My crazy diff ratio change idea

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RRMaximus said:
I looked at your PDFs.

While the gearbox has those two sensors it also has information about which gear it is in, the road speed of the car (from the ABS), the throttle position and the RPM of the engine.

I'm not surprised that the eight speed does not lock up easily given that it was probably intended to be used by people driving in Germany on the autobahn at higher speed.

The gearboxes are from ZF which is a German company so they would be made for the German roads.

Also Range Rover's are sold worldwide and there are many countries where the speed limit is higher than England.

I'm not overly concerned about the torque converter not locking up because I can get the answer using my OBD reader very quickly.

If someone has actual knowledge of ZF gearboxes and can tell me that my change will definitely stop the torque converter locking up than that is a different thing.

I'm not going to spend hours reading through technical manuals that don't answer the question when my OBD reader will do that.
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The auto box is controlled electronically and the firmware can be adapted for many different situations just as it will be different for the petrol engine compared to the diesel.
 
If your diffs new diffs fit physically.
Your torque converter will spend more time out off lockup. That will result in more heat in your atf fluid so a slight decrease in atf fluid lifetime.

Then higher cylinder pressures. It will take x amount of energy to move the car down the road at a certain speed. In order for your engine to produce x amount of energy but at lower rpm it will have to output more torque. Torque is directly related to cylinder pressure. So if your rpm drops by 20% your torque will go up by 20% for the same amount of energy output. If your torque is up by 20% that means cylinder pressure is up by 20%.
Thats not taking into account that engine efficiency changes with rpm so at low rpm you usually have bad efficiency then where the engine makes peak torque you have peak efficiency and then efficiency gets worse again as rpm increase.
So if you drop your engine rpm too far below your peak torque rpm your cylinder pressure will have to be even higher than 20%.
 
If you just going to scarp it why all the bother? Just thrash it down the road at 1500rpm instead of 1200rpm and be done with it.
 
RRMaximus said:
I think you are imagining an extreme situation and not looking at this in reality.

For example, someone else said that the oil pressure would be lower and that would damage the engine.

But I can drive now at 40mph at the same approximate revs as I will have at 50mph with the changed diffs and my engine has plenty of oil pressure at those RPM.

It might be 5% less oil pressure than normal which will be way inside what is required.

I think that you people are imagining things at an extreme to make an irrelevant point.

How much higher cylinder pressure would there be?

Do you have a way to calculate that?

How much extra wear would there be?

Lugging might happen if I was driving at 20mph in 5th gear, with the throttle wide open, but that will not be happening.

Given the low down torque of my engine, and the VANOS system, driving at 1,500 versus 1,900 at 70mph will not cause lugging.

The 6 speed L322 will do about 1,900 RPM at 70mph and the 8 speed L322 will do about 1,400 RPM at 70mph.

Why would Range Rover lower that RPM if there are so many issues with doing that?

Your comment only makes sense if I was loading up my car with a heavy trailer, but I am running it very light, as mentioned already.

Therefore the engine will be operating at the least weight end of the scale that it has been designed to run at, and it will easily handle the load of that weight at a lower RPM.

All of this has been explained by me already.

If I was driving a high revving 4 cylinder engine with a huge load at a low RPM in a high gear with the throttle fully open then I could accept your comment.

That is not the case at all, as my engine has a lot of low down torque.

This is just like someone who changes up gears early in a manual car because they do not need to squeeze that last bit of acceleration out of the car.

In normal operations this puts less stress on the engine.

Likewise, holding a car in lower gears longer than needed puts more stress on an engine.

In an extreme example there could be issues, but they typically come when the throttle is wide open, which is nowhere near where I will be in my modified L322.

As someone said on another forum, they knew someone who did something similar and they had no issues, just a reduction in their acceleration, which I do not care about.
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I mentioned oil pressure and water pump for cooling. I don't know if it will be an issue but it is something I would keep an eye on in case it becomes an issue. I'm not a motor engineer, I am a tinkerer and I am well aware that these things are fiendishly complex with lots of trade-offs. I'm sure there will be other trade offs. Will they be ok, livable with or catastrophic? Don't know. You've checked what you can and it looks OK so time to try it but with an eye scanning for Captain Cockup trying to muscle in.

