Sorry if this is slightly off topic but I've been wondering, what does the air activated free wheel mechanism do?

Think of it as a poor substitute for automatic locking "free wheeling" front hubs

From the factory, on these vehicles there are no freewheeling front hubs - there is a flange that connects the hub to the axle, and the two rotate together - the other end of the axle goes in to the differential side gears and that rotates also.

In 2WD, the air activated free wheel mechanism disconnects the differential from the ring gear - so the rotation stops at this point, the ring gear, pinion and front driveshaft, etc do not rotate.

When you shift to 4WD, you engage a drive hub in the transfer case, so that power is transmitted through the front drive shaft to the front axle, and a switch on the transfer case turns on an air pump (through a controller), which activates the free wheel mechanism, causing it to lock the differntial to the ring gear, so that power will reach the front axles, and then the front wheels.

This is a part of what Suzuki calls "Drive Select", perhaps more commonly known as "SOTF" or Shift On The Fly, which allows you to shift between 2HI and 4HI without stopping the vehicle - provided that you meet certain conditions, speed must be less than 60 mph, wheels must be straight ahead, etc.

Basically there are two types of axles in these trucks.

The original front wheels drive diff was essentially all gear mesh.  In order to engage the front differential, you had to hop out and turn your manual locking hubs on both sides of the front axle from "Free" to "Locked" and then engage the 4WD shifter in the cab into either 4Hi or 4 Lo, then go.  A pretty bullet proof design... but required more "effort" from the operator.  If your hubs aren't locked, your CV axleswon't drive the tires.  if you aren't in 4WD, the tires roll but the axles are stationary.

With the (newer) air actuated front ends, the front hubs are permanently "locked" because the the front hubs are "fixed" and grip the front splines of the drive shafts (CVs) all the time.  When you engage your 4WD shifter you "turn-on" the front actuator pump which starts pumping air to the front actuator (which is built into the front diff) and this air pressure inflates a diaphragm which pushes cogs into the differential gears to provide you with your front drive to the axle/s.  Because these hubs are always locked, the CVs also continually rotate with the tires as well which causes additional wear on the front axle seals as well.  So IF the air pump fails (or you develop another air leak, etc) you are quickly reduced to a 2WD truck.

The reason for the change.... was probably the simple fact manufacturing is more and more moving towards providing "comfort" and "ease of use" to the consumer.  If this trend continues at some point our arms and legs will turn into useless appendages without function, but it probably won't matter because we'll all be so damned obese we won't be able to walk anyway.

Fordem, we typed a reply at the same time.  I have more sarcasm in mine, though and I also think the front CVs are spinning all the time because they can't disengage from the Cvs because of the locked spline.

Fordem, we typed a reply at the same time.  I have more sarcasm in mine, though and I also think the front CVs are spinning all the time because they can't disengage from the Cvs because of the locked spline.

No sweat man - I'm not separating the CVs from the axle for the purpose of the explanation, and you are 100% correct, they do spin all of the time.

I don't quite agree on the reason for change - but - like you, I'm just guessing, and my guess is it had to do with increased competition in the compact SUV arena, and since the competition (Rav 4 and CRV's) were AWD and completely transparent to the driver, this was Suzuki's first step in that direction.

Take a look at the time line - from a lever shifted transfer case with SOTF, they went to an electrically shifted transfer case with SOTF, and then full time 4WD with an electrically operated locking center differential and low range.

I'm with ya!

Cool, thanks guys!  The CV's do spin in 2wd, but they sell manually locking hubs.  I'm got them with the Calmini lift, I'm gunna install them on mine soon, save my bearings alittle wear.

It connects/disconnects the front axles from the front prop shaft - same result as freewheeling hub units.  The idea is that when you are in 2WD, you don't want the wear and drag of the wheels rotating the front prop shaft and diff.

http://s305.photobucket.com/albums/nn204/jayinbarrie/Decorated%20images/?action=view&current=DSC02470.jpg&newest=1
I was lucky I just broke the ear mount.  Made a new bracket that's much more secure.  There's a nice write up somewhere here for the Sidekick on beefing up the bracket.
Was a rocky area where it happened.  Not sure what gear I was in.

Quote from: Minion33088 on April 13, 2010, 08:27:17 PM

Sorry if this is slightly off topic but I've been wondering, what does the air activated free wheel mechanism do?

....When you shift to 4WD, you engage a drive hub in the transfer case, so that power is transmitted through the front drive shaft to the front axle, and a switch on the transfer case turns on an air pump (through a controller), which activates the free wheel mechanism, causing it to lock the differntial to the ring gear, so that power will reach the front axles, and then the front wheels.

