[deonengel]

Thanks Cats. When are you comming to have alook at the Caravan?

hi you guys, i am in the process of buying a gen 3 3.2 manual.
i am currently towing with a kb 320 @ 5 km/l - yes really
i allways towed in 4th - will this rule apply to the pajero as well??
i also read that 4wd h - is better for towing
i do not really do bundu bashing, but i sometimes get mommy's nerves (and mouth) going
any feedback will help me greatly - thanks you guys.
and ohhh yes - i had a long and very hard look @ everything else...
that's why id decided on the gen 3
regards

[4ePikanini]

Thanks Cats. When are you comming to have alook at the Caravan?

hi you guys, i am in the process of buying a gen 3 3.2 manual.
i am currently towing with a kb 320 @ 5 km/l - yes really
i allways towed in 4th - will this rule apply to the pajero as well??
i also read that 4wd h - is better for towing
i do not really do bundu bashing, but i sometimes get mommy's nerves (and mouth) going
any feedback will help me greatly - thanks you guys.
and ohhh yes - i had a long and very hard look @ everything else...
that's why id decided on the gen 3
regards

Can you not get an auto? They are great for towing!

Other than that.....yes, use 4th as far as possible and use 4H.

[CATS]

I know about the 4th gear towing being better for the box etc, but I can just not get myself to potter along with the revs running that high, maybe it is the speed at which I normally tow, between 100 and 120km/h, but I always engage 5th gear when the engine can handle it and drop down when the revs drop.

I had to replace the 1 and 3rd gear fork and the clutch retaing plate at around 220 000km, which I think is fair going given that I tow often and use it off road, but 5th gear is still good, so I don't know if I will change my driving style. For me 5th is definately used while towing.

I sometimes engage 4h when on slippery wet roads or mountain passes, but ussualy stay in 2h when towing.

Congrats on the Pajero, it really is a great vehicle. With my combinantion and all the extras like roofrack fitted etc, I get average 6.5km/l when towing at an average of 110km/h.

CATS

[bossieKar]

My 3.2did manual has done its fair share of towing horse boxes, odd Conquerer trailer and just recently a 1ton + loaded trailer from Pilansberg to Jhb and I was again amazed at the ease of the engine, 100-120km/h in 5th, coasting on cruize control, no strain at all, if I wanted to accelerate past a slower vehicle, no questions asked.
Past Harties up the long hills past Lesedi Cultural Village, used 4th and cruize control kept 90km/h, and still so easy.
Even slowing down to 60 for slower cars, resuming back to 90 was effortless.
Brakes on the vehicle is excellent when bringing a heavy load to a hault.

I really enjoy towing with this shorty.

[Bigwill]

Changing down to fourth only helps you to keep the engine revs within the power band. You do that to save the engine and allow the engine to produce more power. The transmission remains loaded with the same load (ie the caravan and the car's own weight) and therefore it does not help the transmission in any way. So stay in fith if your revs are above 1800rpm or there about. Else you waste fuel, cause heat generation and wear and tear on the motor etc. Just don't let the engine labour.

[Biggish]

Hi Bigwill,

Sorry, but I have to disagree with that advice.

It is a well know fact that towing in fifth gear at low revs increases EGT's, increases fuel consumption, introduces high levels of torsional vibrations and adds more stress to the gearbox and the engine. Just because the engine has sufficient torque to pull at such low revs doesn't mean it should. Mechanically speaking, everything would be much "happier" at slightly higher revs - certainly above torque peak.

My 2c,
Bruce

[4ePikanini]

Changing down to fourth only helps you to keep the engine revs within the power band. You do that to save the engine and allow the engine to produce more power. The transmission remains loaded with the same load (ie the caravan and the car's own weight) and therefore it does not help the transmission in any way. So stay in fith if your revs are above 1800rpm or there about. Else you waste fuel, cause heat generation and wear and tear on the motor etc. Just don't let the engine labour.

I beg to differ. In lower gears the amount of torque per timeframe is transferred over more cogs so less stress

Ie. If you use an electric motor with torque reduction gears you can move more weight at lower speed at less stress to the motor. If you use high torque direct drive you will lose speed/momentum and the motor works much harder.

It comes down to the principle of leverage - the more leverage (lower gear) the easier it is to move object.

[Gerrit Loubser]

The V5M31 5 speed manual gearbox used in the Gen 3 Pajero is a very well designed, durable gearbox. It was clearly designed from scratch as a five speed gearbox (not a 4 speed with an additional gear grafted on). The box is a typical modern countershaft design with a main shaft that runs on the same axis as the input shaft, but is not rigidly conected to it. There is also a countershaft or layshaft that runs below the main shaft.