Like I say, I will be interested to see how it turns out. Best of luck.
 
RRMaximus said:
I looked at your PDFs.

While the gearbox has those two sensors it also has information about which gear it is in, the road speed of the car (from the ABS), the throttle position and the RPM of the engine.

I'm not surprised that the eight speed does not lock up easily given that it was probably intended to be used by people driving in Germany on the autobahn at higher speed.

The gearboxes are from ZF which is a German company so they would be made for the German roads.

Also Range Rover's are sold worldwide and there are many countries where the speed limit is higher than England.

I'm not overly concerned about the torque converter not locking up because I can get the answer using my OBD reader very quickly.

If someone has actual knowledge of ZF gearboxes and can tell me that my change will definitely stop the torque converter locking up than that is a different thing.

I'm not going to spend hours reading through technical manuals that don't answer the question when my OBD reader will do that.
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Phil is the guru on these boxes. Whatever he says.
 
Speaking from very recent experience, if an suto box runs for any petiod of time with less than the normal amount of fluid in it, it will soon be curtains for the box. And mine had less of a hard time than the OP's one did.
 
marjon said:
So if your gona drive it there and scrap it why bother with any of this bollocks :vb-confused2:

J
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I'm not driving it there to scrap it on this trip, instead I need it to make it all the way there and back without any problems. I have stated repeatedly that this will be a return trip.

It may be another few years before I leave England and at that future time I will scrap it. Unless somebody wants to come and get it.

Are you asking me these questions just to attack me or do you have an actual reason for wanting to know this information? I came here to ask a question about my car and it seems like I have to answer personal questions about my life every few comments.
 
Datatek said:
The L322 torque convertor has a multi stage lock up, it's not ON/OFF. It's not directly wheel speed related but load (torque) related. Light load and throttle will se my P38 lock the torque convertor at 50mph, heavy load like caravan on the hook or going uphill it will stay unlocked at 50mph. Taller gearing is like having a trailer on or going uphill and as the L322 uses multi stage torque convertor lock up, I can see it spending more time slipping the lock up clutch than is good for it.
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And for the 3rd time I will find this out with my OBD reader so I'm not worried.
 
pwood999 said:
If you're offended by words like "kiddo", or the other sentences in Mark's initial post, then you definitely need to man up.

There was definitely absolutely nothing in there that was offensive, racist, abusive or otherwise !!

It's called banter, and common place on this forum - get used to it or go elsewhere dude.
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I was not offended by it. But have a look at the second comment. Then the third comment, the fourth comment, the fifth comment, the six comment etc.

But if you want to call it banter then everything that I have said back to you guys is just banter.

When I call you guys idiots for saying really dumb things or for trying to play a game of gotcha questions it's just banter.

Why are you getting offended by my banter?
 
Stanleysteamer said:
Speaking from very recent experience, if an suto box runs for any petiod of time with less than the normal amount of fluid in it, it will soon be curtains for the box. And mine had less of a hard time than the OP's one did.
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My gearbox did not have a hard time, it had about three days of missing gear changes on a 10 minute drive, and then I stopped driving it, found the leak, fixed it and filled it up again.
 
f2c28d76d0bd0c1d606f663e517e4ca1.gif
 
FEI said:
If you just going to scarp it why all the bother? Just thrash it down the road at 1500rpm instead of 1200rpm and be done with it.
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I'm not going to scrap it immediately. Maybe in a few years time when I leave England. On my one month trip to Portugal and back I needed to not break down and therefore I would prefer to run it at a lower RPM.
 
Grrrrrr said:
I mentioned oil pressure and water pump for cooling. I don't know if it will be an issue but it is something I would keep an eye on in case it becomes an issue. I'm not a motor engineer, I am a tinkerer and I am well aware that these things are fiendishly complex with lots of trade-offs. I'm sure there will be other trade offs. Will they be ok, livable with or catastrophic? Don't know. You've checked what you can and it looks OK so time to try it but with an eye scanning for Captain Cockup trying to muscle in.

Like I say, I will be interested to see how it turns out. Best of luck.
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Thanks. People drive at 1,300 RPM at lower speeds for long periods and have no concern for the water or oil pressure. If it was running at 500 RPM I would consider that fact, but it will be running in a typical rev range.
 
