4WD transmission system operation - Revision history

Bosanek: Moved the solutions for stuck transfer box in 4WD and transfer box out of sequence from this article into article " 4WD transmission failure diagnostics"

2021-03-15T09:19:19Z

Moved the solutions for stuck transfer box in 4WD and transfer box out of sequence from this article into article " 4WD transmission failure diagnostics"

Bosanek: Typo

2021-03-15T07:24:05Z

Typo

Bosanek: Note correction about 5th gear in 4WD-L mode

2021-03-15T07:23:03Z

Note correction about 5th gear in 4WD-L mode

Bosanek: Improved explanations of transmission mode shifting sequences

2021-03-15T07:21:05Z

Improved explanations of transmission mode shifting sequences

Show changes

Bosanek: Wrote new chapter on 4WD transmission operation modes

2021-03-11T11:16:36Z

Wrote new chapter on 4WD transmission operation modes

Bosanek: More small notes about transmission mode change sequences

2021-03-10T15:00:51Z

More small notes about transmission mode change sequences

Bosanek: Additional notes about the vacuum system

2021-03-10T14:47:08Z

Additional notes about the vacuum system

Bosanek: Additional notes about general 4WD architecture overview

2021-03-10T14:39:32Z

Additional notes about general 4WD architecture overview

Bosanek: Added several general automotive terms wikipedia links

2021-03-10T11:08:37Z

Added several general automotive terms wikipedia links

Bosanek: Link correction

2021-03-04T14:03:34Z

Link correction

@@ Line 305: / Line 305: @@
-# It's only then possible to shift back to 2WD by pressing the 2WD button (and faking the return signal from the vacuum system again if needed).
+It's only then possible to shift back to 2WD by pressing the 2WD button (and faking the return signal from the vacuum system again if needed). This time the controller will command the actuator in the transfer box to disengage the front propeller shaft - the procedure is essentially the reverse of the engagement.
 To "fake" the vacuum formation signal in order to fool the 4WD controller that the vacuum system works, look under the battery tray where you will see two valves (VSV1 and VSV2). UNDERNEATH these is a vacuum sensor with a white connector and two wires. Short out the connector with a bit of wire to make the controller think the sensor has operated. This fakes that the vacuum is good and the 4WD system will complete its cycles ok.
@@ Line 346: / Line 331: @@
 * The shifting procedure back from 4WD-L to 4WD-H is essentially the same, with the same conditions.
 * The only difference is that the actuator is doing the opposite job in the transfer box, and that the "L" lamp on the instrument panel changes its condition from "ON" to "OFF".

@@ Line 97: / Line 97: @@
 There are three operational types of free wheeling hub heads:
-*# Manually operated;
+# Manually operated;
-*# Pneumatically (usually vacuum) operated;
+# Pneumatically (usually vacuum) operated;
-*# Automatically (un)locking;
+# Automatically (un)locking;

@@ Line 53: / Line 53: @@
 #* All the same as 4WD-H, but with low range gearing engaged.
 #** This makes each transmission gear roughly half as slow but with roughly twice as much torque at the wheels.
-#* Application of strong throttle or strong engine braking should be avoided in this transmission mode.
+#* Application of strong throttle or strong engine braking should be avoided in 5th gear in this transmission mode.

