When does my front driveshaft start spinning?

I've got a 1990 with the D30 disconnect axle and I've had several people explain to me that the disco ones don't spin constantly like the non-disco ones do. Can anyone tell me at about what speed mine starts spinning?

Just to prove it to youself, lift the front in up, both sides, put in N and turn each wheel. You will also understand what the vac disconnect does too after that...

Yours starts spinning when in 4wd.

Otherwise you may have slight spinning due to viscous drag, but it'll be slower than if fully engaged.

What are you worried about?

Bounty Hunter said:

Yours starts spinning when in 4wd.

Otherwise you may have slight spinning due to viscous drag, but it'll be slower than if fully engaged.

What are you worried about?

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Wow I forgot I started this thread. When I have the Heep in 4WD it's been very loud since the addition of my RE3.5" lift. When it's in 2wd it starts doing the same noise only a degree quieter around 55mph. My question is does the front ds start spinning around freeway speeds?

BigBlackHeep said:

Wow I forgot I started this thread. When I have the Heep in 4WD it's been very loud since the addition of my RE3.5" lift. When it's in 2wd it starts doing the same noise only a degree quieter around 55mph. My question is does the front ds start spinning around freeway speeds?

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That's a good question. It's possible that oil viscosity and drag might get it spinning, in the same way a disengaged fan clutch spins without real power, but I would expect that if it did spin it wouldn't be very consistent in speed, and would vary with how hot the oil gets. Of course, if you really want to know for sure, you could take the driveshaft off and see if the noise persists. Or perhaps, since it isn't supposed to spin, and since there shouldn't be very much power behind it, how about getting a bunch of duct tape or something, and temporarily taping the shaft in some way that could prevent it from freewheeling.

Your front driveshaft always spins, whenever you are moving. The disconnect is on one axle-shaft, on one side. The other axle-shaft is always connected to the differential. So when that axle-shaft is spinning (which is whenever the Jeep is moving) the differential and front driveshaft will also be spinning.

The disconnect only disconnects one front half from the other front half. It does not disconnect BOTH front halves from the differential, nor does it disconnect the differential from the front driveshaft.

dmillion said:

Your front driveshaft always spins, whenever you are moving. The disconnect is on one axle-shaft, on one side. The other axle-shaft is always connected to the differential. So when that axle-shaft is spinning (which is whenever the Jeep is moving) the differential and front driveshaft will also be spinning.

The disconnect only disconnects one front half from the other front half. It does not disconnect BOTH front halves from the differential, nor does it disconnect the differential from the front driveshaft.

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You could keep the driveshaft from spinning though. It would cause the half of the passenger side axle to spin the opposite direction of the driver side though. Which would probably just cause more noise if there is something wrong in there. I guess I never really saw the point in only having that one side disconnect. I suppose it may cut down on wear a little.

el_roy1985 said:

You could keep the driveshaft from spinning though.

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I don't see how. Unless you're talking about spending $600+ on one of the manual hub kits.

el_roy1985 said:

I guess I never really saw the point in only having that one side disconnect. I suppose it may cut down on wear a little.

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I think the main point was to prevent any binding when turning. But since there is almost no binding anyway, it is kind of pointless.

dmillion said:

I don't see how. Unless you're talking about spending $600+ on one of the manual hub kits.

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Try it. If you have an unmounted axle around it's easy, or just jack up both wheels of an axle and put your TC in neutral. Rotate one wheel. Does the driveshaft rotate or does the opposite wheel counter-rotate?

Jack up the front end with both wheels off the ground.

When it is put in 4wd the wheels should spin opposite of each other unless, you have a locker or factory limited slip. If you have an open diff and the wheels are both spinning you should be able to get a friend on the opposite wheel and he should be able to keep it from turning as you turn your side.

When it is in 2wd the driver side wheel should spin the drive shaft. The passenger side should not spin the drive shaft. If the passenger side is spinning the drive shaft then it is either still in 4wd or the collar on the disconnect side is not sliding back over when put into 2wd. Or, if the passenger side spins the drive shaft you may have a non-disco axle. You should be able to identify that which, you already have.

So, when the vehicle is in motion in any gear, r/n/d, that driver side wheel is going to cause the drive shaft to spin at any speed in accordance to how fast the rig is moving. The faster you go the faster it will spin and vice versa.

When you have the lock out hubs on them wheels, such as on the d44/60 etc. and they are in the free position the wheels are diconected at the stub axle and the axle shafts nor the drive shaft will spin. HTH

I think the main point was to prevent any binding when turning. But since there is almost no binding anyway, it is kind of pointless.

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You've hit on the reason Dmillion. I traded from an XJ having a discoed diff to a later model non-disco, and I could tell a difference. The disco turned like any other 2WD, but the non-disco turns with a slight scrubbing on low speed tight turns. I probably wouldn't have noticed the scrubbing, except I was going from one model right into the other.

Matthew Currie said:

Try it. If you have an unmounted axle...

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I don't see what this has to do with keeping the driveshaft from spinning when you're driving the Jeep. Maybe I misunderstood and when el_roy1985 said that you could keep the front driveshaft from spinning he was only talking about when it is jacked up. When it is jacked up and in 2WD it won't spin, because it is not connected to power within the transfer case. When it is jacked up and in 4WD the front driveshaft is going to spin, regardless of anything else (holding a tire or whatever), because it then it IS connected to power in the transfer case.

The bottome line here is pretty simple: Your front driveshaft turns whenever your Jeep is moving--fast, slow, it doesn't matter. The only way to stop that is to put on manually-disconnecting hubs (very expensive), or to disconnect the driveshaft from the differential (not something you want to do after every 4x4 outing!).

dmillion said:

I don't see what this has to do with keeping the driveshaft from spinning when you're driving the Jeep. Maybe I misunderstood and when el_roy1985 said that you could keep the front driveshaft from spinning he was only talking about when it is jacked up. When it is jacked up and in 2WD it won't spin, because it is not connected to power within the transfer case. When it is jacked up and in 4WD the front driveshaft is going to spin, regardless of anything else (holding a tire or whatever), because it then it IS connected to power in the transfer case.

The bottome line here is pretty simple: Your front driveshaft turns whenever your Jeep is moving--fast, slow, it doesn't matter. The only way to stop that is to put on manually-disconnecting hubs (very expensive), or to disconnect the driveshaft from the differential (not something you want to do after every 4x4 outing!).

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I think the original question was when or whether the driveshaft spins when one is driving in 2WD, with axle disconnected. If you have a disconnect axle, and you are in 2WD, there is no power to the driveshaft, and when the left wheel turns, it will probably counter-rotate the right inner axle, rather than rotating the driveshaft. If it does start the driveshaft rotating, it will do so only to the extent that the right inner axle is stiffer or more resistant to turning through the spider gears than the ring-and-pinion and driveshaft are resistant to turning.

That's why I suggested jacking up an axle. If you jack up an axle, or have one without wheels on it, and turn the left axle shaft alone, what happens then will be the same thing that happens when a disconnected D30 rolls along the road in 2WD, the only difference being that the entire right axle will counter-rotate, instead of just the inner axle.

This is, by the way, why the flat-towing instructions for disconnect-axle Jeeps call for putting the TC in neutral, rather than the transmission. In neutral position the TC vacuum switch connects the axle, and without this engagement, the front driveshaft will not turn, and without the driveshaft turning the TC will not be lubricated when flat towing.

Thanks for all the suggestions guys. Once the weather warms up I'll try the jack up method.