Gearing math

[Violent violet 0]

Does anybody have the math behind the gear ratios in a wheel horse.  I have a 8 speed trans axle currently running a 5.25 front pulley and 6.375 rear pulley.   I use the tractor for garden tractor pulls. This setup gives me a cubs equivalent of a 27t third gear which performs very well on a hard low traction track.  But on a track with lots of bite I run second however that’s a 21t equivalent and a little too fast of a gear to get good mph.   I’m wondering if there’s a calculation I can use to determine if I can utilize low range third and if so what gear that would be after the pulley swap. 

[rmaynard 15,580]

Wow. Math is not my subject. However, I have found that when it comes to pulling info (and I don't pull) this website has the most information, not only on pulling, but engine rebuilding and more. 

 

http://gardentractorpullingtips.com/transaxl.htm

 

 

[953 nut 55,734]

Our resident gear guru @stevasaurus may have the ratio numbers you are seeking. I couldn't find any ratio information but did find ground speed info for a stock Wheel Horse.

[ebinmaine 68,205]

Here's a chart I tripped over a few years ago and saved. 

I believe this goes back to the days of SIX SPEEDS but an 8 should be similar or identical.  

 

Two orientations because one may be easier to read than the other.  

 

 

[ebinmaine 68,205]

Note that Low Range is approximately a division of 4 from High.  

[Achto 27,742]

1 hour ago, Violent violet said:

I’m wondering if there’s a calculation I can use to determine if I can utilize low range third and if so what gear that would be after the pulley swap. 

 

I think that you would be better off finding a happy medium in high range. Note: 3rd gear low is a lower gear than 1st gear high.

Edited December 16, 2023 by Achto

[pfrederi 17,856]

6/8 spd same ratios

[Jon Paulsen 290]

Most of the owners manuals I've looked at have a speed chart, gear by gear. If you don't have a manual, search here by model number: https://www.wheelhorseforum.com/files/ Adding "OM" to the search should help narrow it down. OM = Owners Manual, "IPL" is for the parts manual (great exploded views), and SM is for Service Manuals. There's a ton of information available. 

[stevasaurus 22,841]

Not exactly sure what to say here.  As far as I know...all of the Wheel Horse manual transmission gear ratios are basically the same.  That means all 3, 4, 6 high, & 8 high ratios are equal.  The things that can make a difference in speed and torque, are tire size and air presure, drive pulley size and input pulley size on the tranmission.  I believe @wallfish may be of more help with tires and pulley sizes to do what you want to do.

   I'm wondering if I would be correct in saying...any STOCK from the factory (Manual trans) Wheel Horse at a given RPM would run the same speed as any other Wheel Horse.  

                                       

[wallfish 17,078]

By using the gear ratios posted above and a pulley size calculator like this one,

https://www.blocklayer.com/pulley-belteng

You can mathematically figure out what you want.

There are plenty of calculators online to convert the axle rpm into ground speed. Tire diameter is a big variable and different size tires can be used to adjust the ground speed.

RPM of the particular engine is another variable you will need to know and it's also a way to "adjust". Torque ratings for the different rpm can be found by using the engine model so staying in the top torque range is probably best. Any modifications to the engine is another variable to consider. 

As Achto pointed out, low range is LOW and probably not what should be used.

Changing tires to a smaller size diameter for the different track and maybe some minor RPM adjustment could be enough and the easiest way but IDK

[8ntruck 7,079]

Final gearing can be easily adjusted with tire diameters or changing engine and transmission pullies. 

 

Smaller tire diameter will act like a lower gear.  A larger tire will act like a higher gear.  If you think you want something between 2 high and 3 high, you have a couple of choices.  You could run in 3 high with smaller diameter tires, or run in 2 high with larger diameter tires.

 

2 ply tires will act differently than 4 ply tires.  The more plies in a tire, the stiffer the sidewall will be.  Stiffer sidewalls make the rolling radius less sensitive to tire pressure changes.  Stiffer sidewalls will make the tire less likely to mold the tread contact patch to the ground.

 

Using a larger engine pulley will act like a higher gear.  Using a smaller transmission pulley will also act like a higher gear.  Going the other way, with a smaller engine pulley and/or a larger transmission pulley will act like a lower gear.

 

Changing pulley diameters might require a different drive belt. Changing pulley diameters will also change the position of the belt relative to the belt guides on the belt guard.  Adjustments might be needed in the belt guides to get a good clutch action.

 

If you keep the sum of the engine pulley diameter and the transmission pulley diameter the same when you make a change, you should be able to use the same drive belt. 

 

Good luck.

 

[Handy Don 12,436]

The only published difference in drive ratios that I’m aware of was with the “-C” and “-HC” models aimed at commercial users. These had taller final gearing for more speed.

The “tall tire” tractors (e.g. GT14, C-195) had the potential for more speed due to the larger diameter tires, as @8ntruck noted.

Edited December 17, 2023 by Handy Don

[953 nut 55,734]

4 hours ago, Handy Don said:

The “tall tire” tractors (e.g. GT14, C-195) had the potential for more speed due to the larger diameter tires

The GT-14 has a larger output gear on the Sundstrand than would be found on the Charge/Electro and a slightly smaller input gear in the transaxle to compensate for the larger tire size. If I remember correctly the GT-14 Sundstrand had 13 teeth on the output compared to 10 on the Charger/Electro.

[Handy Don 12,436]

2 minutes ago, 953 nut said:

GT-14 has a larger output gear on the Sundstrand than would be found on the Charge/Electro

Speedup thwarted!