Novak Conversions Jeep Wrangler YJ shifters

Should front driveshaft turn when not in 4WD?

It is suppose to spin.

Though your passenger axle shaft is disengaged from the vacuum, your driver is, which will cause free movement in the driveshaft. Even if you have a vacuum that is locked all the time, it will make no change.

You transfer case only adds the actual output when the shifter is engaged, which causes the shift fork to move over and engage the 4WD section of the splines on the tail shaft (in laymen terms). That is why you feel no difference while being in 2WD.

It is perfectly normal.

Vehicles that have manual locking hubs will normally notice that their driveshaft does not spin, it is soley because of our auto locking hubs.
 
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Chris said:
No, your front driveshaft will not spin freely in 2WD. Your front axle and driveshaftare always locked and spinning when your vehicle is moving. When you engage the 4wd in the transfer case it then gets power transfer along with the rear wheels.

The connection is inside the transfer case not the front differential.

So the front wheels, the front axles, the differential, and and drive shaft turn all the time. When you engage the vehicle into 4-wheel drive the connection is made inside the transfer case. At that point, the front is actually driving along with the rear.

Older 4-wheel drive vehicles (and some modern 4-wheel drive vehicles) have locking hubs where you can either electronically or manually disengage the hubs so that only the wheels turn and not the rest of the front drivetrain.
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Wait,,,what?? My '92 YJ front driveshaft spins freely when not engaged because it has the vacuum disconnect that splits the front right axle. I'm 99% sure on that but now I need to slide underneath and check it. :)

My problem, I think, it the vacuum servo is not working so it never engages at the front axle but the when the transfer case lever is engaged to 4WD the driveshaft definitely engages to the eng./trans.

Time to get crawling and check.
 
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Haha, just blame Jeep! :)

To Danny H's point I did some troubleshooting and found many vacuum lines were disconnected so I corrected that but still no 4WD. Last item in line is the troublesome vacuum servo on the front axle is shot. I may replace the servo or just manually install a locking collar.

Obviously if I do nothing I'm stuck with only 2WD. Not sure if there's any drawback to permanently locking the axles as long as I keep the transfer case in 2WD until needed.
 
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Danny H said:
Novice here, asking, should the front shaft turn when the 4WD is not engaged? If not, can anyone recommend troubleshooting?
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No, not normal at all. Since the intermediate shaft is not connected via the CAD to the passenger axle shaft which spins full time, there is nothing to spin the intermediate shaft so it sits there unpowered. When the driver side wheel turns, the spider gears rotate and spin the intermediate shaft backwards from the direction of the driver side axle shaft. Therefore, the axle shafts are not turning in the same direction and thus, nothing rotates the ring gear to spin the front driveshaft.

This changes if you add a locker or delete the CAD for a one-piece TJ passenger axle shaft, but otherwise in stock form, no, the front driveshaft does not spin when moving. This is also why when you swap the YJ to a TJ axle shaft and the front begins to spin, often there are new vibrations never felt before.
 
Novak Conversions Jeep Wrangler YJ shifters
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