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should the front driveshaft spin freely in 2h
- Thread starter xxxt101
- Start date
from GM's service manual:
Front Drive Axle Description and Operation
Selectable Four Wheel Drive (S4WD) Front Axle Description and Operation
The Selectable Four Wheel Drive (S4WD) Front Axle consist of the following components:
? Differential Carrier Housing
? Differential Assembly
? Output Shafts (Left and Right Side)
? Inner Axle Shaft Housing
? Inner Axle Shaft (Right Side)
? Clutch Fork
? Clutch Fork Sleeve
? Electric Motor Actuator
The front axle on Selectable Four Wheel Drive model vehicles uses a central disconnect feature in order to engage and disengage the front axle. When the driver engages the 4WD system, the Transfer Case Control Module sends a signal to the electric motor actuator to energize and extend the plunger inside. The extended plunger moves the clutch fork and clutch fork sleeve across the inner axle shaft and the clutch fork shaft and locks the two shafts together. The locking of the two shafts allows the axle to operate in the same manner as a semi-floating rear axle. A propeller shaft connects the transfer case to the front axle. The differential carrier assembly uses a conventional ring and pinion gear set to transmit the driving force of the engine to the wheels. The open differential allows the wheels to turn at different rates of speed while the axle continues to transmit the driving force. This prevents tire scuffing when going around corners and premature wear on internal axle parts. The ring and pinion set and the differential are contained within the carrier. The axle identification number is located on top of the differential carrier assembly or on a label on the bottom of the right half of differential carrier assembly. The drive axles are completely flexible assemblies consisting of inner and outer constant velocity CV joints protected by thermoplastic boots and connected by a wheel drive shaft.
Transfer Case Description and Operation
The NVG 236/246 transfer case features a 4 button shift control switch located on the instrument panel. When the vehicle has the ignition key in the RUN position, the transfer case shift control module starts monitoring the transfer case shift control switch to determine if the driver desires a new mode/gear position. At a single press of the transfer case shift control switch, the lamp of the new desired position will begin flashing to inform the driver that the transfer case shift control module has received the request for a new mode/gear position. The lamp will continue to flash until all shifting criteria has been met and the new mode/gear position has been reached, or has been engaged. Once the new mode/gear position is fully active, the switch indicator lamp for the new position will remain ON constantly.
During normal driving situations the transfer case can operate in the Auto 4WD mode. In the Auto 4WD mode the transfer case shift control module monitors rear wheel slip speed, based on the inputs from both the front and rear propshaft speed sensors. When the vehicle experiences a rear wheel slip condition, the transfer case shift control module sends a pulse width modulated (PWM) signal to an electronic motor, which is the transfer case encoder motor. This motor rotates the transfer case sector shaft, applying a clutch pack. This clutch pack is designed to deliver a variable amount of torque, normally delivered to the rear wheels, and transfers it to the front wheels. Torque is then ramped up to the front wheels until the front propshaft speed sensor matches that of the rear propshaft speed sensor. Torque is then ramped down until torque is completely removed from the front wheels or until rear wheel slip is once again detected. The process would then repeat.
The NVG 236/246 transfer case has the added feature of also providing the driver with 3 manual mode/gear positions:
? 4HI - 4 Wheel Drive high range
? 2HI - 2 Wheel Drive high range
? 4LO - 4 Wheel Drive low range
The driver may choose to select any of these mode/gear positions while driving the vehicle. However, the transfer case will not allow a shift into or out of 4LO unless the following criteria has been met:
? The engine is running.
? The automatic transmission is in Neutral, clutch depressed on manual transmissions.
? The vehicle speed is below 5 km/h (3 mph).
This transfer case also has a Neutral position. A shift to the Neutral position allows the vehicle to be towed without the rear axle rotating the transfer case main shaft and the transmission output shaft. Neutral position may be obtained only if the following criteria has been met:
? The key is ON.
? The automatic transmission is in Neutral, clutch depressed on manual transmissions.
? The vehicle speed is below 5 km/h (3 mph).
? The transfer case is in 2HI mode.
Once these conditions have been met, press and hold both the 2HI and 4LO buttons for 10 seconds. When the system completes the shift to neutral, the red neutral lamp will illuminate.
