Confused- Front drive shaft turns in 2wd while moving??
Joined: Apr 2007
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RE: Confused- Front drive shaft turns in 2wd while moving??
ADDENDUM:
I think some of you may wonder how the center shaft is rotating backwards. Put your truck in park and jack the rear of your truck off the ground. Spin either tire. The other spins opposite (provided you don't have an LSD or locker). If you put the floor jack under one side of the axle so the fron was still on the ground and one rear tire was still on the ground with the transmission in park, you could still push the truck due to the differential. The tire in the air would spin opposite. Remember, the transmission is in park so the driveshaft is absolutely not able to move and doesn't rotate, just like I described in the fron axle.
I know this may be old news to many out there, but it can be confusing. Basically my drawing shows this same concept with the left shaft and center shaft. The two shafts which can be compared to the two rear tires in my above example are able to rotate in opposite directions while the front driveshaft remains stationary in 2WD. The right shaft has no effect on the driveline until the vacuum actuated CAD is engaged by putting the transfer cas in 4WD. Please feel free to post any questions or clarification that you may need as this conecpt is fascinating to me.
I think some of you may wonder how the center shaft is rotating backwards. Put your truck in park and jack the rear of your truck off the ground. Spin either tire. The other spins opposite (provided you don't have an LSD or locker). If you put the floor jack under one side of the axle so the fron was still on the ground and one rear tire was still on the ground with the transmission in park, you could still push the truck due to the differential. The tire in the air would spin opposite. Remember, the transmission is in park so the driveshaft is absolutely not able to move and doesn't rotate, just like I described in the fron axle.
I know this may be old news to many out there, but it can be confusing. Basically my drawing shows this same concept with the left shaft and center shaft. The two shafts which can be compared to the two rear tires in my above example are able to rotate in opposite directions while the front driveshaft remains stationary in 2WD. The right shaft has no effect on the driveline until the vacuum actuated CAD is engaged by putting the transfer cas in 4WD. Please feel free to post any questions or clarification that you may need as this conecpt is fascinating to me.
Joined: Apr 2007
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RE: Confused- Front drive shaft turns in 2wd while moving??
ORIGINAL: Fox Fader
The industry stopped using the locking hubs simply cause turning the axle, diff, and shaft under 2wd was acceptable vs using locking hubs to keep 'em from turning.
The industry stopped using the locking hubs simply cause turning the axle, diff, and shaft under 2wd was acceptable vs using locking hubs to keep 'em from turning.
The 1999-2002 GM/Chevy's had full time rotating front drive shafts. This turned out to be problematic and in 2003 was corrected. Hubs are not the only method to prevent the drive shaft from rotating; as in our trucks and the 88-98 GM/Chevy's, an actuator is used to split the intermediate shaft and allows the two outer shafts to rotate forward freely while the center shaft takes the heat and counter-rotates instead of the drive shaft.
Veteran
Joined: Oct 2006
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RE: Confused- Front drive shaft turns in 2wd while moving??
The biggest reason why the manufacturers stopped using manual lockouts is:
1. The unit bearings are much easier to install on the assembly line.
2. The industry market demands were all about convenience. Push button 4wd and the ease of unit bearings was just plain easier for the consumer to understand and easier to engage and disengage. Shift on the fly was born and the manufacturers never looked back.
The fact is, a full float design with lockout hubs is much stronger and more durable than a unit bearing style like on the Dodge Ram. It is cheaper to service and much, much easier to work on. It allows you to drive with none of the front driveline engaged which means it has way less wear and tear and milage benefits are often seen when converting to a free spin hub style with lockouts.
Another huge advantage for the off roader is that if you have a axle shaft or front axle u-joint break on the trail, you can simply unlock the hub and drive off the trail because nothing in the driveline would be turning. Whereas a broken axle shaft or broken axle u-joint with the standard unit bearings requires an immediate trail fix to get rolling again. Not to mention that unit bearings are significantly more exspensive than full float bearings both in part cost and labor cost.
Another advantage is that you can have the ability to have 2wd low range by putting the transfer case into low range, but leaving the manual hubs disengaged. This is extremely popular with off roaders and trucks used to launch and retreive boats or pulling heavy loads up steep grades.
