Gear down 850 RMK

[Nolimits]

I have 2023 850 Pro RMK non Slash 2.6 track. It has the stock gearing 22-43. Has anyone put the 50t bottom gear and belt on from the 2.75 track models? It would give you a 2.27 ratio vs the 1.95 stock ratio. I know the driveshafts are different part #'s from the 2.6 vs 2.75. Are the inner splines the same?

 

[sledhed]

I have 2023 850 Pro RMK non Slash 2.6 track. It has the stock gearing 22-43. Has anyone put the 50t bottom gear and belt on from the 2.75 track models? It would give you a 2.27 ratio vs the 1.95 stock ratio. I know the driveshafts are different part #'s from the 2.6 vs 2.75. Are the inner splines the same?

QD to QD2 should be totally doable. Splines should be the same all years basically... driveshafts are different part# due to 2.86 vs. 3.5 pitch drivers as they sell as a unit I believe. I would give the QD2 a mixed review personally, depends on where you ride and snow conditions, the 850 is such a torquey motor that having a little higher ratio seems to work well with that motor especially with a 2.6" track...

 

[Nolimits]

I forgot to mention it is 155. I ride the sled at home in MN if our whole family rides, if not I ride something else. I have ridden West Yellowstone / Island Park 14 years including 9 in a row. We have encountered every condition possible I think from rain to feet of fresh powder. We were out there last weekend and had the most fresh powder I have ever seen out there. We ride meadows, trees and small climbs. We are not highmarkers or racers. I have always liked a geared down sled and this seemed like an easy way to do it.

 

[Teth-Air]

I always gear down my Polaris sleds. 23 850 NA with 165 series 8 and 24 Boost with 165 series 9 track. The 850 is torquey but is soft on the bottom. Gearing down makes them easily get into the power band. Both are geared down with 25:63 gear sets from TKI. That is about 10% lower than the QD2. My NA will run side by side with the 9R in a race. I also have done clutching to take advantage of the gearing.

 

[Nolimits]

I will have to do some clutching as I was only running about 8050-8150. This was my first trip out west with it and is stock clutching. Now I have a baseline for next year. What RPM’s is everyone running?

 

[Ultrasauras]

Our works the best at 8300

 

[newfrank]

I always gear down my Polaris sleds. 23 850 NA with 165 series 8 and 24 Boost with 165 series 9 track. The 850 is torquey but is soft on the bottom. Gearing down makes them easily get into the power band. Both are geared down with 25:63 gear sets from TKI. That is about 10% lower than the QD2. My NA will run side by side with the 9R in a race. I also have done clutching to take advantage of the gearing.

This goes to a 2.52 ratio with 25/63 gearing. Does this setup allow you to run the same stock belt? Stock ratio is 2.27 with 22/50 gearing. Increasing the ratio to 2.52 from the stock 2.27 would be gearing up, or do I have it backwards?

What's the benefit of kurts kit (2.37 ratio with 32 top and 67 bottom)? I think this is also gearing up.

I'm not trying to start anything, just trying to learn here. If I can squeeze more out of my 850 with gearing then I'm all for it, whatever works.

 

[live2beel]

25/63 is a TKI belt drive.

 

[Scott]

Kurt's Polaris Gear Down is in between QD1 and QD2.

So if you have have a QD1, Kurt's would be a gear down.
If you have a QD2, Kurt's is a gear up!

It's what they felt is the optimal gear ratio. I can't disagree with him at all. I sure am happy with my 25 Khaos 9R, Kurt's clutching and Kurt's GearUp.

 

[PSI 800]

I have the same kurts set up and love it

 

[Fat_Tones]

Kurt's Polaris Gear Down is in between QD1 and QD2.

So if you have have a QD1, Kurt's would be a gear down.
If you have a QD2, Kurt's is a gear up!

It's what they felt is the optimal gear ratio. I can't disagree with him at all. I sure am happy with my 25 Khaos 9R, Kurt's clutching and Kurt's GearUp.

I think this used to be the case but not anymore. Current Kurt's is 29/69 (2.38) and QD2 22/50 (2.27).

 

[Scott]

I think this used to be the case but not anymore. Current Kurt's is 29/69 (2.38) and QD2 22/50 (2.27).

Well it's straight from Curt, so I'm not sure what to tell you.

 

[Fat_Tones]

Well it's straight from Curt, so I'm not sure what to tell you.

You communicated directly with Kurt's and they stated their kit (KO3267) is geared up from QD2?

 

[Fat_Tones]

Well it's straight from Curt, so I'm not sure what to tell you.

Ok nevermind I see now......there's a kit KO3267 which is 32/67 sprockets (2.09) which would be in between QD1 and QD2, and there's a kit KO2969 with 29/69 sprockets (2.38) which would be a geardown from QD2. Sorry about the confusion.

You communicated directly with Kurt's and they stated their kit (KO3267) is geared up from QD2?

 

[Teth-Air]

This goes to a 2.52 ratio with 25/63 gearing. Does this setup allow you to run the same stock belt? Stock ratio is 2.27 with 22/50 gearing. Increasing the ratio to 2.52 from the stock 2.27 would be gearing up, or do I have it backwards?

What's the benefit of kurts kit (2.37 ratio with 32 top and 67 bottom)? I think this is also gearing up.

I'm not trying to start anything, just trying to learn here. If I can squeeze more out of my 850 with gearing then I'm all for it, whatever works.

Not stock belt. The TKI has a tensioner. The tensioner allows multple gearing choices but it does much more than that. As the tensioner pushes in, the belt is forced to wrap 3/4 the around the top gear. This makes for much more teeth contacting than the stock set up. When there is more contact a smaller top gear is adequate without slipping or stripping the belt. Now the top gear is smaller, a smaller lower gear is also possible without compromising ratio. this smaller bottom gear helps avoid contact with the belly pan. I have seen several broken lower gears and going larger on the lower is worse for clearance.

Keep in mind Doo and Cat traditionally run 2.5:1 or even lower gearing(higher ratio) and why do you think they chose that when Polaris went with 2.27? Polaris has been limited due to physical size and no tensioner. But you can see the trend has been toward lower gearing over the past couple years. For those gearing up I will argue all day that there is zero advantages for mountain riding. Now that Polaris uses the P22 clutch that is wider around the center bearing, these sleds start out in a higher gear than the P85. This is a huge disadvantage, especially for the turbos that lack bottom end compared to the NA's.

 

[newfrank]

Not stock belt. The TKI has a tensioner. The tensioner allows multple gearing choices but it does much more than that. As the tensioner pushes in, the belt is forced to wrap 3/4 the around the top gear. This makes for much more teeth contacting than the stock set up. When there is more contact a smaller top gear is adequate without slipping or stripping the belt. Now the top gear is smaller, a smaller lower gear is also possible without compromising ratio. this smaller bottom gear helps avoid contact with the belly pan. I have seen several broken lower gears and going larger on the lower is worse for clearance.

Keep in mind Doo and Cat traditionally run 2.5:1 or even lower gearing(higher ratio) and why do you think they chose that when Polaris went with 2.27? Polaris has been limited due to physical size and no tensioner. But you can see the trend has been toward lower gearing over the past couple years. For those gearing up I will argue all day that there is zero advantages for mountain riding. Now that Polaris uses the P22 clutch that is wider around the center bearing, these sleds start out in a higher gear than the P85. This is a huge disadvantage, especially for the turbos that lack bottom end compared to the NA's.

Okay that all makes sense then! I've got SRP clutching in my 850 and that was a big improvement over stock. A gear down sounds like the next step!

What is the kit from TKI you are using for your NA's?

https://tkicnc.com/product/2016-2019-polaris-axys-2-6-belt-drive/ is all I can find and lowest gear is 26T. The drop down only goes down to 26T but product specs says 25T is lowest, so maybe just an error on the website.
You are running 25/63 from TKI?

 

[Pickin’ Boogers]

I’ve run the 25t, 26t, and 27t top gears on the TKI and it’s one of the mods I almost always do. Really helps with technical tree riding and I don’t care about top speed racing across lakes. The 25t doesn’t show in the drop down menu but it’s available.

 

[jowzi]

I also wondered about the gear-down of the 850 RMK. Switching to the 50T at the bottom could really improve the torque and responsiveness, especially in deep snow. But as you say, the trees are different between the 2.6 and 2.75. To see if the internal splines are compatible, otherwise it may be more complicated. If anyone has tried the experiment, I would be curious to get feedback!

Tutuapp​

 

[NapaMatt]

I have used both set ups. 22/43 and 22/50 With the 50 the na bottom is more rippy. Faster throttle response for sure. Just note when using the 50 pay attention to ice chucks. or wood or exh springs getting jammed in-between the plastics.

 

[Nolimits]

I have only looked at pictures of the gears and both QD1 and QD2 have the same number of inner splines. I am 98% sure I’m going to order the QD2 lower gear and belt. I can always return if they do not fit.