View the list of major components that make up the automatic transfer case (ATC) system below.
end of manual info.
From the info above, the front prop shaft is directly coupled to the differential carrier (via ring and pinion). what is unclear is if the carrier is permanently coupled to one inner axle shaft or not. if it is, then turning the prop shaft should turn one wheel only. if the carrier is NOT permanently coupled with one inner shaft, then turning the prop shaft will not turn either wheel, HOWEVER, it will cause the carrier to rotate inside the housing, and that would cause a certain amount of resistance felt at the prop shaft.
I've never looked at mine in operation, so i don't know the exact answer. but at least you should have a better understanding of what is happening in the different modes.
good luck. paul.
Front Drive Axle Description and Operation
Selectable Four Wheel Drive (S4WD) Front Axle Description and Operation
The Selectable Four Wheel Drive (S4WD) Front Axle consist of the following components:
? Differential Carrier Housing
? Differential Assembly
? Output Shafts (Left and Right Side)
? Inner Axle Shaft Housing
? Inner Axle Shaft (Right Side)
? Clutch Fork
? Clutch Fork Sleeve
? Electric Motor Actuator
The front axle on Selectable Four Wheel Drive model vehicles uses a central disconnect feature in order to engage and disengage the front axle. When the driver engages the 4WD system, the Transfer Case Control Module sends a signal to the electric motor actuator to energize and extend the plunger inside. The extended plunger moves the clutch fork and clutch fork sleeve across the inner axle shaft and the clutch fork shaft and locks the two shafts together. The locking of the two shafts allows the axle to operate in the same manner as a semi-floating rear axle. A propeller shaft connects the transfer case to the front axle. The differential carrier assembly uses a conventional ring and pinion gear set to transmit the driving force of the engine to the wheels. The open differential allows the wheels to turn at different rates of speed while the axle continues to transmit the driving force. This prevents tire scuffing when going around corners and premature wear on internal axle parts. The ring and pinion set and the differential are contained within the carrier. The axle identification number is located on top of the differential carrier assembly or on a label on the bottom of the right half of differential carrier assembly. The drive axles are completely flexible assemblies consisting of inner and outer constant velocity CV joints protected by thermoplastic boots and connected by a wheel drive shaft.
Transfer Case Description and Operation
The NVG 236/246 transfer case features a 4 button shift control switch located on the instrument panel. When the vehicle has the ignition key in the RUN position, the transfer case shift control module starts monitoring the transfer case shift control switch to determine if the driver desires a new mode/gear position. At a single press of the transfer case shift control switch, the lamp of the new desired position will begin flashing to inform the driver that the transfer case shift control module has received the request for a new mode/gear position. The lamp will continue to flash until all shifting criteria has been met and the new mode/gear position has been reached, or has been engaged. Once the new mode/gear position is fully active, the switch indicator lamp for the new position will remain ON constantly.
During normal driving situations the transfer case can operate in the Auto 4WD mode. In the Auto 4WD mode the transfer case shift control module monitors rear wheel slip speed, based on the inputs from both the front and rear propshaft speed sensors. When the vehicle experiences a rear wheel slip condition, the transfer case shift control module sends a pulse width modulated (PWM) signal to an electronic motor, which is the transfer case encoder motor. This motor rotates the transfer case sector shaft, applying a clutch pack. This clutch pack is designed to deliver a variable amount of torque, normally delivered to the rear wheels, and transfers it to the front wheels. Torque is then ramped up to the front wheels until the front propshaft speed sensor matches that of the rear propshaft speed sensor. Torque is then ramped down until torque is completely removed from the front wheels or until rear wheel slip is once again detected. The process would then repeat.
The NVG 236/246 transfer case has the added feature of also providing the driver with 3 manual mode/gear positions:
? 4HI - 4 Wheel Drive high range
? 2HI - 2 Wheel Drive high range
? 4LO - 4 Wheel Drive low range
The driver may choose to select any of these mode/gear positions while driving the vehicle. However, the transfer case will not allow a shift into or out of 4LO unless the following criteria has been met:
? The engine is running.
