Front Drive Shaft Now Turning In 2WD After Re-Gear

[CarbonSteel]

I have never noticed it turning before, but since my re-gearing it does. My wife was moving it the other day and I noticed it turning. I replaced the OEM axles with Dana Spicer chrome moly, but did not remove the FAD and therefore I would not expect it to turn.

I also notice a driveline vibration when at upper highway speeds that was not there before and I am wondering if this is due to the front drive shift turning.

Anyone have an idea of why it is now turning in 2WD? Is this something that will go away after some miles are put on the re-gear?

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[oldcjguy]

Check that your fad is actually disconnecting. See if you can spin the driveshaft by hand. If your transfer case is in 2WD and FAD has the axle disconnected you should be able to turn the driveshaft. If you can't, try jacking up one front tire and see if you can then. If you can spin the shaft and that lifted tire rotates something is keeping that axle connected.

 

[CarbonSteel]

@oldcjguy - the driveshaft will not turn by hand with both wheels on the ground while in 2WD and in park.

I raised each side (independently) and they both turn freely with no binding. However, turning both wheels also turns the driveshaft.

Is the FAD engaged?

 

[oldcjguy]

@oldcjguy - the driveshaft will not turn by hand with both wheels on the ground while in 2WD and in park.

I raised each side (independently) and they both turn freely with no binding. However, turning both wheels also turns the driveshaft.

Is the FAD engaged?

When each wheel turns freely was the driveshaft spinning? Sounds like FAD has axle engaged to me. If FAD had the axle disengaged the spider gears in the diff should turn when spinning the driveshaft while both wheels are on the ground.

Have you tried putting it in 4HI and see if you get an error light for FAD? Also, find some dirt and put it in 4HI. Do a few tight figure 8 turns then put it in 2WD and do some figure 8s again. See if that frees it up. My guess is something is a miss with FAD. Pretty easy to access though, so that's a good thing.

 

[oldcjguy]

@oldcjguy - the driveshaft will not turn by hand with both wheels on the ground while in 2WD and in park.

I raised each side (independently) and they both turn freely with no binding. However, turning both wheels also turns the driveshaft.

Is the FAD engaged?

The other thing it could be is the front locker is locked. If that happens the driveshaft will spin in 2WD. A way to test that is to (while in 2WD) jack up each front wheel, one at a time, and spin it by hand. If the locker is stuck locked, the wheel on the FAD side will spin without spinning the driveshaft and the wheel on the non-FAD side will spin but will turn the driveshaft.

Just throwing out ideas here.

 

[jlewissystem]

The other thing it could be is the front locker is locked. If that happens the driveshaft will spin in 2WD. A way to test that is to (while in 2WD) jack up each front wheel, one at a time, and spin it by hand. If the locker is stuck locked, the wheel on the FAD side will spin without spinning the driveshaft and the wheel on the non-FAD side will spin but will turn the driveshaft.

Just throwing out ideas here.

Good point on here - is there a Tazer involved? If so - are you locked and dont know it? As someone else mentioned: i would cycle the transfer and see if it "pops-out".

 

[CarbonSteel]

When each wheel turns freely was the driveshaft spinning? Sounds like FAD has axle engaged to me. If FAD had the axle disengaged the spider gears in the diff should turn when spinning the driveshaft while both wheels are on the ground.

Have you tried putting it in 4HI and see if you get an error light for FAD? Also, find some dirt and put it in 4HI. Do a few tight figure 8 turns then put it in 2WD and do some figure 8s again. See if that frees it up. My guess is something is a miss with FAD. Pretty easy to access though, so that's a good thing.

Yes; when each wheel is turned (1 jacked up and the other on the ground and vice-versa), the driveshaft turned when the wheel was turned (both passenger and driver).

I have had it both 4HI and 4LO with no warning lights. I have also engaged the lockers with no errors and have done some turns back and forth.

The root of what is driving my questions is that I have a vibration above 70 (which gets worse as speed increases) and I am concerned the driveshaft is the source of the vibration because it is turning when it should not be.

