Restrictions when towing a Jimny - technical explanations

Suzuki's Owner's manual for Jimnys has a section 7 about loading and towing a vehicle.

That chapter contains several severe warnings on how not to tow a Jimny, promising critical damage to the transmission if done the wrong way.

In short, it says that the rear wheels must not have contact with the ground when a Jimny is being towed no matter what.

It also says that the front wheels can have contact with the ground when a Jimny is being towed (from behind), but only if the gear box is in neutral and if both front wheel hub heads are unlocked.


I wrote a corresponding subchapter in the BigJimny wiki article " DO's and DONT's with Jimnys " based on that official Suzuki chapter.


Now,

I can understand why the front wheel hub heads have to be unlocked, in order to prevent transmission wind up during motion.
I am just not certain if having a front propeller shaft connected to the transfer box mechanisms (with the front hub heads being unlocked) would pose an issue here. In theory, any motion of the front propeller shaft during vehicle's motion should be "soaked" by the front differential in this case with much issues.


However, what I definitely don't understand is why is it strictly prohibited to have the rear wheels on the ground when the vehicle is being towed, even if the front wheels are not in contact with the ground?

Ok . So if you tow a Jimny with the front suspended ie rear wheels down it causes amongst other things a lack of lubrication of the gear boxes especially as the vehicle is not level there's only minimal splash lubrication because the transmission is in neutral and the input shaft is not being turned so the oil pump isn't working. . On the front having the propshaft connected makes no difference if the hubs are disengaged.

It is a bit misleading in that towing the car with a rigid towbar system with all wheels on the road is OK as long as the front hubs are unlocked.

11/60,
thank you for a proper explanation.
But it still leaves some questions non-addressed for me.


So the only issue is the lubrication of the gears in the gear box?
I suppose that the lubrication of the transfer box would not be an issue in this situation, would it?

Regarding the oil pump, I suppose that you refer to engine's oil pump. But I do not see what is an issue if that oil pump is not working, since the engine is turned off anyway and the gear box is in neutral, meaning that nothing turns in the engine during towing anyway.

As far as I know, during normal operation, the oil in a manual gear box circulates only by the splashing effects of the gears, not by the operation of any oil pump. Or am I wrong? If I am correct, then I do not see much difference (regarding lubicration of the gears in the gear box) between running a gearbox by engine's throttle or running it in neutral mode with the vehicle cruising in "freewheeling" mode. The gears are turning anyway, its just the source of the force which turns them that changes (engine or the wheels).


If I am correct, shifting the gearbox in neutral while the engine is running and the vehicle being in motion, and then freewheeling on a flat road or downhill would essentially be the same situation as towing that vehicle with its engine being turned off, gearbox in neutral and (at least) its rear wheels on the ground.

If the latter is bad for the gear box, then so should be the first too (freewheeling with the engine on and gearbox in neutral), as some people have a habit of doing?



mickt,

Suzuki did not write that towing a Jimny with all wheels on the road and front wheel hub heads disconnected is allowed, and neither did I in the above mentioned wiki article.
It is clearly stated that the rear wheels must not have contact with the ground during towing no matter what, implying then that all four wheels on the ground is also prohibited.

What is officially allowed though, is to have ONLY the front wheels on the ground, but only after making certain that both front wheel hub heads are disconnected.

I was under the impression that the gearbox has a separate oil pump driven by the input shaft. I could be wrong.

I'm not an expert on Suzuki but in general automotive terms a manual gearbox is splash lubricated whilst an auto box relies on the input shaft oil pump. An auto should never be towed, or even bump started as it will not be lubricated. I don't understand why Suzuki say not to tow a manual, unless it risks damage to the transfer box.