← Older revision		Revision as of 11:16, 11 March 2021
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	The only operational differences among different Jimny 3 editions / revisions are in the design of the control of the transmission system.		The only operational differences among different Jimny 3 editions / revisions are in the design of the control of the transmission system.
		+
		+
		+	== 4WD transmission operation modes ==
		+
		+
		+	Three 4WD transmission operation modes are available in all Jimnys 3 which have 4WD:
		+	# 2WD(-H) - two wheel drive high range.
		+	#* Engine torque is transmitted only to the rear axle (rear two wheels) in "normal" (high) range gear mode.
		+	#* This is the default transmission mode meant for regular on-road driving.
		+	# 4WD(-H) - four wheel drive high range.
		+	#* Engine torque is transmitted in fixed 50:50 ratio to both axles (all four wheels), still in the same "normal" (high) range gear mode as in 2WD-H.
		+	#* As there is no center (inter-axle) differential, a wheel skipping / sliding / skidding has to occur when the vehicle turns in any direction in this transmission mode.
		+	#** Otherwise, [https://en.wikipedia.org/wiki/Driveline_windup driveline / transmission wind-up] issues develop.
		+	#** Therefore, this mode should be used only on very slippery surfaces.
		+	# 4WD-L - four wheel drive low range.
		+	#* All the same as 4WD-H, but with low range gearing engaged.
		+	#** This makes each transmission gear roughly half as slow but with roughly twice as much torque at the wheels.
		+	#* Application of strong throttle or strong engine braking should be avoided in this transmission mode.
		+
		+
		+	* Jimny 4WD transmission systems are also technically capable to operate in 2WD-L (two wheel drive low range) mode.
		+	* However, Suzuki chose not to provide a way to shift into this transmission mode.
		+	* 2WD-L mode provides all the benefits of low range gearing without the limitations of 4WD mode without inter-axle differential.
		+	* Wiki article [[2WD-L transmission mode\|'''"2WD-L transmission mode"''']] deals with the topic of making it possible to use this transmission mode as well.