 

[CarbonSteel]

Good point on here - is there a Tazer involved? If so - are you locked and dont know it? As someone else mentioned: i would cycle the transfer and see if it "pops-out".

I do have a Tazer Mini, but if the front locker was on, I would have "turn issues" which I do not. I have gone in and out of 2H/4H/4L a few times since the re-gearing.

I will check the Tazer settings to be sure that I did not accidently enable/disable something.

 

[jlewissystem]

I do have a Tazer Mini, but if the front locker was on, I would have "turn issues" which I do not. I have gone in and out of 2H/4H/4L a few times since the re-gearing.

I will check the Tazer settings to be sure that I did not accidently enable/disable something.

Cool - just to fully eliminate - you could always pull the Tazer. They're great, but not perfect.

 

[CarbonSteel]

Cool - just to fully eliminate - you could always pull the Tazer. They're great, but not perfect.

Just disconnect, but not unmarry--correct?

 

[jlewissystem]

Just disconnect, but not unmarry--correct?

Correct

 

[Chocolate Thunder]

Don’t you have RCV front axles with FAD delete? Wouldn’t this cause your axles to be connected to the differential and thus the front drive shaft all the time, causing it to spin whenever the front tires turn?

 

[oldcjguy]

Yes; when each wheel is turned (1 jacked up and the other on the ground and vice-versa), the driveshaft turned when the wheel was turned (both passenger and driver).

I have had it both 4HI and 4LO with no warning lights. I have also engaged the lockers with no errors and have done some turns back and forth.

The root of what is driving my questions is that I have a vibration above 70 (which gets worse as speed increases) and I am concerned the driveshaft is the source of the vibration because it is turning when it should not be.

Since one wheel turns while the other is on the ground it's not the locker. My money is on the FAD.

The driveshaft is probably the source of the vibration. Turning when it shouldn't be is not hurting anything, but there is probably a minor balance or phasing issue. Since you re-geared, I'm assuming the jeep is lifted so that could make the vibration feel worse. Is the driveshaft factory or aftermarket? If FAD is working correctly you probably don't need to worry about the vibration because you probably don't go that fast off-road. But I don't judge

All that being said, the driveshaft shouldn't be turning. Did you do the gears and axles or a shop? If it was a shop did they definitely put a 2 piece axle for FAD back in or a one piece that eliminates FAD? Pull the cover off the FAD and make sure that slider gear/collar is operating properly.

 

[CarbonSteel]

Don’t you have RCV front axles with FAD delete? Wouldn’t this cause your axles to be connected to the differential and thus the front drive shaft all the time, causing it to spin whenever the front tires turn?

No; I went with the Dana Spicer Chrome Moly axles that retain the FAD:

https://www.danaaftermarket.com/spi...m_content=spicer-nickel-chromoly-axle-shafts-

 

[CarbonSteel]

Since one wheel turns while the other is on the ground it's not the locker. My money is on the FAD.

The driveshaft is probably the source of the vibration. Turning when it shouldn't be is not hurting anything, but there is probably a minor balance or phasing issue. Since you re-geared, I'm assuming the jeep is lifted so that could make the vibration feel worse. Is the driveshaft factory or aftermarket? If FAD is working correctly you probably don't need to worry about the vibration because you probably don't go that fast off-road. But I don't judge

All that being said, the driveshaft shouldn't be turning. Did you do the gears and axles or a shop? If it was a shop did they definitely put a 2 piece axle for FAD back in or a one piece that eliminates FAD? Pull the cover off the FAD and make sure that slider gear/collar is operating properly.

It was a shop and I supplied the axles--Dana Spicer Chrome Moly 2 piece that retains the FAD. I will disconnect the Tazer and drive it a bit to see if it self-corrects, otherwise, I am headed back to the shop.

For the vibration--yep; I am sure the spinning driveshaft is the source. I just need to find out why it is spinning.

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