Thread: Oil Question Again

Originally Posted by BradC

I don't think that's being suggested. My take is they are suggesting the crank in the 3L is weak, and susceptible to lugging. The implication is the TDV6 isn't going to stress the crank as much as the SDV6 so don't remap.


I believe that would be the logical implication.

The lugging argument was a theory being floated on a South African LR forum. The suggestion on the forum was also a remap helps as it means the engine does not have to work as hard.

The reality is unless you have a manual - the only time the motor sees full torque at low revs is with your foot flat to the floor when launching off the lights (a common event when lined up against a 4WD Toyota. ). Even then the stall speed of the torque converter is keeping the revs up.

I have never heard of anyone saying their crank snapped when launching from a standing start. I suspect this comment may have been a comment on how Vera drives her manual D3.

The crankshaft failures are either spun bearing or fatigue related.

Spun bearings are either - an assembly problem due to not enough crush or poorly located bearings due to no assembly lugs, or an oil viscosity problem - either too thick of an oil when cold causing the bearing to grab and spin, or too thin of an oil when hot resulting in metal on metal contact.

This is why oil grade is so important to get right.

And fatigue related failures, which are contributed to by the weak crank design, would be due to an insufficient bearing journal undercut radius, and as such are more likely due to high revs - not low revs. A remap helps you keep the revs down, use less throttle, whilst not needing to lug the motor either. The extra weight hanging off the crank on the Discovery compared to say the Territory motor adds to this fatigue stress.

This is what Ford claim to have addressed with the upgraded crankshaft in the motor that was used in the F-150, and now in the new Ranger.

A more sensible advice would be to avoid spending lots of time at very high speed which equals higher revs. As you would see in Europe or South Africa.

Oh - and Vera - stop lugging your motor!

Originally Posted by DiscoDB

And fatigue related failures, which are contributed to by the weak crank design, would be due to an insufficient bearing journal undercut radius, and as such are more likely due to high revs - not low revs. A remap helps you keep the revs down, use less throttle, whilst not needing to lug the motor either. The extra weight hanging off the crank on the Discovery compared to say the Territory motor adds to this fatigue stress.

More torque at lower rotational speed means more load/stress on the crankshaft. For the same amount of power at a lower speed you need a bigger bang (higher combustion chamber pressure). I'm no mechanical engineer, but surely that's more fatiguing than spinning faster.

It can but it is hard to put many cycles at full torque on the crank at this low rpm scenario with an auto under normal use. You would have to lock it in a gear and then intentionally hold it at a constant speed under full load for an extended period of time.

So yes if you tried hard enough you could do this - but do we really think the people who snapped a crank are putting their cars under this type of forced punishment?

Now with a manual very easy to lug the motor for extended periods of time as Christian describes - like on a long steep hill - which you will find lots of near Christian and Vera’s house. Vera - do take note!

The unknown here is understanding what the natural resonant frequency of the crankshaft is and how well is the LR use of this motor set up for torsional vibration compared to say the same motor in a different application with different masses attached to or driven by the engine.

Originally Posted by DiscoDB

It can but it is hard to put many cycles at full torque on the crank at this low rpm scenario with an auto under normal use. You would have to lock it in a gear and then intentionally hold it at a constant speed under full load.

So yes if you tried hard enough you could do this - but do we really think the people who snapped a crank are putting their cars under this type of forced punishment?

Now with a manual very easy to lug the motor for extended periods of time as Christian describes - like on a long steep hill.

The unknown here is understanding what the natural resonant frequency of the crankshaft is.

I am normally a pretty sedate driver, and have to admit that, despite Cambo's engine and transmission remap magic, my wee beastie still likes to idle along at about 1100 rpm in 8th, and it can take a reasonable amount of right foot movement before it will drop down a gear for even relatively gentle accelerating (without towing the brick of course).

To my sensitive rear end the car is at the very least on the verge of labouring in this scenario.

I wonder if this is mapped as a supposedly more economical situation, although I agree with the comments here that higher revs in a lower gear is a preferable result.

Well if you can hold high load at 1100rpm - then yes this would not be good.

I would definitely avoid that scenario.

With the unmapped 2.7 I am sure mine just drops back to 5th and wouldn’t stay in 6th at such low rpm unless I have next no throttle.

Maybe that is a problem with the 3.0 - the gearing and transmission mapping is wrong that it does let you hold low rpm at high load for extended times without realising it.

Could turn out to be not such a dumbass observation after all. 🤣

Originally Posted by DiscoDB

Well if you can hold high load at 1100rpm - then yes this would not be good.

I would definitely avoid that scenario.

With the unmapped 2.7 I am sure mine just drops back to 5th and wouldn’t stay in 6th at such low rpm unless I have next no throttle.

Maybe that is a problem with the 3.0 - the gearing and transmission mapping is wrong that it does let you hold low rpm for extended times without realising it.

Could turn out to be not such a dumbass observation after all. 🤣

Mine does it as well with Cambo's tune and at 1100/1200 rpm at 80 kph on the flat it is not under any load whatsoever and is simply idling along doing it very easily. Mind you, prior Cambo's tune it did the same thing; it's a gearing/torque thing with the 3.0 litre....

I really think that many of the comments are overthinking the situation. From what I read re engine probs, there was a batch of faulty crankshafts which were not heat treated correctly and which caused snapping/breaking or whatever you wish to call it.

Can anyone confirm if later engines say, past MY11-12 ish, (my guessing-- I may be a year out) have suffered from snapped shafts?

The second problem was the bearing shells rotating and cutting off oil supply due to incorrect assembly a la Service Bulletin.

Having said that, I think we all agree that oil grade/quality/change intervals etc also has a significant affect on bearing life.

Just my 2 bobs worth anyway.

Originally Posted by Discodicky

Mine does it as well with Cambo's tune and at 1100/1200 rpm at 80 kph on the flat it is not under any load whatsoever and is simply idling along doing it very easily. Mind you, prior Cambo's tune it did the same thing; it's a gearing/torque thing with the 3.0 litre....

Would only be bad if there is a bad natural harmonic happening at this low speed as well.

You would probably be using less than 20-30% of the available torque to hold speed on a flat at such low RPM, and less than 10% of the peak torque available at 2000rpm.

Originally Posted by Discodicky

Can anyone confirm if later engines say, past MY11-12 ish, (my guessing-- I may be a year out) have suffered from snapped shafts?

I’ve read of these snapping even in the early D5s