Whoops, bet that'll cost a bit to fix

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Originally Posted by chazza

Isn't it true though, that when in Drive the box can shift up and down excessively say between D and 3, which causes overheating? I always leave the Disco in 3 on hills.

Cheers Chazza

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Well I understand that the box when in parameter "D" can use all forward drive gears and hence overheats by picking up a gear that is too high and straining. VY commodores are notorious for doing this around town in D, so much so we use 3 all the time and D when needed and the fuel consumption is heaps better.

Sticking it in 2 though and the box has only these two ratios to play with and hence wont attempt to pull a gear that is too high.

After my neighbour told me of his woes with the autobox on his 97 tdi going to mt hotham, he uses 3 or 2 for mountainous work and also descending the hill to minimize excessive brake use.

when in D its not the number of gears its the fact that it picks top and then leaves the TC unlocked or unlocks it to keep it on top cog rather than downshift and let the engine rev Which saves you fuel.

The problem with this is its the automatics equivelent of riding the clutch and we all know thats a bad thing.


Excessive use of the TC at speed pushing tall gears will quickly heat the oil and it will break the oil down causing it to loose lubricity, once it starts to loose lubricity the gears get hot, when the gears get hot they heat the oil even more which again helps break down the oil... you get the idea....

as the engine isnt doing lots of rpms and as the oil cooler is typically fed from either the TC overflow or the regulator dump valve from the main pump there isnt a whole lot of flow too the cooler and the cooler is quickly overwhelmed....


Thats how you toast an auto by staying in D, locking 3rd (or 4th) forces it to lock up the TC which drops the thermal loading on the oils and components.