Should be fun when your (generic?) OBD reader tells you on the autoroute that the torque convertor is not locking up and you are not in top gear. I doubt that you can manually force the selection of top gear, the electronics decide when to shift not you.. My old diesel runs happily at over 2k rpm on the autoroute. As said repeatedly, lower revs/taller gearing requires more torque which equals more strain on the engine not less.
 
FEI said:
If your diffs new diffs fit physically.
Your torque converter will spend more time out off lockup. That will result in more heat in your atf fluid so a slight decrease in atf fluid lifetime.

Then higher cylinder pressures. It will take x amount of energy to move the car down the road at a certain speed. In order for your engine to produce x amount of energy but at lower rpm it will have to output more torque. Torque is directly related to cylinder pressure. So if your rpm drops by 20% your torque will go up by 20% for the same amount of energy output. If your torque is up by 20% that means cylinder pressure is up by 20%.
Thats not taking into account that engine efficiency changes with rpm so at low rpm you usually have bad efficiency then where the engine makes peak torque you have peak efficiency and then efficiency gets worse again as rpm increase.
So if you drop your engine rpm too far below your peak torque rpm your cylinder pressure will have to be even higher than 20%.
Click to expand...

You said: "If your diffs new diffs fit physically."

I have enough reason to believe they will fit based on the information that I have received here and another places.

You said: "Your torque converter will spend more time out off lockup."

The jury is still out on that. It depends on what input factors are used by the gearbox to make the decision to engage or disengage the lock up clutch. So far no one has been able to find the answer to this question.

I will be able to check this with my OBD reader so I can see if this is a problem or not before I leave on the trip. If it is a problem I will go back to the original differentials.

You said: "Then higher cylinder pressures. It will take x amount of energy to move the car down the road at a certain speed."

I am sorry but I do not agree. Running in a higher effective gear ratio will create a fuel saving on the trip. Like any time you drive in a high gear. Try driving on the highway in third gear for a month and then you will see your fuel consumption go up.

That is part of the reason why Range Rover moved to a six speed gearbox and eventually an eight speed gearbox for these cars, and moved away from the four speed in the P38.

If I am burning less fuel then I am creating less energy then I cannot be creating more pressure inside the cylinder. Where does this pressure come from if not from the energy of the fuel? By burning less fuel I am spending less energy and creating less pressure.

Maybe this change will not cause a saving in fuel, if the engine was lugging at low RPM, but I will not be not running in a low RPM. I think people somehow calculated that I will be running at 500 RPM or something like that, but it will be running well over 1,000 RPM for most of the trip. I have not calculated the exact RPM and I really don't care to do that but you are welcome to make the calculation.

You said: "Thats not taking into account that engine efficiency changes with rpm so at low rpm you usually have bad efficiency then where the engine makes peak torque you have peak efficiency and then efficiency gets worse again as rpm increase."

With the VANOS system this engine has a relatively straight torque curve from 1,000 RPM to 3,500 RPM. I will be dealing in the 1,000 RPM to 2,000 RPM range so it won't matter in terms of efficiency where in that rev range I am driving.

You said: "So if you drop your engine rpm too far below your peak torque rpm your cylinder pressure will have to be even higher than 20%."

At 70 mph I will be driving at an engine RPM that would normally be experienced when driving at 50 mph so well within the normal operating parameters of the engine.

The only time the RPM would be low is driving away from rest. Given that 90% of this trip will be driving on highways across Europe this will be a very small part of the trip.

As my car will be low in weight this will still be in the operating parameters of the car, given that the car is designed to be able to tow more than 100% of its weight.

If I was doing this and towing a caravan and four people in the car then that would be a completely different situation.

This is more like somebody putting larger off-road tires on the car, and I have seen no conversations about how that would cause a multitude of problems with this engine.

The torque and power curves of this engine are in the image below and I can see no significant issue based on this chart.
 

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Datatek said:
Should be fun when your (generic?) OBD reader tells you on the autoroute that the torque convertor is not locking up and you are not in top gear. I doubt that you can manually force the selection of top gear, the electronics decide when to shift not you.. My old diesel runs happily at over 2k rpm on the autoroute. As said repeatedly, lower revs/taller gearing requires more torque which equals more strain on the engine not less.
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I am not really sure why you keep attacking my OBD reader when it is one of the better known brands and there are many videos on YouTube with Range Rover enthusiasts in the UK using this brand with great effect.