? The automatic transmission is in Neutral, clutch depressed on manual transmissions.
? The vehicle speed is below 5 km/h (3 mph).
This transfer case also has a Neutral position. A shift to the Neutral position allows the vehicle to be towed without the rear axle rotating the transfer case main shaft and the transmission output shaft. Neutral position may be obtained only if the following criteria has been met:
? The key is ON.
? The automatic transmission is in Neutral, clutch depressed on manual transmissions.
? The vehicle speed is below 5 km/h (3 mph).
? The transfer case is in 2HI mode.
Once these conditions have been met, press and hold both the 2HI and 4LO buttons for 10 seconds. When the system completes the shift to neutral, the red neutral lamp will illuminate.
View the list of major components that make up the automatic transfer case (ATC) system below.
end of manual info.
From the info above, the front prop shaft is directly coupled to the differential carrier (via ring and pinion). what is unclear is if the carrier is permanently coupled to one inner axle shaft or not. if it is, then turning the prop shaft should turn one wheel only. if the carrier is NOT permanently coupled with one inner shaft, then turning the prop shaft will not turn either wheel, HOWEVER, it will cause the carrier to rotate inside the housing, and that would cause a certain amount of resistance felt at the prop shaft.
I've never looked at mine in operation, so i don't know the exact answer. but at least you should have a better understanding of what is happening in the different modes.
good luck. paul.
I think that the front drive shaft is locked into the transfer case so it will only turn with the tranfer case.
If you had the back wheels off the ground and in 2hi you put it in gear the back wheels would turn and not the front wheels, but the front drive shaft would turn or in 2hi you could jack up the front wheels and turn them with out turning the front drive shaft.
If you had the back wheels off the ground and in 2hi you put it in gear the back wheels would turn and not the front wheels, but the front drive shaft would turn or in 2hi you could jack up the front wheels and turn them with out turning the front drive shaft.
dmcc1000
Full Member
I may be wrong here but I believe because we do not have manual locking hubs our shafts always spin? I notice that at low speed full wheel lock mine has the tell tale binding of the cv joints.
Den
Den
dmcc1000 said:
The axle CV shafts will always turn with the tires. The end of the shaft has a spline that is locked into the front hubs, which in turn are bolted to the wheels. in 4wd the cv shafts are locked together internally and act as a solid shaft. The binding is caused by the different tracking radius between the front and rear axles during a turn.
Wazbro said:
If you look at the operation description for the transfer case above, the front prop shaft is engaged by a clutch, so in 2wd, the transfer case does not drive the front prop shaft.
Good info, here are my thoughts. From the info above it doesn't seem like the front drive shaft is connected to the front axles at all in 2HI. Because the disconnect is right after the diff. gears. Mine doesn't spin by hand either when in 2hi and all 4 wheels sitting on the ground. I'm thinking the clutch pack in the transfer case doesn't ever fully disengage. You can't really get much leverage by hand on the front drive shaft, so even if the clutch pack was just sitting together, it might be enough resistance to keep it from turning. Besides if the clutch pack is engaged it doesn't matter 2 bits until the front axle connects.
Now here is another question, is the clutch pack in operation when in 4HI/LO or is there a straight shaft that locks. So when I shift into 4HI/LO does the clutch just fully engage or does a shaft bypass the clutch and fully lock both drive shafts?
Now here is another question, is the clutch pack in operation when in 4HI/LO or is there a straight shaft that locks. So when I shift into 4HI/LO does the clutch just fully engage or does a shaft bypass the clutch and fully lock both drive shafts?
pmt257 said:
I wish I could post the service diagram, but I haven't been able to figure out how to pull it out of the system. In any case, There is no clutch pack in the differential. It is an OPEN differential, ergo no clutches. It does have spider gears to allow the front axles to rotate at different speeds. Reread the front axle operation. The clutch fork they refer to is used to couple/decouple the "Front Drive Axle Inner Shaft" and "Front Drive Axle Clutch Shaft" for the right hand axle via what looks like a splined sleeve. The left side has only a "Front Drive Axle Inner Shaft" that goes directly onto the differential carrier.
