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Really dumb question related to turning back wheel and drive shaft

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M

MGNoir

Jedi Hopeful
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I've had my Midget up on jack stands now for several months as I've been cleaning out the engine bay, repainting some things, rebuilding front suspension, etc. Wheels are off.

Today I was going to reset the timing and reinstall the distributor. So I put it in gear (4th), and went back and turned the rear axle via the brake drum to get it to the valves to the right spot. Except when I turn it, it just spins free - no rotation of the drive shaft. Same on both sides.

Isn't... (and this is where I'm feeling like I'm totally missing something)... isn't the drive shaft supposed to turn when I rotate the rear wheels?

PS
I should add that this car was drive-able before it sat idle. Nothing broken in the drive shaft.

PPS
For some time, I had it on jack stands on two sides of the axle housing, but just had moved it to the attachment point of the front of the leaf springs. Could this have stressed out the axle and caused something to snap?
 
Like most cars, this car has an "open" differential.

When you put the car in gear, have both wheels off the ground and turn one rear wheel, the other rear wheel will turn backwards. This is normal and is a function of the open differential.


For more info, slide to about 3:00 in ~This Video~
 
OK, so... what you're saying is when BOTH are free to spin, and one gets turned, the other turns the opposite to compensate as it were for differences - and as a result, there's no prop shaft rotation? And if one wheel isn't allowed to spin, then turning the other will turn the prop shaft?

*edit* I attached one of the wheels and now I can see the rotation of the opposite side. W/o wheels attached I wasn't seening the rotation
 
Last edited:
Yes. Exactly.

If you turned one wheel and had someone firmly hold the other rear wheel, the driveshaft would turn.

It's a clever invention that allows the rear wheels to both receive power but also turn at different speeds.

There are disadvantages with the open differential, such as the fact that it feeds more power to the rear wheel that has the least traction.

That's why some cars have a limited-slip differential instead of an open differential. But that's a whole 'nuther story. :friendly_wink:
 
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