Drive shaft pitch change

[THEPASMAN]

Quick question
2018 mtx has 3” pitch drivers what gearing change would be required if a guy was to change drive shaft to a 2.86 ?

Track needs replacing and I want to go to a 2 1/2 “ and don’t like options in the 3” pitch tracks

Is this as easy as just changing shaft and gears or is there more to it

 

[justinator]

If you went to a 9 tooth 2.86 pitch shaft instead of your 3.0- 8 tooth you would have to gear down by approx 6.8% to retain the same drive ratio you currently have.

 

[Fleecer]

What do you have for current gears top/bottom?

 

[74Nitro]

I had a 18 xtx, but not the btx. It came with 21/41. I recall the speedo read much higher than the GPS was reading.

 

[sideshowBob]

I have a 2019 X-TX LE with 8 x 3" track drivers and came stock with 21/41 gears

The 2019 SRX LE has 9 x 2.86" track drivers and also came stock with 21/41 gears

Therefore the SRXs were geared @ 7% higher then the X-TXs because of track driver differences. Because of this I geared my X-TX to 21/37

The interesting thing about all this is that the Speedo trigger/magnets at the end of the driveshafts are identical on both sled models and probably the MTX and BTX as well.

I doubt YamaCat calibrated the ECUs differently for speedo accuracy between the models as my X-TX definately over indicates in comparison to GPS and I have heard the SRX speedos are fairly accurate.

Even though my X-TX speedo reads high its no where near as bad as the 850 Renegades in our group and way better then my Attak speedo was before I removed two teeth off the speedo trigger gear.

 

[lakercr]

There are 8 magnets on the end of the driveshaft that the pickup sees for determining speed. On a stock winder with 2.86 pitch 9T that is an effective wheel size of 25.74" (2.86 x 9 = 25.74). An 8T driver with 3.0 pitch is 24", which is about 7% smaller circumference, so it will read higher. The radius of the driveshaft and its relation to the pickup don't change with different drivers, just the rollout (effective circumference). No different that on a truck with larger tires - your actual speed will be higher than indicated. If you put smaller tires on your truck, your actual speed would be less than indicated.

 

[sideshowBob]

There are 8 magnets on the end of the driveshaft that the pickup sees for determining speed. On a stock winder with 2.86 pitch 9T that is an effective wheel size of 25.74" (2.86 x 9 = 25.74). An 8T driver with 3.0 pitch is 24", which is about 7% smaller circumference, so it will read higher. The radius of the driveshaft and its relation to the pickup don't change with different drivers, just the rollout (effective circumference). No different that on a truck with larger tires - your actual speed will be higher than indicated. If you put smaller tires on your truck, your actual speed would be less than indicated.

Yes my point...and as I said Yamacat did not calibrate the ECU in different models for variances in driver size hence the inaccurate speedos on some models.

 

[Fleecer]

Quick question
2018 mtx has 3” pitch drivers what gearing change would be required if a guy was to change drive shaft to a 2.86 ?

Track needs replacing and I want to go to a 2 1/2 “ and don’t like options in the 3” pitch tracks

Is this as easy as just changing shaft and gears or is there more to it

Yes, just a matter of changing drive shaft/gears/track. Stock gears in 2018 MTX are 21/49, which with an 8T 3.0 pitch driveshaft brings a top speed of 87.6 mph.

To match the same top speed while changing to a 2.86T 9T driveshaft, you will need 20/50 gears, which will yield 87.75mph. These gears will require a 90p chain.

Hope this helps!!

 

[THEPASMAN]

Thanks Fleecer
That the answer I was looking for

what would be the downside of not putting in gears and running the stock one. 7% increase would be about 103.5 mph still pretty low or is it a decrease

 

[sideshowBob]

If you are doing more flat land running and not doing mega vertical high altitude climbs I think leaving the stock gearing would work pretty good.

 

[THEPASMAN]

Thanks
It will be mostly flatland and it’s got a new upper gear so I’m probably going to leave it

thanks for all the reply

 

[THEPASMAN]

The Speedo will be what it will be

 

[sideshowBob]

The Speedo will be what it will be

It will be way more accurate with the 9 x 2.86 drivers.

 

[Yamajon1]

In the Viper models the ECU programming does contain calibration with driver size info for speedometer. When dealers were doing ECU reprogramming for starting issues a few years back some sleds were being reprogrammed incorrectly and the result was speedometer error. Not saying the Winder is the same set up but they are both Yamacats?

 

[THEPASMAN]

Would track length have to be changed to a 154 with the 2.86 drivers