I suspect that if you pick up the left front tire off the ground, that rotating it will cause the front drive (propeller) shaft to turn. And if you pick up the right tire and rotate it, the front drive shaft will NOT rotate.
Anyone want to try this out and set this issue to rest? Unfortunately it's 22 degrees out right now and I don't have access to a floor jack anyway.
paul.
.....................being that both (right & left) CV axles, are splined into and drive the front wheel hubs indentically ( they're indentical too), both would inturn rotate if you were to apply the lifting and manually spinning the individual wheel scenario. Independently of course, unless the differental itself is being driven by the transfer case.
I am hoping that the diagram will post so We can all see it.
Numbers refer to Exploded Diagram.
(1) Front Drive Axle Inner Shaft
(2) Front Drive Axle Inner Shaft Seal
(3) Front Drive Axle Inner Axle Shaft Bearing
(4) Front Drive Axle Inner Shaft Housing
(5) Front Drive Axle Clutch Gear Thrust Washer
(6) Front Drive Axle Clutch Gear
(7) Front Drive Axle Inner Shaft Retaining Ring
(8 ) Front Drive Axle Clutch Sleeve
(9) Front Drive Axle Clutch Gear Shim
(10) Front Drive Axle Actuator
(11) Front Drive Axle Inner Shaft Housing Bolt
(12) Front Drive Axle Clutch Fork Shaft
(13) Front Drive Axle Clutch Fork Outer Spring
(14) Front Drive Axle Clutch Fork
(15) Front Drive Axle Clutch Fork Shaft Retaining Ring
(16) Front Drive Axle Clutch Fork Inner Spring
(17) Front Drive Axle Clutch Shaft Bearing
(1
Front Drive Axle Clutch Shaft
(19) Front Differential Carrier Case Half Bolt
(20) Front Differential Carrier Case Half
(21) Front Differential Case Half Lock Pin
(22) Front Differential Case Half Lock Pin
(23) Front Differential Bearing Adjuster Nut Lock
(24) Front Drive Axle Clutch Shaft Bearing
(25) Front Differential Bearing Adjuster Nut
(26) Front Differential Bearing Adjuster Nut Sleeve
(27) Front Differential Side Bearing Cup
(2 Front Differential Side Bearing
(29) Front Differential Ring Gear Bolt
(30) Front Differential Pinion Gear Shaft
(31) Front Differential Case
(32) Differential Pinion Gear Shaft Lock Bolt
(33) Differential Side Bearing
(34) Differential Side Bearing Cup
(35) Front Differential Ring Gear
(36) Differential Side Gear Thrust Washer
(37) Differential Side Gear
(3 Differential Pinion Gear Thrust Washer
(39) Differential Pinion Gear
(40) Differential Pinion Gear
(41) Differential Pinion Gear Thrust Washer
(42) Differential Side Gear
(43) Differential Side Gear Retainer
(44) Differential Side Gear Thrust Washer
(45) Front Differential Bearing Adjuster Nut Sleeve
(46) Front Differential Bearing Adjuster Nut
(47) Front Differential Bearing Adjuster Nut Lock
(4 Front Differential Carrier Bushing
(49) Front Differential Carrier Case Half
(50) Front Differential Drive Pinion Gear Outer Bearing
(51) Front Differential Drive Pinion Gear Outer Bearing Cup
(52) Front Differential Drive Pinion Gear Oil Seal
(53) Front Differential Drive Pinion Gear Deflector
(54) Front Differential Drive Pinion Gear Yoke
(55) Front Differential Drive Pinion Gear Yoke Washer
(56) Front Differential Drive Pinion Gear Yoke Nut
(57) Front Differential Carrier Bushing
(5 Front Differential Inner Shaft Bearing
(59) Front Differential Inner Shaft Seal
(60) Front Drive Axle Inner Shaft
(61) Front Differential Carrier Vent
(62) Front Axle Vent Hose
(63) Clamp
(64) Front Differential Carrier Vent Hose Connector
(65) Front Differential Carrier Oil Drain Plug
(66) Front Differential Carrier Oil Drain Plug Washer
(67) Front Differential Carrier Oil Fill Plug
(6 Front Differential Carrier Oil Fill Plug Washer
(69) Front Differential Drive Pinion Gear Bearing Spacer
(70) Front Differential Drive Pinion Gear Inner Bearing Cup
(71) Front Differential Drive Pinion Gear Inner Bearing
(72) Front Differential Drive Pinion Gear Bearing Shim
(73) Front Differential Drive Pinion Gear
Numbers refer to Exploded Diagram.