There is no debating which system is better. Having a full float style front axle with lockout hubs is far superior to the unit bearings that Dodge has used since 1994.
The answer to the question about your front driveshaft spinnig in 2wd with the standard Dodge Ram unit bearings is yes, your driveshaft does turn.
It does not turn 1:1 as if it were in 4wd, and it is not powered, but the front wheels turn the hubs, which turn the stub axle shafts, which turn the inner axle shafts, which (on the drivers side) turns the spider gears, which results in the carrier turning, which means the pinion turns, which means the front driveshaft turns. If you have replaced the front carrier with a LSD or Locker, than you have a full 1:1 effect, but left stock with an open differential, your driveshaft does spin along for the ride, just not at a 1:1 rate.
The transfer case seperates the front and rear drivelines until manipulated by the t-case shift lever which moves the shift fork inside the t-case and then powers the front driveline, but in 2wd, the front driveline is free spinning and not mchanically connected to the powered rear driveline.
Hopefully somebody finds this information helpful.
1. The unit bearings are much easier to install on the assembly line.
2. The industry market demands were all about convenience. Push button 4wd and the ease of unit bearings was just plain easier for the consumer to understand and easier to engage and disengage. Shift on the fly was born and the manufacturers never looked back.
The fact is, a full float design with lockout hubs is much stronger and more durable than a unit bearing style like on the Dodge Ram. It is cheaper to service and much, much easier to work on. It allows you to drive with none of the front driveline engaged which means it has way less wear and tear and milage benefits are often seen when converting to a free spin hub style with lockouts.
Another huge advantage for the off roader is that if you have a axle shaft or front axle u-joint break on the trail, you can simply unlock the hub and drive off the trail because nothing in the driveline would be turning. Whereas a broken axle shaft or broken axle u-joint with the standard unit bearings requires an immediate trail fix to get rolling again. Not to mention that unit bearings are significantly more exspensive than full float bearings both in part cost and labor cost.
Another advantage is that you can have the ability to have 2wd low range by putting the transfer case into low range, but leaving the manual hubs disengaged. This is extremely popular with off roaders and trucks used to launch and retreive boats or pulling heavy loads up steep grades.
There is no debating which system is better. Having a full float style front axle with lockout hubs is far superior to the unit bearings that Dodge has used since 1994.
The answer to the question about your front driveshaft spinnig in 2wd with the standard Dodge Ram unit bearings is yes, your driveshaft does turn.
It does not turn 1:1 as if it were in 4wd, and it is not powered, but the front wheels turn the hubs, which turn the stub axle shafts, which turn the inner axle shafts, which (on the drivers side) turns the spider gears, which results in the carrier turning, which means the pinion turns, which means the front driveshaft turns. If you have replaced the front carrier with a LSD or Locker, than you have a full 1:1 effect, but left stock with an open differential, your driveshaft does spin along for the ride, just not at a 1:1 rate.
The transfer case seperates the front and rear drivelines until manipulated by the t-case shift lever which moves the shift fork inside the t-case and then powers the front driveline, but in 2wd, the front driveline is free spinning and not mchanically connected to the powered rear driveline.
Hopefully somebody finds this information helpful.
Champion
Joined: Aug 2005
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RE: Confused- Front drive shaft turns in 2wd while moving??
Joined: Apr 2007
Posts: 162
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RE: Confused- Front drive shaft turns in 2wd while moving??
ORIGINAL: nhlbill
The answer to the question about your front driveshaft spinnig in 2wd with the standard Dodge Ram unit bearings is yes, your driveshaft does turn.
It does not turn 1:1 as if it were in 4wd, and it is not powered, but the front wheels turn the hubs, which turn the stub axle shafts, which turn the inner axle shafts, which (on the drivers side) turns the spider gears, which results in the carrier turning, which means the pinion turns, which means the front driveshaft turns.
The answer to the question about your front driveshaft spinnig in 2wd with the standard Dodge Ram unit bearings is yes, your driveshaft does turn.
It does not turn 1:1 as if it were in 4wd, and it is not powered, but the front wheels turn the hubs, which turn the stub axle shafts, which turn the inner axle shafts, which (on the drivers side) turns the spider gears, which results in the carrier turning, which means the pinion turns, which means the front driveshaft turns.