there a way to check if the bearings are OK? Thanks.

**BC_Dan** · 01-22-2009, 12:03 AM

About the only way would be to inspect the bearing. The more miles the sled is ridden, the more wear on the bearing. Usually, when a bearing fails, it does show it's failing a while before it completely comes apart. Any up/down movement on the drive shaft should let you know bearings are going, as well as any abnormal noise coming from that area.