(1) Front Drive Axle Inner Shaft
(2) Front Drive Axle Inner Shaft Seal
(3) Front Drive Axle Inner Axle Shaft Bearing
(4) Front Drive Axle Inner Shaft Housing
(5) Front Drive Axle Clutch Gear Thrust Washer
(6) Front Drive Axle Clutch Gear
(7) Front Drive Axle Inner Shaft Retaining Ring
(8 ) Front Drive Axle Clutch Sleeve
(9) Front Drive Axle Clutch Gear Shim
(10) Front Drive Axle Actuator
(11) Front Drive Axle Inner Shaft Housing Bolt
(12) Front Drive Axle Clutch Fork Shaft
(13) Front Drive Axle Clutch Fork Outer Spring
(14) Front Drive Axle Clutch Fork
(15) Front Drive Axle Clutch Fork Shaft Retaining Ring
(16) Front Drive Axle Clutch Fork Inner Spring
(17) Front Drive Axle Clutch Shaft Bearing
(1
Front Drive Axle Clutch Shaft (19) Front Differential Carrier Case Half Bolt
(20) Front Differential Carrier Case Half
(21) Front Differential Case Half Lock Pin
(22) Front Differential Case Half Lock Pin
(23) Front Differential Bearing Adjuster Nut Lock
(24) Front Drive Axle Clutch Shaft Bearing
(25) Front Differential Bearing Adjuster Nut
(26) Front Differential Bearing Adjuster Nut Sleeve
(27) Front Differential Side Bearing Cup
(2
Front Differential Side Bearing (29) Front Differential Ring Gear Bolt
(30) Front Differential Pinion Gear Shaft
(31) Front Differential Case
(32) Differential Pinion Gear Shaft Lock Bolt
(33) Differential Side Bearing
(34) Differential Side Bearing Cup
(35) Front Differential Ring Gear
(36) Differential Side Gear Thrust Washer
(37) Differential Side Gear
(3
Differential Pinion Gear Thrust Washer (39) Differential Pinion Gear
(40) Differential Pinion Gear
(41) Differential Pinion Gear Thrust Washer
(42) Differential Side Gear
(43) Differential Side Gear Retainer
(44) Differential Side Gear Thrust Washer
(45) Front Differential Bearing Adjuster Nut Sleeve
(46) Front Differential Bearing Adjuster Nut
(47) Front Differential Bearing Adjuster Nut Lock
(4
Front Differential Carrier Bushing (49) Front Differential Carrier Case Half
(50) Front Differential Drive Pinion Gear Outer Bearing
(51) Front Differential Drive Pinion Gear Outer Bearing Cup
(52) Front Differential Drive Pinion Gear Oil Seal
(53) Front Differential Drive Pinion Gear Deflector
(54) Front Differential Drive Pinion Gear Yoke
(55) Front Differential Drive Pinion Gear Yoke Washer
(56) Front Differential Drive Pinion Gear Yoke Nut
(57) Front Differential Carrier Bushing
(5
Front Differential Inner Shaft Bearing (59) Front Differential Inner Shaft Seal
(60) Front Drive Axle Inner Shaft
(61) Front Differential Carrier Vent
(62) Front Axle Vent Hose
(63) Clamp
(64) Front Differential Carrier Vent Hose Connector
(65) Front Differential Carrier Oil Drain Plug
(66) Front Differential Carrier Oil Drain Plug Washer
(67) Front Differential Carrier Oil Fill Plug
(6
Front Differential Carrier Oil Fill Plug Washer (69) Front Differential Drive Pinion Gear Bearing Spacer
(70) Front Differential Drive Pinion Gear Inner Bearing Cup
(71) Front Differential Drive Pinion Gear Inner Bearing
(72) Front Differential Drive Pinion Gear Bearing Shim
(73) Front Differential Drive Pinion Gear
Attachments
pmt257 said:
oh!! sorry, my bad!
mea culpa, mea culpa, mea culpa!