@@ Line 156: / Line 156: @@
-* In the older (lever operated) transmission system, the 4WD controller just operates the vacuum system for the (dis)engagement of the front wheel hub heads and informs the ABS computer upon successful completion of the entire process - all this after sensing that the driver has manually shifted the mechanical bits in the transfer box.
+* In the older (lever operated) transmission system, the 4WD controller just operates the vacuum system for the (dis)engagement of the front wheel hub heads and informs the ABS computer (if present) upon successful completion of the entire process - all this after sensing that the driver has manually shifted the mechanical bits in the transfer box.
 * The driver manually operates the 4WD selection mechanisms in the transfer box at will.
@@ Line 163: / Line 163: @@
-# The driver operates the mechanical transmission lever from 2WD to 4WD, which physically moves the bits in the transfer box, which connect the front propeller shaft to the transfer box.
+# The driver operates the mechanical transmission lever from 2WD to 4WD.
-# The 4WD controller senses this change in the lever position and monitors (by a dedicated sensor in the transfer box) if the mechanical engagement in the transfer box has completed successfully.
+#* This action physically moves the bits in the transfer box, which connect the front propeller shaft to the transfer box.
-# If the 4WD controller detects that the transfer box has completed the change successfully, then the 4WD controller changes the condition of the green 4WD light on the instrument panel from "off" to "flashing", and sends the signal to the vacuum system (valves and switches) to send the vacuum to the front wheel hub heads, in order to engage them.
+# The 4WD controller senses this change of lever position and then monitors (by a dedicated sensor in the transfer box) if the mechanical engagement in the transfer box has completed successfully.
-# The 4WD controller waits a bit to get a return signal from the vacuum system if the vacuum is achieved (this is officially considered an indication that the hub heads should have engaged).
+# If the 4WD controller detects that the transfer box has completed the change successfully, then the 4WD controller changes the condition of the green 4WD light on the instrument panel from "OFF" to "flashing", and sends the signal to the vacuum system (valves and switches) to send the vacuum to the front wheel hub heads, in order to engage them.
 # If the 4WD controller receives a return signal from the vacuum system before time-out, the 4WD controller changes the condition of the green 4WD light on the instrument panel from "flashing" to "ON" and also sends the signal to the ABS controller (another computer in the vehicle - if the vehicle has ABS) that 4WD transmission is engaged, so that the ABS controller can adjust the operation of the ABS system accordingly.
 # The process of shifting the transmission from 2WD to 4WD-H is formally complete.
@@ Line 175: / Line 177: @@
 If the 4WD controller does not receive a positive signal from the transfer box in step 2 of the above process:
-# The 4WD controller will change the state of the green 4WD light on the instrument panel from "off" to flashing" and will not even attempt to engage the vacuum system.
+# The 4WD controller will change the state of the green 4WD light on the instrument panel from "OFF" to flashing" and will not even attempt to engage the vacuum system.
 # The green 4WD light will remain in the "flashing" state until the driver manually disengages the transmission lever back to 2WD mode.
-# Only then will the 4WD controller turn off the green 4WD light.
+# Only then will the 4WD controller turn OFF the green 4WD light.
@@ Line 187: / Line 189: @@
 # The ABS controller will receive no signal about the engagement of 4WD operation;
 # The transfer box will still remain in 4WD mode, because it is operated by a mechanical lever, until the user shifts the lever back to 2WD mode.
@@ Line 195: / Line 198: @@
 # The driver shifts the transmission lever from 4WD-H to 4WD-L position - under the condition that the vehicle is stationery and that the clutch pedal is pressed (for vehicles with a manual gear box) or that SOMETHING IS (for vehicles with an automatic gear box). ''If those two conditions are not fulfilled, it will not be possible (or will be very hard) to shift the lever.'' - TRUE?
 # The 4WD controller senses this change in the lever position and monitors (by a dedicated sensor in the transfer box) if the mechanical shift in the transfer box has completed successfully.
-# If the 4WD controller detects that the transfer box has completed the change successfully, then the 4WD controller changes the condition of the yellow "L" light on the instrument panel from "off" to "on" state, and simultaneously sounds a single beep sound.
+# If the 4WD controller detects that the transfer box has successfully completed the change to low range gearing mode, then the 4WD controller changes the condition of the yellow "L" light on the instrument panel from "OFF" to "ON" state, and simultaneously sounds a single beep sound.
@@ Line 204: / Line 207: @@
-* In the newer (push-button) 4WD transmission system, the 4WD controller does everything - commanding the electromechanical transmission mode shifting mechanisms in the transfer box, commanding the vacuum system for the (dis)engagement of the front wheel hub heads, informing the ABS system, and (most importantly) deciding when and if to operate the transfer box.
+* In the newer (push-button) 4WD transmission system, the 4WD controller does everything - commanding the electro-mechanical transmission mode shifting mechanisms in the transfer box, commanding the vacuum system for the (dis)engagement of the front wheel hub heads, informing the ABS system, and (most importantly) deciding when and if to operate the transfer box.
 * The driver just invokes the 4WD controller by pressing one of the buttons, and then can only sit and watch.
 * The 4WD controller checks a number of inputs / conditions before it will change the transmission mode, and these can all contribute to it not working.
@@ Line 226: / Line 229: @@
 # The actuator moves the mechanical bits in the transfer box, connecting the front propeller shaft to the transfer box.
 # A dedicated sensor in the transfer box informs the 4WD controller if the mechanical engagement in the transfer box has completed successfully.
-# If the 4WD controller detects that the actuator in the transfer box has completed the change successfully, then the 4WD controller changes the condition of the green 4WD light on the instrument panel from "off" to "flashing", and sends the signal to the vacuum system (valves and switches) to send the vacuum to the front wheel hub heads, in order to engage them.
+# If the 4WD controller detects that the actuator in the transfer box has completed the change successfully, then the 4WD controller changes the condition of the green 4WD light on the instrument panel from "OFF" to "flashing", and sends the signal to the vacuum system (valves and switches) to send the vacuum to the front wheel hub heads, in order to engage them.
-# The 4WD controller waits a bit to get a return signal from the vacuum system if the vacuum is achieved (this is officially considered an indication that the hub heads should have engaged).
+# The 4WD controller waits a bit to get a return signal from the vacuum system if the vacuum is achieved.
-# If the 4WD controller receives a return signal from the vacuum system before time-out, the 4WD controller changes the condition of the green 4WD light on the instrument panel from "flashing" to "ON" and also sends the signal to the ABS controller (another computer in the vehicle - if the vehicle has ABS) that 4WD transmission is engaged, so that the ABS controller can adjust the operation of the ABS system accordingly.
+#* A signal of successful vacuum formation is officially considered an indication that the hub heads should have engaged.
 # The process of shifting the transmission from 2WD to 4WD-H is formally complete.
@@ Line 236: / Line 240: @@
 If the 4WD controller does not receive a positive signal from the transfer box in step 4 of the above process:
-# The 4WD controller will turn the green 4WD light to "on" just for a fraction of a second, and then leave it in the "off" state.
+# The 4WD controller will turn the green 4WD light to "ON" state just for a fraction of a second, and then leave it in the "OFF" state.
-# An audible click will be heard the the same time when the green 4WD light goes back to the "off" state.
+# An audible click will be heard the the same time when the green 4WD light goes back to the "OFF" state.
 # The 4WD controller will simultaneously command the actuator in the transfer box to return the bits inside back to "2WD" mode (front propeller shaft disengaged from the transfer box).
 # The 4WD controller will not even attempt to engage the vacuum system.
 * A simple cause can be a loose connector or broken wiring between the 4WD controller and the transfer box - check the wires and connectors under the car and around the transfer box.
@@ Line 250: / Line 253: @@
 If the 4WD controller does not receive the return signal from the vacuum system that the vacuum is successful (in step 6 in the above process):
 # The green 4WD light will remain in the "flashing" state, '''flashing twice per second''';
-# The 4WD controller will receive no signal about the engagement of 4WD operation;
+# The ABS controller will receive no signal about the engagement of 4WD operation;
 # The transfer box will still remain in 4WD mode, even after restarting the vehicle.
-# Pressing the 2WD button on the dash board (in order to cancel everything and return the transfer box back to 2WD operation mode) will have no effect - the 4WD controller will not do anything.
+# Pressing the 2WD button on the dash board (in order to cancel everything and return the transfer box back to 2WD operation mode) will have '''no''' effect - the 4WD controller will not do anything.
 # The system will effectively be permanently "stuck" in the state where the transfer box is in 4WD mode (front propeller shaft connected to it), the front wheel hubs not being engaged, and the green 4WD light flashing.
 # This situation will remain even after restarting the vehicle and pressing the 2WD button afterwards - the 4WD controller will just keep on trying to finish the 4WD engagement process once immediately after every vehicle restart, and will sit idle for the remainder of the vehicle run, ignoring any button presses.
@@ Line 260: / Line 263: @@
 To "fake" the signal to convince the controller it is in 4WD, look under the battery tray where you will see two valves (VSV1 and VSV2). UNDERNEATH these is a vacuum sensor with a white connector and two wires. Short out the connector with a bit of wire to make the controller think the sensor has operated. This fakes that the vacuum is good and the 4WD system will complete its cycles ok.
 ==== Exception - Internal transfer box actuator and position sensor ====
 The transfer box can also get "stuck" in 4WD if one of the internal sensors to the transfer box fails. The 4WD controller reports this by '''rapidly flashing the 4WD light (5 times per second)'''
@@ Line 270: / Line 275: @@
 . Unbolt the actuator, inspect it and manually operate it checking that it moves.
 . If this does not cure it then the cheapest way is to replace the transfer box as its cheaper than getting the parts.
 === Example when shifting from 4WD-H to 4WD-L ===

