I have been mulling over the question of using TC, or rear diff lock or both together, for some time. As this is a somewhat longwinded discourse, I have hesitated in asking the questions, not wanting to bore many of you. Also, if this is better put in the general areas of the forum rather than the Gen4 specific, please feel free to move.
As most of you will know, when you activate the rear diff lock, it deactivates the ABS, TC and ASC and I have always wondered why this should be so. The ASC can’t work with the diff lock on, so I had wondered if it being off meant the TC had to be, too, but it is already possible to deactivate ASC and keep TC working. So is the reason because:
I can envisage that, on sand, activating the diff lock and thereby deactivating TC would be an advantage, whether in 4HLc or 4LLc. However, I assume usually the rear diff lock is activated when in 4LLc and needing to go uphill. So, what are the circumstances that mean, were it available, TC for the front wheels might be required or desirable with the rear diff lock activated? If both front wheels are not, or either one of the rear wheels is not, slipping (that is, the wheels are rotating faster than the corresponding ground speed) then TC wouldn’t come on because, as the centre diff is locked, if either pair is not slipping the other pair won’t be either (even if one of the front wheels is in the air). So, the only circumstances when the TC for the front wheels might activate is if the rear wheels are slipping and one or more of the front wheels is slipping, at a different rate of slippage (or in the air). Any forward motion is generated by the slipping torque from the rear wheels plus the transferred torque on the other front wheel.
If one is cross axled and rear diff lock is on, then only one rear wheel will be providing forward push. If, as before, there is some slippage in the rear wheel in ground contact, having TC and rear diff activated might be an advantage but is it better than just TC alone, which would still give you 2 wheels pushing?
Are there other circumstances where TC and rear diff lock operation would both be required or desirable? Does this give rise to potential damage or problems?
Surely it isn’t that MMC are just slack. Other car makers do the same (deactivating TC with rear diff lock).
Is any of the above just bovine excrement? Please feel free to argue or provide insight.
Admin: moved to "Where the rubber hits the road", as the forum nominated for discussion of locking diffs - and this discussion is relevant to more than just Gen 4 Pajero.
As most of you will know, when you activate the rear diff lock, it deactivates the ABS, TC and ASC and I have always wondered why this should be so. The ASC can’t work with the diff lock on, so I had wondered if it being off meant the TC had to be, too, but it is already possible to deactivate ASC and keep TC working. So is the reason because:
- it may cause a problem or damage in some circumstances, or
- MMC couldn’t be bothered programming it as such, or
- TC isn’t effective when the rear diff lock is activated?
I can envisage that, on sand, activating the diff lock and thereby deactivating TC would be an advantage, whether in 4HLc or 4LLc. However, I assume usually the rear diff lock is activated when in 4LLc and needing to go uphill. So, what are the circumstances that mean, were it available, TC for the front wheels might be required or desirable with the rear diff lock activated? If both front wheels are not, or either one of the rear wheels is not, slipping (that is, the wheels are rotating faster than the corresponding ground speed) then TC wouldn’t come on because, as the centre diff is locked, if either pair is not slipping the other pair won’t be either (even if one of the front wheels is in the air). So, the only circumstances when the TC for the front wheels might activate is if the rear wheels are slipping and one or more of the front wheels is slipping, at a different rate of slippage (or in the air). Any forward motion is generated by the slipping torque from the rear wheels plus the transferred torque on the other front wheel.
If one is cross axled and rear diff lock is on, then only one rear wheel will be providing forward push. If, as before, there is some slippage in the rear wheel in ground contact, having TC and rear diff activated might be an advantage but is it better than just TC alone, which would still give you 2 wheels pushing?
Are there other circumstances where TC and rear diff lock operation would both be required or desirable? Does this give rise to potential damage or problems?
Surely it isn’t that MMC are just slack. Other car makers do the same (deactivating TC with rear diff lock).
Is any of the above just bovine excrement? Please feel free to argue or provide insight.
Admin: moved to "Where the rubber hits the road", as the forum nominated for discussion of locking diffs - and this discussion is relevant to more than just Gen 4 Pajero.
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