03whitediamond said:
I understand that the cv axles are locked into the front hubs by splines, but I am not referring to the internal differential parts. If you look at item 60, it looks like it engages the diff carier. On the other side, item 1 is coupled to item 18 using clutch parts 5 through 17. In 2wd, item 1 will free-wheel as it is not coupled via the clutch.
Ah! Ha! ...........having reread xx101 post...................though not absolutely clear, that they meant "transfer case driveshaft- to the differental", I , mistakeningly thought they were referring to CV axles. Anywho's it sounds like, their AV really isn't in 2wd, but for some reason either 4 hi or low. No matter what the dash switch indicater is showing. It "would seem" impossible that the transfercase to differental driveshaft be engaged (turning otherwise). Appropriately in most circumstances the asumption would be made that the underlying cause be in the transfer case, and probably is.
But, it is also possible that the front differental clutching and gear circuit be damaged ( or a malfunctioning Front Drive Axle Actuator) and thus the differental gearing be engaged, locked or frozen together, and thus the turning of either or both front wheels would inturn cause the front differental to transfer driveshaft to turn as well, as though it ( the front driveshaft) were being driven by the transfercase, and in reverse or opposites of normal thinking operation. Of course there wouldn't be any real relationship to the internal gearing circuit of the transfercase ( nor problems if any exist) and the normal rotational turning of the front driveshaft itself in this scenario. If this were to be the scenario,,,,,,,,,,,,, The front driveshaft would be being "turned" by a malfunctioning differental and not be being "driven" by the transfer case and power train circuit. Hmmmmmmmmmm........
But, it is also possible that the front differental clutching and gear circuit be damaged ( or a malfunctioning Front Drive Axle Actuator) and thus the differental gearing be engaged, locked or frozen together, and thus the turning of either or both front wheels would inturn cause the front differental to transfer driveshaft to turn as well, as though it ( the front driveshaft) were being driven by the transfercase, and in reverse or opposites of normal thinking operation. Of course there wouldn't be any real relationship to the internal gearing circuit of the transfercase ( nor problems if any exist) and the normal rotational turning of the front driveshaft itself in this scenario. If this were to be the scenario,,,,,,,,,,,,, The front driveshaft would be being "turned" by a malfunctioning differental and not be being "driven" by the transfer case and power train circuit. Hmmmmmmmmmm........
ok i thank you all for the info but heres what i found out picked up a used front diff and a used transfercase and already installed the front diff and it works great . now heres what i found out about the transfercase the used one i picked up was the same way as the one in the av so therefore this year of avs transfercase only has 4h neutral and 4 low in it the only thing the 2h button really does is unlock the actuator on the front rearend unlocking your axels only so therefore the front driveshaft does spin all the time . so it actually acts like a all wheeldrive transfercase spining the front and back driveshafts at all times . and you wonder why these avs have problems with there front diffs going out the reason being is that the front gears are spinning all the time i really hope they fixed this problem in newer years than the 2002 because its really a bad design . thanks again for your responses
Hey, guys, just to shed a little light on the subject...
I had to change the Bank1 Sensor1, O2 sensor on my 2002. In order to comfortably reach the plug, I disconnected the front propeller shaft. When I was reinstalling the bolts, afterward the shaft turned as I tried to tighten the strap bolts for the u-joint. The Av was in 2Hi, and the shaft was able to turn. I know all the other gear selections work correctly. Driving in this weather, lately, I've had the opportunity to use them all. And, I can definitely feel the difference in each.
So, to answer the OP question, I think it is , Yes.
EJ
I had to change the Bank1 Sensor1, O2 sensor on my 2002. In order to comfortably reach the plug, I disconnected the front propeller shaft. When I was reinstalling the bolts, afterward the shaft turned as I tried to tighten the strap bolts for the u-joint. The Av was in 2Hi, and the shaft was able to turn. I know all the other gear selections work correctly. Driving in this weather, lately, I've had the opportunity to use them all. And, I can definitely feel the difference in each.
So, to answer the OP question, I think it is , Yes.
EJ