Suzuki rear differential

[ChuckChapman]

I have recovered a Suzuki king quad atv rolling chassis. No plastics, engine fuel tank etc.
it does however have steering, suspension, front and rear differentials and there is a braking system built into the rear differential. It’s roughly 3.75 to 1 ratio. Input shaft turns 3.75 for every tire revolution. Is it possible to run a cvt clutch and a drive shaft to the differential? Or turn it 90* and put a sprocket or pulley in its place?

 

[ezcome-ezgo]

Here's the thing about asking "is it possible...", the answer is almost always: yes. There are other constraints however. Is it practical? What skills are required to achieve the desired outcome? Would the fabrication time and parts needed to make it work be move expensive than the traditional components of a live axle?

What direction does the differential input need to turn? If you are thinking about driving this with an industrial engine, this is an obvious 1st question.

 

[ChuckChapman]

14hp single cylinder Koehler. So I don’t think this would have high rpms. I can keep all the original mounting brackets for the A arms and suspension and hopefully just lengthen the axles between the cv joints. Just wasn’t sure how to get to the proper ratios from my clutch or how to get it to a shaft drive system.

 

[mckutzy]

Can we see some pics of the stuff you have to start with ... Motor, rear end ect.. you plan to use..

 

[ChuckChapman]

I will as soon as I can figure out how ��

 

[anderkart]

I will as soon as I can figure out how ��

This link has good info about posting pics: http://www.diygokarts.com/vb/showthread.php?t=737

 

[ChuckChapman]

Here you go,
Chuck

 

[ezcome-ezgo]

I would salvage as much of the supporting framework and fab/place the engine such that it's rotation turns the dif in the right direction. The ratios are just math; I'd guess you want to underdrive the motor to diff to around 4:1. << disclaimer: I could be wrong >>

 

[ChuckChapman]

I just received my CVT clutch and going to start mocking things together this weekend. Debating on trying to run a solid shaft through to both diff’s and making it 4x4. The electric switch is still attached and the wiring is still there. Wondering if I can just put a shaft through my bottom cvt pulley and attach to both diffs? Would it be gear reduced far enough?

 

[ChuckChapman]

Put the cut off wheel to work cutting away unnecessary tubes, brackets and atv junk starting tacking the frame together and measuring for engine placement. Gonna have to extend it further than I anticipated with double checking engine rotation and finding it turns opposite of what I wanted. Still trying to run the numbers on if it’s possible to skip a jack shaft and mount the clutch/pulley directly to the rear differential.

 

[anickode]

Put the cut off wheel to work cutting away unnecessary tubes, brackets and atv junk starting tacking the frame together and measuring for engine placement. Gonna have to extend it further than I anticipated with double checking engine rotation and finding it turns opposite of what I wanted. Still trying to run the numbers on if it’s possible to skip a jack shaft and mount the clutch/pulley directly to the rear differential.

Just flip it upside-down. Top is bottom and backwards is forwards.

 

[ChuckChapman]

Turned it backwards last night. Trying to fit the engine in and around the rear suspension and differential. I’ll need a longer belt due to fitting issues. Next is figuring out how to attach the bottom pulley to the front of the rear deferential. With spinning the rear end around I won’t be able to have it 4x4. Keeping both front and rear differentials because they contain the braking systems. Gonna try skipping a jack shaft and hoping that the differential has a low enough reduction for a direct belt drive. What is the calculation to figure out final reduction?

 

[bob58o]

You just multiple all the reductions.
If by CVT, you mean 30 series Torque Converter with 6" Driven unit - that has a 0.9 :1 final ratio.

If you have 3.75 :1 from the differential then ...

3.75 * 0.90 = 3.375 :1

The CVT in low gear has a 2.68 :1 Ratio.

3.75 * 2.68 = 10.05 :1

If a 40 series, then...

3.75 * 1 = 3.75 :1 in High
3.75 * 2.43 = 9.11 :1 in Low

 

[anickode]

Turned it backwards last night. Trying to fit the engine in and around the rear suspension and differential. I’ll need a longer belt due to fitting issues. Next is figuring out how to attach the bottom pulley to the front of the rear deferential. With spinning the rear end around I won’t be able to have it 4x4. Keeping both front and rear differentials because they contain the braking systems. Gonna try skipping a jack shaft and hoping that the differential has a low enough reduction for a direct belt drive. What is the calculation to figure out final reduction?

mount the diffs upside down. It will solve your direction problem without having to change your whole design. You can drill and tap new drain plugs and vents.

 

[ChuckChapman]

So I have a 40 series and by your math I should be able to connect directly to the differential. Correct?

---------- Post added at 07:11 PM ---------- Previous post was at 07:09 PM ----------

I’m not sure if my differentials are able to be flipped with all the suspension and brake mounts. If I want to keep the 4x4 idea I can extend the differential output shaft to a set of sprockets and a drive shaft to the front differential.

 

[bob58o]

So I have a 40 series and by your math I should be able to connect directly to the differential. Correct?

How tall are your tires?

Assuming 20" diameter tires, 3600 RPM, 3.75 :1 Gear Ratio...
57mph.

IMHO, I think it is geared too fast. I would want more low end, but I'm just guessing on tire size.

I'd like another 1.5 :1 Reduction in there.... Giving 14:1 in low and 5.6 :1 in High.

My buggy with 18.5" tires and 420cc engine has a 40 series and 60T :11T sprocket ratio. 5.45 :1 Final Ratio. 50 MPH at 5000 RPM.

 

[ChuckChapman]

AT 25x10-12 rear tire size.

 

[bob58o]

AT 25x10-12 rear tire size.

25" Tires? WOW!

No I do not think you can go with that set up.s
With 25" Tires, me thinks 7.5 :1 final reduction is closer to what you want than 3.75 :1.

3.75 :1 final reduction gives 71mph at 3600 RPM.
The CVT is never going to fully shift.

And 7.5 :1 obviously gives half that (~36mph).
6 :1 = 45mph at 3600 RPM
5 :1 = 53mph at 3600 RPM

Will the differential take 40 lb-ft of torque input? 80 lb-ft?

 

[ChuckChapman]

I would think it’d take quite a bit of torque. Had 750cc engine when it started life. It will be geared lower for now with my kids doing most the driving. Rather have torque for the mud than top speed. Gonna leave room on the jack shaft for a future 2 speed upgrade.

---------- Post added at 02:27 PM ---------- Previous post was at 02:21 PM ----------

Correct me if I’m wrong to get to a 7.5:1 ratio a ten tooth on the clutch shaft to a 75 tooth going into the differential?

 

[bob58o]

I would think it’d take quite a bit of torque. Had 750cc engine when it started life. It will be geared lower for now with my kids doing most the driving. Rather have torque for the mud than top speed. Gonna leave room on the jack shaft for a future 2 speed upgrade.

---------- Post added at 02:27 PM ---------- Previous post was at 02:21 PM ----------

Correct me if I’m wrong to get to a 7.5:1 ratio a ten tooth on the clutch shaft to a 75 tooth going into the differential?

If you wanted a 7.5 :1 final Reduction, the CVT gives 1:1 in high gear, and are getting 3.75 :1 from the differential...
Then you would need something like the Driver unit on the crankshaft. The driven unit and a 10T sprocket on the jackshaft, and a 20T sprocket on the differential input shaft.

2.43 * 2.0 * 3.75 = 18.2 :1 in low gear
1.0 * 2.0 * 3.75 = 7.5 :1 in high gear