@@ Line 64: / Line 64: @@
 [[File:Manually operated wheel hub head on a wheel - A01.jpg|thumb|left|400px|Manually operated free-wheeling wheel hub head - the black thing in the middle of the wheel]]
-* Most vehicles with part-time 4WD transmission (like the Jimny) have (un)lockable free wheeling front wheel hub heads / caps, which can (dis)connect the road wheel hub assembly from/to the transmission (the CV joint).
+* Most vehicles with part-time 4WD transmission (like the Jimny) have (un)lockable free wheeling front wheel hub heads / caps, which can (dis)connect the road wheel hub assembly from / to the transmission (the CV joint).
 * The hubs heads / caps sit on the ends of the axle - they visibly stick through the hole in the center of the wheel.
-* With them unlocked, the wheels are free to rotate on their own, without turning all the bits and pieces in the (front) axle - that's the "free wheeling" part of the name!
+* With them unlocked, the wheels are free to rotate on their own, without turning all the bits and pieces in the (front) axle (and vice versa) - that's the "free wheeling" part of the name!
 * This saves fuel, saves on mechanical wear of the disconnected components and improves performance when the vehicle is in 2WD (RWD) transmission mode, as it is pointless to turn a lot of gears and metal if they are not required.
-* However, in 4WD transmission mode, the hub heads lock the wheels to the drive shafts in order to let the engine turn the wheels.
+* However, in 4WD transmission mode, the hub heads need to lock the wheels to the drive shafts in order to let the engine turn the wheels.
-* There are three operational types of free wheeling hub heads - manually operated, pneumatically operated and automatically (un)locking.
+<br clear="all">
-* Jimnys have pneumatic (vacuum) (un)locking free wheeling front wheel hub heads / caps.
@@ Line 77: / Line 92: @@
 * And they generally don't bring bad nor good luck!
 * On the other hand, if you paint them to look sexy, they might attract some females (depending on the species - wolf, bear, snake, skunk, etc.).
@@ Line 97: / Line 111: @@
 # Unlike most automatic free wheeling hub heads, vacuum operated free wheeling hub heads can (dis)engage "''in situ''" - without requiring that the vehicle/wheel makes at least one full wheel turn during the (dis)engagement process.
 #* This attribute makes vital difference if 4WD engagement is about to be performed after the vehicle had already got stuck in 2WD.

