Low-range question

[Galvo]

Ok boys what do you think of this.

Went up to Lake Eucumbene (NSW) over the weekend for a fish and catch-up with the mates. Fishing was slow and I decided to go find some fun. From our camp you could see a reasonably steep grassy hill – mates dare me so off I go, drive up it no probs, car was in Auto mode. Get back to camp and we spot another steeper grassy hill close by – so off I go again. This hill is very steep and I only have the original Kumos on ( done 27,000kms) and don’t bother to pressure down. So up I go and get up with ease, passenger is a Pajero driver and was impressed. I turn around up the top and come down with the hill decent on – very impressed now!!

I turn around down the bottom and put it in “low” raise it up and set off up the hill again, get half way up and wheels start spinning. Reverse back down (with a fair bit of sliding) and try again – no go. Tried about half a dozen times and had to give up!! What happened?? I tried different lines and different speeds but couldn’t get up in low range.

Pajero driver has a crack at it the next morning (no frost) and drives straight up. So I jump back in the GC (now this could be embarrassing), leave it in Auto and drive straight back up the bloody thing.

So my question is why wouldn’t it get up the hill in low range? I would have thought it would make it easier.

[Numb Thumbs]

Too much torque and so breaking traction?

Cheers
Numb Thumbs

[Savvas]

Originally Posted by Galvo

Ok boys what do you think of this.

Went up to Lake Eucumbene (NSW) over the weekend for a fish and catch-up with the mates. Fishing was slow and I decided to go find some fun. From our camp you could see a reasonably steep grassy hill – mates dare me so off I go, drive up it no probs, car was in Auto mode. Get back to camp and we spot another steeper grassy hill close by – so off I go again. This hill is very steep and I only have the original Kumos on ( done 27,000kms) and don’t bother to pressure down. So up I go and get up with ease, passenger is a Pajero driver and was impressed. I turn around up the top and come down with the hill decent on – very impressed now!!

I turn around down the bottom and put it in “low” raise it up and set off up the hill again, get half way up and wheels start spinning. Reverse back down (with a fair bit of sliding) and try again – no go. Tried about half a dozen times and had to give up!! What happened?? I tried different lines and different speeds but couldn’t get up in low range.

Pajero driver has a crack at it the next morning (no frost) and drives straight up. So I jump back in the GC (now this could be embarrassing), leave it in Auto and drive straight back up the bloody thing.

So my question is why wouldn’t it get up the hill in low range? I would have thought it would make it easier.

The torque is being multiplied more so in low range than in high range, so it will break traction sooner. If you had aired down the tyres than you probably would have made it up and it would have been effortless for the car.

Did you happen to notice what sort of revs the engine was doing each time in Auto and then in Low?

[Galvo]

Thanks guys, interesting couple of comments about too much torque. I didn’t give it many herbs on the first couple of attempts (when in low) I tried to go up as slow as possible. I gave it a bit more revs each time before having to give up, plus I didn’t want to cut up the hill too much. I wasn’t taking notice of revs but was very surprised when I couldn’t get up when I was in low range.

I should say I’m not a complete novice at four wheel driving but it certainly brought it home I have a lot to learn. I’ll be replacing the Kumos with Nittto’s or Coopers in the not too distant future because I still have the 20’s on. If I run into more trouble I’ll replace the 20’s with 18’s so I can pressure down properly.

[Fruju]

I might be talking out my Rs, but 4lo is for high traction offroad surfaces like rocks and dirt. With the increased torque that low gives, you are more likely to break traction on a low traction surface like grass.

Also in 4lo the centre diff is locked so the front and rear axles are turning at the same speed so when your wheels start to spin there is very little speed differential so therefore the traction control won't cut in unless it detects the vehicle sliding sideways.

[Nicholas]

Originally Posted by Fruju

I might be talking out my Rs, but 4lo is for high traction offroad surfaces like rocks and dirt. With the increased torque that low gives, you are more likely to break traction on a low traction surface like grass.

Also in 4lo the centre diff is locked so the front and rear axles are turning at the same speed so when your wheels start to spin there is very little speed differential so therefore the traction control won't cut in unless it detects the vehicle sliding sideways.

Ditto to this and what everyone has been saying, 4low in the w2k is really only for rock crawling the system works better in every case in 4hi. The computers seem to be a lot more coherent in 4hi as they have more control over the traction control due to the centre diff not locking

[JamesLaugesen]

I'd say either the grass was slippery from the previous runs (or a more slippery section.), or you were going too slow or too jerky on the throttle without noticing.

The "torque" at the wheels is irrelevant if you're approaching at the same speed (wheel RPM is the same.) with the same 'smoothness' on the throttle.
The actual torque is a function of the tyre grip, diameter and acceleration.
Potential torque is higher in low range, but the actual torque is exactly the same (since you obviously had enough torque to get up in low range too.).

Oh unless the WK2 guys know of anything weird about the traction control in low range which could explain it too?