It's a system that Suzuki refers to as "SOTF" or Shift On The Fly, which allows you to shift between 2HI and 4HI without stopping the vehicle - provided that you meet certain conditions, speed must be less than 60 mph, wheels must be straight ahead, etc.

Are you sure SOTF is a Suzuki term?

The reason I doubt it is that the pneumatic mechanism is not specifically SOTF.  You can SOTF just as well with the Gen 1 setup, which uses manual or auto freewheel hubs.  The only real difference to SOTF between Gen 1 and Gen 2 is that the Gen 2 Transfer Case has synchro for enagaging the front drive in High Range.  However, I have vehicles of both generations, and I find no difference in using SOTF.

If I recall correctly the term appears in the Gen2 owner's manual - I'm too lazy to go out to the car to check - but if I'll try to remember to check it when I go out later.

I do believe that the pneumatic setup IS solely to allow SOTF and I will attempt to explain why - I would also point out that, this is just my opinion, and should not be taken as a statement of Suzuki's intent.

Since you have both generation vehicles, and presumably easy access to both owners manuals, I will ask you to check your Gen1 manual - I believe you'll find it contains a recommendation that you bring a vehicle equipped with auto hubs to a complete stop before shifting from 2HI to 4HI, for one transmission type (auto or manual, I don't remember which) and you will also find that it instructs you to stop and reverse after shifting from 4HI to 2HI to unlock the hubs. (For me, getting access to a Gen1 owner's manual means going over to my sister to borrow hers, and as I explained earlier, I lack the motivation to do anything on this sunny Saturday morning.)

At this point it should be quite clear that manual hubs or automatic hubs, a Gen1 requires you to stop the vehicle and either get out to lock/unlock the hubs, or stop and backup - putting an end to any discussion on shifting on the fly.

Check your Gen2 manual now - I believe you'll find it allows shifting from 2HI to 4HI and back, without stopping at speeds of up to 60 mph, provided the front wheels are in a straight ahead position - if the vehicle had either manual or auto hubs - you would be required to stop (just as you are with a Gen1), so Suzuki had to find a way to engage the front hubs that did not require stopping - presto - the air activated (pneumatic) free wheel disconnect.

And for what it's worth - I do recognize that with manual hubs you can, provided you remembered to lock the hubs in advance (assuming that you knew in advance you were going to use 4WD) shift from 2HI to 4Hi and back, making the key change that enables shift on the fly the sychro in the transfer case - however - shift on the fly would not have been possible without some form of automatic freewheel mechanism that did not require bringing the vehicle to a stop.

YV/MV

Are you sure SOTF is a Suzuki term?

You're quite correct - the owner's manual calls it "Drive Select" - however, a quick google search will find you plenty of reviews that refer to it as shift-on-the-fly - I have corrected the earlier post, thanks for the heads up.

The X-90 has auto hubs, and I do have to lock (or engage) the hubs by selecting 4H when stationary, then driving off.  However, once I have done that, I can shift between 4H and 2H (and vice versa) on the move - the action is quite smooth.

Now, the vexed question of the Gen1 Owners Manual.  In one place (Page 6-9 in my copy) it does say that, if you have auto hubs, stop when shifting between 2H and 4H.  But on Page 5-5 it says that once the auto hubs are locked you can shift 2H>4H>2H on the move, provided the steering is straight ahead.  And you can.

I've written to Suzuki GB to point out this conflict, and asked them whether page 6-9 needs some amendment.  The reply: "please ask your dealer, who is expert in operating Suzukis".  Yeah, right....

The Drive Select is a great convenience - I love it (and I particularly like how easy it was to modify to get a 2WDLo facility), but it does sound as if it results in lower reliability.

The only comment I'm going to make at this stage is this ...

With the auto hubs, once you lock them, they're locked until you come to a stop and reverse - with the pneumatic disconnect, it'll unlock about 10 seconds after you shift into 2HI.

One disconnects completely, and the other doesn't

i snapped the front drivers side mounting bracket last weekend, made some funny noises in 4x4 when it happened on a rocky hill..  replaced the bracket with another aluminum and internal parts seems to be ok...  POS but i'm glad the bracket let go instead of the diff housing.

Wow, lucky! What were you doing when it broke?

I just got my xl7 steel front third and now I just need the sidekick rear third (for a decent price). As far as I know I can't just swap in the rear pig so I need to swap the entire axle. I wasn't going to change the gears for the bigger tires but now I'm doing it anyways since i want to get rid of the aluminum housing. I guess it was going to happen one way or another! Should be a sweet improvement all around as long as the everything fits lol.