@@ Line 43: / Line 43: @@
 Jimny's 4WD system consists of two ''physically unrelated'' subsystems:
 # Pneumatic (vacuum) system for (dis)engaging the free wheeling front wheel hub heads;
 # Transfer box with its embedded status sensors + wiring, and with a mechanical selection lever (in the older design) or with a electro-mechanical actuators (in the newer design).
-These two subsystems are then functionally joined/operated together by a dedicated computer called the 4WD controller, so they all together functionally form the 4WD transmission system.
+These two subsystems are then functionally joined / operated together by a dedicated computer called the 4WD controller, so they all together functionally form the 4WD transmission system.

@@ Line 23: / Line 23: @@
-First of all, there are some rare "el cheapo" Jimnys 3 (mostly from early year 1998-2001) which have no 4WD transmission mechanics - they are 2WD (RWD) only. This article is not for them.
+First of all, there are some rare "el cheapo" Jimnys 3 (mostly from early year 1998-2001) which have no 4WD transmission mechanics - they are [https://en.wikipedia.org/wiki/Rear-wheel_drive RWD 2WD] (real wheel drive two wheel drive) only. This article is not for them.
 '''All''' Jimnys 3 with 4WD transmission have the '''same''' overall transmission design:
-* User selectable [https://en.wikipedia.org/wiki/Four-wheel_drive#Part-time part-time] 4WD transmission which defaults to [https://en.wikipedia.org/wiki/Rear-wheel_drive RWD 2WD] (real wheel drive two wheel drive) mode.
+* User selectable [https://en.wikipedia.org/wiki/Four-wheel_drive#Part-time part-time] [https://en.wikipedia.org/wiki/Four-wheel_drive 4WD] [https://en.wikipedia.org/wiki/Transmission_(mechanics) transmission] which defaults to [https://en.wikipedia.org/wiki/Rear-wheel_drive RWD 2WD] (real wheel drive two wheel drive) mode.
-* Dedicated transmission box / transfer case (separate unit from the gear box) with the following characteristics:
+* Dedicated [https://en.wikipedia.org/wiki/Transfer_case transmission box / transfer case] (separate unit from the gear box) with the following characteristics:
-** User selectable high & low (reduction) range gear set;
+** User selectable high & low (reduction) range [https://en.wikipedia.org/wiki/Gear_train gear set];
-** With (dis)engagement mechanism for the front propeller shaft;
+** With (dis)engagement mechanism for the front [https://en.wikipedia.org/wiki/Drive_shaft propeller shaft];
-** Without center (inter-axle) differential;
+** Without center (inter-axle) [https://en.wikipedia.org/wiki/Differential_(mechanical_device) differential];
 * [https://en.wikipedia.org/wiki/Locking_hubs Free wheeling hub heads] on the front wheel hubs, pneumatically (vacuum) operated.

← Older revision		Revision as of 14:03, 4 March 2021
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	{{Gen3\|}}		{{Gen3\|}}

−	If you are having issues with the 4WD transmission system in your Jimny 3, the articles [[~~Vacuum hubs - checking and testing~~\|'''"~~Vacuum hubs - checking and testing~~"''']] and [[Manual or fixed front wheel hub heads\|'''"Manual or fixed front wheel hub heads"''']] might be of great assistance.	+	If you are having issues with the 4WD transmission system in your Jimny 3, the articles [[4WD transmission failure diagnostics\|'''"4WD transmission failure diagnostics"''']] and [[Manual or fixed front wheel hub heads\|'''"Manual or fixed front wheel hub heads"''']] might be of great assistance.