2WD-L transmission mode

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Introduction

• Jimny has part-time four wheel drive transmission system.
• That means that the engine nominally drives only the rear axle (rear wheel drive).
• Since only two wheels are driven, that is called "2WD" mode.

• The driver can manually engage "4WD(-H)" mode.
• In that mode, the front drive train (propeller shaft, differential, half axles, etc.) and the front wheels get connected to the transmission as well.
• When this is accomplished, both axles receive the equal amount of torque ("power") from the engine, and consequently all four wheels receive engine power.

Constraints of 4WD and 4WD-L modes

• However, because the transfer box contains no center differential, the front and rear propeller shaft always have to rotate at the same speed in 4WD mode.
• This in practice means that Jimny must not be used on non-slippery surfaces when in 4WD mode (except for very short distances and ONLY going dead straight).
• Otherwise, the transmission can be severely damaged!

• If steering to left or right must be done while Jimny is in 4WD mode, the road surface must be very slippery for the transmission to be able to relieve the tension caused by the lack of center differential.
• Wet tarmac roads are typically not slippery enough for 4WD, nor are hard gravel and dirt roads, nor dry grass fields.

• Now, Jimny also has low range gears, meaning that it can effectively halve all of its gears' speed while doubling the torque.
• That functionality is essential for any serious all terrain duty, and very helpful even on gravel roads of varying constitution.

• However, Jimny's transmission controls (both older lever-style mechanically operated and newer push-button-style electrically operated) allow the low range to be engaged only in conjunction with 4WD mode.
• Therefore, Jimny allows only "4WD-L" mode to be used.
• This means that low range mode is always severely constrained by the above mentioned disadvantages of ordinary (high range) 4WD mode.

A side note:

• In all Jimnys with lever style operated transfer boxes, as well as in all earlier Jimnys (2005-2008) with push push button style operated transfer boxes, it is not possible to shift directly from 2WD-H to 4WD-L and vice versa.
• In order to shift from 2WD-H to 4WD-L or vice versa, the transmission must first be manually shifted into 4WD-H.
• However, on push-button operated Jimnys made after 2008 (factory "type 7" and newer), the 4WD controller allows shifting "directly" from 2WD-H to 4WD-L and vice versa.
• Actually, it does not shift directly - the same process of going through 4WD-H mode happens, just automatically by the 4WD controller instead by the operator.

Reasons for having 2WD-L mode

• On the other hand, in practice there can be several situations where "2WD-L" mode would be desired - using low range gears without 4WD mode.
• In that mode, steering would be safe to do on any kind of surface.

• Typical situation is when driving on a dry, rough, twisty gravel or rocky road.
• On such roads, steering is applied a lot, the road surface is difficult, so 1st low gear or 3rd low gear are required, but the road surface is not slippery.
• Using 2WD-L mode in such a situation would be ideal.

• Another useful situation for 2WD-L mode would be to tow a trailer for some short twisty distance, or to make an easier start with a trailer when going uphill.
• Also, parking in and out of difficult (sloped) (and wet) parking positions would be much easier with 2WD-L mode.

Possibilities of having 2WD-L mode

So, how to "enable" 2WD-L mode?

• If you have already changed your factory vacuum operated free wheeling hub heads on the front wheels to manually operated ones, engaging 2WD-L mode for you is trivial.
• Just do not engage the front wheel hub heads, and then shift the transmission into 4WD-L - it will effectively work in 2WD-L mode.

• Technically, 2WD-L mode can work in Jimny's transmission system.
• The preconditions for entering it are fulfilled by simply not connecting the front propeller shaft to the transfer box and/or not engaging the front wheel hub heads.
• However, it is always "simpler said than done".
• This can be done manually by removing the front propeller shaft and/or blocking or disabling the vacuum system for the front wheel hubs.
• However, both 4WD modes would be permanently lost (until everything is returned back).

• Suzuki could have simply made the 2WD-L mode possible by making another "position / program" in Jimny's transfer box lever (in older Jimnys) or in the 4WD controller (in newer Jimnys).
• In that position / program, the lever / controller would only operate the low range selector in the transfer box, and leave the front propeller shaft and the front wheel hubs disconnected.
• But Suzuki did not, either because of lack of thought or because some smart slick manager thought that adding one more transmission mode would confuse a typical user.

• So, the question is how to add/enable the 2WD-L mode "systematically" - to be selectable at any time from the cabin and to be compatible with the 4WD controller and all the mechanicals.

• The solution depends if the Jimny has older stick-style mechanically operated transfer case, or newer push-button-style electrically operated transfer case.

Solutions for older lever-operated transmission system

Solution 1 - installation of a custom "2WD-L" switch

• The solution for Jimnys with this 4WD transmission system is to install a custom switch in the cabin, and wire it to a blue/black wire going from the 4WD controller to the transfer box.
• The purpose of the switch is to selectively cut-out the feedback signal from the 4WD mechanism engagement sensor in the transfer box to the 4WD controller.

• This way, whenever the switch is OFF, the transfer box can be operated with the lever without the 4WD controller being aware of that.
• In other words, while the switch is OFF, the 4WD controller will think that the transfer box is in ordinary 2WD mode, no matter in which mode it really is.
• Consequently, as long as the switch is in the OFF position, the 4WD controller will not engage the front wheel hub heads by operating the vacuum system.

• The switch can be operated from OFF to ON position or vice versa even while the transfer box lever is already in 4WD-H or 4WD-L mode.
• In this case, you are effectively simulating the shift of the transfer box between 2WD<->4WD to the 4WD controller whenever you flip the switch without doing anything to the transfer box.
• This means that, while the transfer box really is in 4WD-H or 4WD-L mode, the 4WD controller will engage the front wheel hub heads whenever the switch is turned to ON position (normal 4WD) and disengage them whenever the switch is turned to OFF position (providing effectively a 2WD-L mode in a supposed 4WD-L mode).

• Whenever the switch is in the OFF position, the green 4WD light on the instrument panel will also be in the OFF state (as the 4WD controller will believe that the transfer box is in ordinary 2WD mode), no matter in which mode the transfer box is.
• Therefore, with the switch in the OFF position, your only indication of the current transmission mode of the vehicle is the physical position of the transfer box lever.

The video

Here is a (poorly) made video of the simple process of installing the switch:

• Credits go to the site owner "Mlines" for making the video!

Solution 2 - replacing vacuum hub heads with manual hub heads

• In Jimnys with lever operated transmission system, 2WD-L transmission mode gets enabled indirectly (as a side-consequence) when original vacuum operated front wheel hub heads are replaced with manually operated front wheel hub heads.

Explanation:

• With manually operated front wheel hub heads, just keep the hub heads disengaged and shift the transmission lever into 4WD-L mode.
• Since the front wheels are still disengaged, the transmission will effectively operate in 2WD-L transmission mode, just like it would with the solution 1 (custom "2WD-L" switch).

Read the wiki article "Manual or fixed front wheel hub heads" for all the details on converting to manual wheel hub heads.

Solutions for newer button-operated transmission system

Needs to be investigated and written here ...'

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Page last edited on 20/11/2017 by user Bosanek