The main shaft has a set of gears that can spin on it, but are not rigidly connected to it and these are in constant mesh with a set of gears that are rigidly connected to the counter shaft.

Starting from the front of the gearbox (the engine end), these gear sets are the 4th gear set, the 3rd gear set, the 2nd gear set, the 1st gear set, 5th gear set and the reverse gear set (which also includes an idler gear on its own shaft in order to reverse the rotation direction). The gears on the mainshaft can selectively be connected to the main shaft through dog clutches. The dog clutches are equipped with conical synchronisers to assist is synchronising the speed of the main shaft and the relevant gear, thus allowing the dog clutches to engage smoothly (without grating).

As one progresses along the shaft the gears on the main shaft get progressively larger from 4th to 1st and the gears that they mesh with on the lay shaft get progessively smaller. The reverse gear set is typically a set of gears of similar size to the 1st gear set. 5th gear reverses the picture somewat, as it requires a very small gear on the main shaft and a very large on on the layshaft. This arrangement does mean that the diameter of the layshaft has to step down in diameter as one moves towards the back of the gearbox.

Mitsubishi have created a very well balanced design where there is a support bearing for the main shaft at the front, another just after the first gear set and another after the reverse gear set, so that all gear sets can enjoy bearing support on both sides (no gear set runs on a cantilevered shaft as in some other designs). The spacing of the support bearings is also appropriate for the thickness of the main shaft.

This means that the V5M31 gearbox is unlikely to exhibit less durability in 5th gear than in 1st, 2nd or 3rd, but 4th gear is special in terms of durability. This is because 4th gear is a direct drive gear and a direct drive gear is very special indeed as far as gearbox durability is concerned. In fact, there is no other gear selection that can even be compared.

You see, selecting a direct drive "gear" actually isn't selecting a gear at all. Effectively the gearbox is being removed from the torque transmission chain completely:
When a direct gear is selected, the countershaft (or layshaft) and all the gearsets spin along without transmitting any drive torque, while the input shaft is coupled directly to the output shaft. The fact that the gearsets are not transmitting torque obviously means that they are not subject to the stress of transmitting torque and hence are not picking up much wear or fatigue damage. It also means the following:

1) No axial thrust loads are generated by the helical gears. Hence essentially no wear occurs on thrust bearings.
2) No radial thrust loads are generated (due to the gear tooth pressure angle, gears in mesh try to force themselves away from one another). This means that the mainshaft and countershaft bearings are essentially not loaded much either, so minimal wear occurs here.

The result is inescapable: If it is possible to stay in a direct drive gear for most of the time, gearbox wear should be minimized in terms of the actual gearbox internals. This remains so, regardless of how beefy the designers made all the gears and bearings.

One other point to consider is torsional vibration. The primary source of torsional vibration in the driveline is the pulsating torque outpout from the motor, with a torque spike every time a cylinder fires. A four cylinder motor has fewer firing pulses per revolution than a six, eight, ten, twelve or sixteen cylinder running at the same speed and power and this leads to greater torque pulsing in the driveline of the four pot. Fatigue is a mechanism that depends on varying stress ranges and the more the torque variation per revolution is, the greater the stress range variation will also be.

This is not the whole story, though. Because we are dealing with a dynamic system with multiple degrees of freedom, there are several resonant frequencies. If the torque pulses occur at or in the vicinity of a resonant frequency the driveline torque can be multiplied to several times the original value. Drivetrain resonant frequencies depend on the magnitude and distribution of the various rotating masses, the torsional stiffness of the shafts, the presence of any dampers or torsional springs, etc. in the drivetrain. In general, one finds, though, that the amount of energy associated with resonance diminishes as the resonant frequency increases. In other words, it is generally less damaging in terms of torsional vibrations, to run the motor at a higher speed for a given load or power setting.

I don't really tow with the Pajero, but for the reasons mentioned above, I use fourth gear wherever possible when towing the Xplorer on the open road with the Patrol. I simply adjust my speed to around 100 km/h and enjoy the trip, knowing that I am being as kind as possible to the driveline (the Patrol also has quite a decent five speed box) and that I am towing at a comfortable and safe speed.

[4ePikanini]

Fantastic post again Gerrit!

[Gerrit Loubser]

Thanks Marius. I am sitting here at...

bellogo_small.jpg (32.01 KiB) Viewed 2870 times

...checking bills of material for a proto machine we are building later this year. Frankly it is rather boring stuff, so I rather killed some time typing a reply...