Is the chaincase a weak spot?

[IDspud]

That absolutely explains why I had stump in my case and case in the stump.

 

[Sage Crusher]

If your going to replace the btm gear- we always suggest to clients and install the manual tensioner.
Great piece of mind and something you can adjust even though many set- it and forget it...but then again leading the horse to water scenario.....

 

[sno*jet]

IMO what happens to the Cat chain cases that blow that are not a result of impact damage:

They are made of magnesium. Magnesium has a much higher rate of thermal expansion than aluminum. Magnesium expansion coefficients vary widely depending on the alloy, but lets say you pick one in the middle of the range. I haven't measured how far apart the jack shaft and track shaft are C-C in the sleds, but for argument sake assume 18". Put that together and that 18" distance increases by up to 1/16" unrestrained with a temperature swing of 100-150 degrees F (can't remember what I used years ago when I calc'ed this). That means there would have to be enough slack in the chain for it to increase it's length by 1/8" (1/16" up and back down). So imagine it's 0 degrees on a cold morning, the chain has worn into that aluminum lower sprocket a little, and that auto tensioner gets one more click tighter that it was on the edge about before. Now fire the sled up and start riding, deep snow starts covering over the hood vents, underhood temps rise, chaincase starts expanding, aluminum lower gear starts expanding, and you hit the other side of a creek crossing with the track under full load with a fiddle-string tight chain...

Now the numbers are probably a little different here and there, but that's the concept. This also demonstrates why you have to leave a belt drive belt loose, and it gets tighter after everything heats up. Cat's fix after 2015 was to put a stronger chain in that doesn't break as easy. It seems to work, but doesn't really address the root problem.

I thought the use of magnesium was pretty trick. Man that stuff is light. I pulled the stock 17MC oil tank/chaincase cover off and replaced it with a billet aluminum cover and a way smaller aluminum tank (nice piece) from skinz. besides less oil in the tank, there was no weight savings to be had there. I like that i will now get some under hood heat flowing out that side tho. the stock setup is a huge heat blocker. I questioned the use of the aluminum driveshafts when those came out, and they seem to be holding up good. The expansions of different metals is a thing, i have a hard time believing its a problem when you look at the number of units on the snow without issue

 

[boondocker97]

They are light for sure! When my 2014 let go in Togwotee I went into the rental shop looking for parts and they were having some issues with their rental units as well at the time. I don't think it was ever a pandemic level problem, but enough that Cat changed it for 2016+. The Ascender sleds seem to have proven to be adequate with that new chain setup.

The expansion thing I was talking about was just a possible explanation I came up with as to why there seemed to be more failures 2012-2015 than what we had seen in the past with aluminum cases.

 

[Dam Dave]

aluminum sprockets are available for just about every high power motorcycle, yes they wear faster than steel sprockets, but that is in a open chain situation, in the oil bath of a chain case they will last a long time, yes the oil will have aluminum specs in it

I have never seen a photo of a failed Cat aluminum bottom gear? I personally rode out of the backcountry with a empty chain case when a rock poked a hole in the outer case, it wasn't even hot when I got to the truck

 

[chas6663]

The auto tensioners break, I put manual one's in

 

[JMCX]

I was doing a routine inspection and found the tensioner all askew. The pivot had snapped off. Not sure how long it was like this. 7000km on the sled. Previous year l hit a rock and broke the bottom. Fixed that with JB weld. Dealer says the uneven wear on the shoe is typical. I got creative with a fix for the pivot.

 

[boondocker97]

Nice fix! I probably would have gone manual at that point though.

 

[JMCX]

Nice fix! I probably would have gone manual at that point though.

I thought about that. Does the manual adjuster not use the same pivot?

 

[boondocker97]

I thought there was an option that didn't need it but thinking a little harder I believe you're right. They all still need that peg.

 

[madmax]

Manual uses the pivot