Need help understanding clutch, spur and gear ratios....

[override]

So I found the gear ratio sticky on here but I'm not quite sure I follow it....I have also found many other useful bits of information but none of them exactly explain how these numbers work with each other, and how it changes your final ratio....Etc. Etc.

I have read that the T-Maxx pitch is 32 and that the stock gear ratio is 2.85:1 and stock clutch/spur is 22/72.

Now all that above is Chinese to me as I don't understand Gear Ratios at all.

I read that 23/65 will give you the same ratio of the stock maxx when using the UE 7.5 diffs. A guy on Beat your truck forums said he runs 18/38 with mod 1, whatever mod 1 means I dont know.

Any one out there who can sit down and explain all this crap to me?

Ultimatley I just want to understand how it all works so I can do my own setups, but I also will be upgrading my truck soon and dont want to go through trial and error and money to figure out what works.

My truck will have a Picco .26 Red Dot and 1/8th diffs....

 

[Racer 1966]

Simplified it's like this, divide your tooth count of your spur gear by the tooth count of the clutch bell to get the ratio. With the ratio,numerically higher numbers are lower gearing or in other words will give you more usable power at low speeds and make your top speed slower. Lower numerical ratio numbers will give you more top speed while making the engine work harder to accelerate from a stop or in other words it will seem sluggish at low speeds.

Keep in mind that when changing ratios,a little can be a lot. You have to have gearing that works in the power range of your engine. At first it's best to talk to others that have the same set up to get an idea for your best gearing.

Lastly, the 32 pitch and mod 1 refer to the design of the gear itself and has nothing to do with ratios.

 

[override]

Simplified it's like this, divide your tooth count of your spur gear by the tooth count of the clutch bell to get the ratio. With the ratio,numerically higher numbers are lower gearing or in other words will give you more usable power at low speeds and make your top speed slower. Lower numerical ratio numbers will give you more top speed while making the engine work harder to accelerate from a stop or in other words it will seem sluggish at low speeds.

Keep in mind that when changing ratios,a little can be a lot. You have to have gearing that works in the power range of your engine. At first it's best to talk to others that have the same set up to get an idea for your best gearing.

Lastly, the 32 pitch and mod 1 refer to the design of the gear itself and has nothing to do with ratios.

Thanks for the information...That helps more than you know!

The biggest thing I don't understand is if your actual diff ratio is 2.85:1 or 3.31:1 or whatever the size may be..In this case 3.31:1, does changing your clutch/spur T size actually change your final 3.31 ratio?

I would think that it would stay the same regardless of what your clutch/spur was changed to. Meaning you would actually have two ratios to work with, correct?

So when looking at these charts that are on the net, they have your clutch/spur ratio and then what gear ratio those two combined create. Is it a good starting point to match that ratio with your diff ratio to get a balanced beginning point?

Am I even getting close here?

 

[override]

Anyone wanna chime in on my last post?

 

[Racer 1966]

The clutch/spur combo changes the input speed of the trans shaft. The only change for the final drive ratio is to change tire size or mod it to use a different diff.

IMO,the best place to start is to look at the stock numbers. Then adjust by just a couple of teeth on either the clutchbell or spur move the power in the direction you want improved. More teeth on the bell for higher top speed or more teeth on the spur for better low end acceleration.

 

[k5floyd]

You are getting close. Changing you spur/clutch bell ratio will not change the gear ratio in you diffs but it will change your final drive ratio. Final drive ratio is all of your gear ratios multiplied together, clutch/spur ratio times transmission ratio times diff ratio. So gearing down (numerically higher) in you diffs will affect your final drive ratio making it numerically higher which is why you might want to compensate by gearing up (numerically lower) with the clutch/spur gears.

 

[override]

Awesome! Again thanks for the useful information! This is all starting to make much more sense to me.

Ok, so k5floyd, with your input on the final drive ratio...I'm going to take a wild guess and say the way you figure your transmission ratio is by taking your top shaft gear and your 1st gear tooth count and divide for your low end ratio and your top shaft and 2nd gear for your high end ratio?

Seems like this covers the basics and should get me moving along when I start gearing my truck for the new motor and diffs.

 

[k5floyd]

sounds like you are correct. I'm not completely sure what each gear in the trans is called tho. to calculate gear ratio you would divide the number of teeth on the driven gear(the gear being driven) by the drive gear(gear doing the driving). in the case of the clutch/spur gears you would divide the spur gear by the clutch bell. in the case of the differential you would divide the ring gear by the pinion gear.