Doubler shift question

[Magikal]

Good information. Keep it coming

 

[Bent77]

Early stuff was typically a re-splined factory shaft and the better ones were re-heat treated. Our earliest versions were available with 10 spline and 27 spline intermediate shafts. You had to be particularly careful with those. Shortly after that we went to a 32 spline shaft only and they're pretty tough but it's still possible to break it by running with the 205 in high and 203 in low. This is actually the reason behind the Magnum, in that system we could make the shaft big enough that you can use it any way you want. With the 203 it's easy enough to run it right because there's really nothing to gain by doing it wrong since the gear ratios are so close together.

For a deeper dive into this: The reason the intermediate shaft becomes weak when the 203 is in low is that in that situation you have one 32 spline shaft going into the 205 and two 32 spline shafts coming out. If we say a 32 spline shaft has 4000ft-lb of torque capacity then we have 8000ft-lb of output capacity but only 4000 coming in. In that situation the outputs can be loaded to only half their strength and the input will snap. If the 205 is in low, you have the same two output shafts but also have a 2:1 gear reduction before them. So now the 4000ft-lb capacity coming in turns into 8000ft-lb going out and both outputs are at their breaking point before you snap the input. Chances are the outputs won't be loaded equally so you tend to snap an output before breaking the intermediate. And with that much torque on tap the real story is that you generally break axle parts before you have T-case problems.

Basically, we shift the 205 into low about the time we hit dirt and toggle the 203 in and out of low gear depending on the terrain.

Thanks @Stephen

 

[muddermilitia]

Early stuff was typically a re-splined factory shaft and the better ones were re-heat treated. Our earliest versions were available with 10 spline and 27 spline intermediate shafts. You had to be particularly careful with those. Shortly after that we went to a 32 spline shaft only and they're pretty tough but it's still possible to break it by running with the 205 in high and 203 in low. This is actually the reason behind the Magnum, in that system we could make the shaft big enough that you can use it any way you want. With the 203 it's easy enough to run it right because there's really nothing to gain by doing it wrong since the gear ratios are so close together.

For a deeper dive into this: The reason the intermediate shaft becomes weak when the 203 is in low is that in that situation you have one 32 spline shaft going into the 205 and two 32 spline shafts coming out. If we say a 32 spline shaft has 4000ft-lb of torque capacity then we have 8000ft-lb of output capacity but only 4000 coming in. In that situation the outputs can be loaded to only half their strength and the input will snap. If the 205 is in low, you have the same two output shafts but also have a 2:1 gear reduction before them. So now the 4000ft-lb capacity coming in turns into 8000ft-lb going out and both outputs are at their breaking point before you snap the input. Chances are the outputs won't be loaded equally so you tend to snap an output before breaking the intermediate. And with that much torque on tap the real story is that you generally break axle parts before you have T-case problems.

Basically, we shift the 205 into low about the time we hit dirt and toggle the 203 in and out of low gear depending on the terrain.

Thanks for the clarification.

The other thing to consider is that the 205 is more difficult to shift in and out of gear than the 203 is. So it is a good idea to put the 205 in low ahead of time. Then when you get to the difficult stuff, it's easy to shift the 203 as needed

 

[Magikal]

I tried this concept a few days ago while out wheeling and, yes, the 203 is much easier to shift in and out. Gonna have to rearrange my levers i think.

 

[tarussell]

Early stuff was typically a re-splined factory shaft and the better ones were re-heat treated. Our earliest versions were available with 10 spline and 27 spline intermediate shafts. You had to be particularly careful with those. Shortly after that we went to a 32 spline shaft only and they're pretty tough but it's still possible to break it by running with the 205 in high and 203 in low. This is actually the reason behind the Magnum, in that system we could make the shaft big enough that you can use it any way you want. With the 203 it's easy enough to run it right because there's really nothing to gain by doing it wrong since the gear ratios are so close together.

For a deeper dive into this: The reason the intermediate shaft becomes weak when the 203 is in low is that in that situation you have one 32 spline shaft going into the 205 and two 32 spline shafts coming out. If we say a 32 spline shaft has 4000ft-lb of torque capacity then we have 8000ft-lb of output capacity but only 4000 coming in. In that situation the outputs can be loaded to only half their strength and the input will snap. If the 205 is in low, you have the same two output shafts but also have a 2:1 gear reduction before them. So now the 4000ft-lb capacity coming in turns into 8000ft-lb going out and both outputs are at their breaking point before you snap the input. Chances are the outputs won't be loaded equally so you tend to snap an output before breaking the intermediate. And with that much torque on tap the real story is that you generally break axle parts before you have T-case problems.

Basically, we shift the 205 into low about the time we hit dirt and toggle the 203 in and out of low gear depending on the terrain.

Damn, that is an excellent yet basic and simple explanation !

I have explained about why the input of a second gear box in high range ( with the forward range box in reduction mode ) is potentially a bad combo many times but never with such few words and that clearly - great explanation and simple too !

 

[kennyw]

Damn, that is an excellent yet basic and simple explanation !

I have explained about why the input of a second gear box in high range ( with the forward range box in reduction mode ) is potentially a bad combo many times but never with such few words and that clearly - great explanation and simple too !

Shaft go boom isn't simple enough?

 

[SnackPack]

remember, if you modified the shift detents...be careful not to cross up the transfer case shifters (IE front in LO, rear in HI)...just like in ghost busters...crossing the streams is bad

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it's true. That's how you get this: