# Towing an Iltis



## bobdown (10 Dec 2005)

Does anybody know the proper way to tow an Iltis?

I have bought an Iltis for running around in the bush with my kids, but would like to be able to tow it with a tow bar on all 4 wheels.  I want to know if anyone knows if this would be recommended, and if so what would be the best way to do so?
Leave it in 4WD or 2WD? and ....


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## WogCpl (10 Dec 2005)

place her in 2WD, make sure the diff locks are off, and the transmission is in neutral and you should be just fine, if you have any doubts remove the rear drive shaft while towing. When placed in 2wd, the iltis is rwd only.


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## bobdown (10 Dec 2005)

Thanks for your help!
B


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## GO!!! (10 Dec 2005)

Return to wherever you got the Iltis, and try to get your hands on an "A" frame, these hook up in 10 mins or less, and are the ideal solution for towing. They attach directly to the towing shackles on the front of the bumper, and the towed vehicle is under your complete control.


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## gdict (3 Jan 2006)

I agree that if you tow the Iltis on all fours, you should put it in 2WD with diffs unlocked and tow away. For that matter, you should drive the Iltis in 2WD all the time unless you are off road and need 4WD. For some strange reason DND decided that the Iltis should be drive in 4WD all the time. This makes no sense. Even the Bundeswehr manuals say that 4WD should only be used in of road conditions. When in 4WD, the drive train is FULLY LOCKED front to rear with no differential action. This can cause binding between front to rear when drinving on firm surfaces. Maybe this is why CDN Iltis are so trashed. Even the supposed 'experts' have no idea about the simple mechanics of the Iltis.

Now, back to the towing question, if you believe it is OK to drive the Iltis in 4WD all the time, then it is OK to tow it in 4WD. All the same parts are spinning, the only difference if wether the front and rear drives are linked. My opinion though is that the Iltis should be in 2WD ALL OF THE TIME, unless off road. 

There should be no need to pull the driveshaft since manual transmissions do not suffer from the same lubrication problems as automatics when the output is spinning, but not the input shaft. You might get better mileage with the shaft out, but the PITA factor would outweigh any slight savings. 

On the subject of the drive shaft, if you ever find yourself with a bent driveshaft you can simply remove it and the Iltis will drive just fine with the '4WD' engaged. It essentially becomes a FWD. The driveshaft is pretty exposed, so it is very realistic to expect that it could get bent in some extreme offroad adventures.

Cheers!

Greg


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## George Wallace (3 Jan 2006)

Welcome to Army.ca

That being said; where did you come up with this info?





			
				gdict said:
			
		

> ...... For some strange reason DND decided that the Iltis should be drive in 4WD all the time.


In all my years with the Iltis, I always drove in two wheel drive, using 4 WD only when necessary.  It was both for fuel economy and better performance of the vehicle.  Hwy Driving Speeds are too high for 4 WD.  Obviously your statement above is false.

If you are going to post information, please insure that you post correct information.


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## DG-41 (3 Jan 2006)

> Even the supposed 'experts' have no idea about the simple mechanics of the Iltis.



Well, I was a maintainer in my former life, and I wrenched on many an Iltis. I also been the driver/engineer for a 4WD race car for the last 8 years or so - see http://farnorthracing.com . 

Let's talk about differentials:

When a vehicle goes around a corner, the inside wheels make a smaller radius turn than the outside wheels. Accordingly, the outside wheels travel a larger distance, and must turn faster than the inside wheels. If the wheels are locked across the car by a solid axle, the inside wheel will break loose and spin when negotiating a corner.

To get around this problem, there is a gearing mechanism called a differential, so-called because it allows the wheels to turn at different speeds while still maintaining drive to each one. Install a differential and you get rid of the inside wheelspin problem.

However, you induce a new problem: as a direct consequence of the way the differential mechanism functions, the faster-moving wheel gets more power in direct proportion to the relative speed of the wheels. If you are placed in a situation where one wheel of a pair connected by a differential is moving very quickly relative to the other, 100% of the power will go to the faster-moving wheel. If one wheel is in a low-traction situation (like resting on ice, or raised up in the air) it, not the wheel with the grip, will get the power.

Now consider a 4WD vehicle. The power comes out of the engine, is split front and rear via the centre differential, and then each output from the centre diff (sometimes called the transfer case) also gets a differential to handle the spilt side to side. So you have three spots for diffs on an AWD - front, centre, and rear.

Now, if those diffs are just plain old differentials, that means that if any ONE wheel loses traction, the whole vehicle loses drive and you don't go anywhere. For a cross-country vehicle especially, this is sub-optimal. Put one wheel in the air or on something slippery, and you stop moving.

At the very least, you need some mechanism to lock the centre slot so that power loss on one end of the vehicle doesn't bleed off the power going to the other end. On the race car, we had a very sophisticated combination of a Torsen torque-biasing mechanism and a silicone viscous coupling that attempted selectively lock the centre diff according to the instantanious grip availible to the car. The Iltis, being far cheaper and simpler, simply keeps the centre slot locked all the time.

Note, however, that this causes no detriment to the performance of the vehicle! When the centre slot is locked, the power distribution is fixed at 50/50 front/rear. On a race car, this tends to cause understeer when driven at the limit, especially if the car has a lot of power. On a 60 HP Iltis not driven in competition, totally not an issue. On an Iltis, the only downside to being in 4WD is the extra friction and inertia in the rear differential and rear output shafts consuming a little extra power and hurting the gas milage a little bit.

An Iltis in 2WD mode is FWD only, BTW.

Now in the race car, we have similar Torsen diffs in the front and rear slots to try and maximise power put to the ground at all times. The Iltis has a manual rear diff lock (and it's possible on some Iltis that the diff lock locked the front diffs as well; I don't know if any Canadian Iltis got the dual-locker tranny or not. With the diff lock engaged, it would take both rear wheels spinning and one front wheel spinning to lose drive. With a dual-locker, all 4 wheels would have to be spinning to lose drive.

The downside to having the diff lock engaged is that you no longer have differential action on that axle, and you get inside wheelspin when going around corners. This is OK in soft stuff, but not on pavement.

So then, summing up:

1) The only downside to 4WD operation on pavement is reduced fuel economy and top speed.

2) Engage the diff lock on loose or slippery surfaces; disengage it for hard surfaces or pavement

3) Flat towing can be done in either FWD or 4WD mode. If lift towing, it is better to be in 2WD mode, but it isn't critical

4) The A-frame is your friend when flat-towing any SMP pattern vehicle.

DG


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## c_canuk (3 Jan 2006)

DG 

not that I want give the impression I know more than you, as I clearly know much less, but I was under the impression that with regular 4wd (no center diff or center diff locked) when cornering all 4 wheels want to spin at different speeds, and with the same rpms sent to front and back, one tire somewhere has to slip. and on hard dry pavement this is a problem?

have I been misled?

thanks


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## GO!!! (3 Jan 2006)

What about driveline tension - or does that only apply if the diffs are locked?


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## TN2IC (3 Jan 2006)

bobdown said:
			
		

> Does anybody know the proper way to tow an Iltis?
> 
> I have bought an Iltis for running around in the bush with my kids, but would like to be able to tow it with a tow bar on all 4 wheels.  I want to know if anyone knows if this would be recommended, and if so what would be the best way to do so?
> Leave it in 4WD or 2WD? and ....



To tow it? Netural is the best way.. so no gear pressure is applied to the drive train.

As for a A-Frame... they are good to get your hands on if you can...

Have Fun...

BTW...Most parts of the old VW Rabbit will fit on it..


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## WogCpl (3 Jan 2006)

Well, here we go. The Iltis is rear wheel drive if the 4wd is not selected!!!
First of all the Iltis was ment to be driven in 4wd or 2wd, it does not matter(2wd is more fuel efficent), but the default position according to the manual is the 4wd setting, the driveline is not fully locked in this positon, in order to fully lock the drive line you need to place the diff lock lever in the lock position. Since the differentials are locked by a seperate lever, you will still get differential action while cornering, until the differentials are locked then they will rotate as one solid axle, this is when you need to worry about axle "wind up". The only differential in the transaxle is the one for the front wheels, there is no "center diff" in an iltis and as a result when you select 4wd, you have locked the front with the rear, when you select "diff lock" you have locked left to right. The reason for pulling the rear drive shaft is really for towing long distances, it will be more fuel efficient for what ever the tractor may be, ie. an RV!
And the main reason for selecting 2wd(rwd) for towing, is to reduce wear through gear lash and allow the tractor to corner eaiser, anyone who has pushed an Iltis both in 2wd and 4wd knows that there is a huge difference.


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## WogCpl (3 Jan 2006)

Oh almost forgot, torque or "power" is always divided equally between the gripping wheel and the slipping wheel. RPM, however, is doubled in the "one wheel spinning, one wheel not" situation with a conventional differential.


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## c_canuk (4 Jan 2006)

so as long as the front and back diff are still open each wheel is free to spin at a different speed when the front and back driveshafts are recieving the same RPMs together from the transmission? Thats completely contrary to everything I've heard about 4WD operation vs AWD where there is a center diff.  ???


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## Haggis (4 Jan 2006)

TN2IC said:
			
		

> BTW...Most parts of the old VW Rabbit will fit on it..



The VW Fox's 1.8 L EFI engine is a good source of parts.  (Electric fans, too.)  Even sounds like an Iltis.

Personally I think it's easier to push than tow an Iltis.  To ensure your back doesn't get sore, make sure it's not too far to the cliff's edge  ;D


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## DG-41 (4 Jan 2006)

> so as long as the front and back diff are still open each wheel is free to spin at a different speed when the front and back driveshafts are recieving the same RPMs together from the transmission?



Depending on the amount of Ackerman in the steering geometry and the amount of steer angle, the difference in turning radius between front and rear wheels on the same side of the vehicle is very, very small - small enough to make no real difference and so not require a differential. You might see a little binding at slow speeds and extreme steer angles (like when parking), but in most cases, it's not really an issue.

At speed and on pavement, steering and cornering is less about the mechanical steer angle than it is about the slip angle of the tire... but now we are getting into hardcore vehicle dynamics and that's just not a topic for this board. Go visit http://streetmodified.org/books.html and do some reading. 

But that is not the case left/right. Lock the front and rear diffs on a 4WD/AWD, and it'll hop and chirp with any signifigant steer angle. The old 5/4 would do this.



> Oh almost forgot, torque or "power" is always divided equally between the gripping wheel and the slipping wheel.



Go park a non-limited-slip 2WD with one drive wheel on dry pavement and one drive wheel on wet ice, and see where you go....

DG


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## WogCpl (4 Jan 2006)

Go park a non-limited-slip 2WD with one drive wheel on dry pavement and one drive wheel on wet ice, and see where you go....

DG
  
[/quote]
Precisely, the torque being applied is only enough to brake the slipping wheel loose. The wheel that is stationary is getting the exact same amount of torque, but it is not enough to turn it on the traction surface, therefore the slipping wheel spins and the staionary wheel does not, if say 10 ft lbs of torque were applied to both wheels equally then torque would take the path of least resistance, (the spinning wheel) first, but not effect the stationary one. as power is applied the spinning wheel through differential action, spins faster (twice wheel speed if both had traction)  but torque remains contsant.


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## WogCpl (4 Jan 2006)

c_canuk said:
			
		

> so as long as the front and back diff are still open each wheel is free to spin at a different speed when the front and back driveshafts are recieving the same RPMs together from the transmission? Thats completely contrary to everything I've heard about 4WD operation vs AWD where there is a center diff.  ???



This is actually true however, the combined rpm's of the front wheels will match the combined rpm's of the rear wheels. Therefore each axle is receiving the same rpm from the driveshafts.


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## TN2IC (4 Jan 2006)

Okay... my head hurts.. stop it...


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## WogCpl (4 Jan 2006)

Sorry ;D i think Haggis's suggestion is the only way to get an iltis to break 120.


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