Yes it is not the top of the range gap tool but it is perfectly good and has a wide range of functions and analysis options.

The ODB reader that I have is specifically for Jaguar Land Rover vehicles and not generic.

I will not start on my journey and then check the torque converter lock up issue because that would be the dumbest thing that I could possibly do.

I have repeatedly said that I will check the lockup before I leave and if it is a problem I will revert back to the original differentials.

This is why I find this particular forum such a joke, because you ignore everything that I say, create a situation that will not exist, and then attack me for that situation.

My car is not your car and your car might be happy driving for 6,000 miles at 2,000 RPM but my car is different.

The difference in torque will be 300Nm to 350Nm based on the torque curve, yet the travel of the cylinders inside the bores will be 24% more based on the increased RPM.

Also given that there will be a fuel saving, I will be spending less energy in terms of used fuel so I cannot see where this extra pressure on the cylinder comes from, burning less fuel.

If there is a way to create more pressure while using less fuel then patent it because you will become a billionaire from this process.

There is a reason why modern cars have more gears, and one of those reasons is to run at a lower RPM while at higher speed.

I will not be running at an extremely low RPM, in fact it will be a normal RPM for people who are driving around in rural England at 50 mph.

As for going into fifth gear, the gearbox is manually selectable and I already know that I can select fifth gear when it chooses to run in fourth gear, because I have done this in my normal driving.

While the computer will decide what gear it goes in when I am driving in automatic, this gearbox has manual selection as well and I have already explained this fact before.

Given that it automatically selects fifth gear well below the 70 mph or 80 mph that I will be driving at, I cannot see this being a problem.

If I was driving consistently at 50 mph with this altered differential then there may be a problem but that is not what I will be doing.

Please stop making up problems that do not exist or that I can determine before I leave, and then solve easily by reverting back to the original differentials.

If you have actual knowledge of actual problems that will actually occur then please share them with me.
 
RRMaximus said:
I am not really sure why you keep attacking my OBD reader when it is one of the better known brands and there are many videos on YouTube with Range Rover enthusiasts in the UK using this brand with great effect.

Yes it is not the top of the range gap tool but it is perfectly good and has a wide range of functions and analysis options.

The ODB reader that I have is specifically for Jaguar Land Rover vehicles and not generic.

I will not start on my journey and then check the torque converter lock up issue because that would be the dumbest thing that I could possibly do.

I have repeatedly said that I will check the lockup before I leave and if it is a problem I will revert back to the original differentials.

This is why I find this particular forum such a joke, because you ignore everything that I say, create a situation that will not exist, and then attack me for that situation.

My car is not your car and your car might be happy driving for 6,000 miles at 2,000 RPM but my car is different.

The difference in torque will be 300Nm to 350Nm based on the torque curve, yet the travel of the cylinders inside the bores will be 24% more based on the increased RPM.

Also given that there will be a fuel saving, I will be spending less energy in terms of used fuel so I cannot see where this extra pressure on the cylinder comes from, burning less fuel.

If there is a way to create more pressure while using less fuel then patent it because you will become a billionaire from this process.

There is a reason why modern cars have more gears, and one of those reasons is to run at a lower RPM while at higher speed.

I will not be running at an extremely low RPM, in fact it will be a normal RPM for people who are driving around in rural England at 50 mph.

As for going into fifth gear, the gearbox is manually selectable and I already know that I can select fifth gear when it chooses to run in fourth gear, because I have done this in my normal driving.

While the computer will decide what gear it goes in when I am driving in automatic, this gearbox has manual selection as well and I have already explained this fact before.

Given that it automatically selects fifth gear well below the 70 mph or 80 mph that I will be driving at, I cannot see this being a problem.

If I was driving consistently at 50 mph with this altered differential then there may be a problem but that is not what I will be doing.

Please stop making up problems that do not exist or that I can determine before I leave, and then solve easily by reverting back to the original differentials.

If you have actual knowledge of actual problems that will actually occur then please share them with me.
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f2c28d76d0bd0c1d606f663e517e4ca1.gif
 
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