My crazy diff ratio change idea

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300bhp/ton said:
Have you got any mechanical knowledge at all? An MoT tester saying a diff is rusty just sounds like a poor dodgy MoT tester tbh.

The ratio change you are proposing is HUGE, have you bothered to use a gearing calculator to see what the actual impact would be?

Why on Earth do you think running at higher revs in its current state would be bad anyway? It already has pretty long tall gearing, just go and look at how most high revving 4 cylinder cars are geared.

Are you 100% sure the diffs didn't change in any other way during production? Are they 100% a direct swap over? Not saying they aren't, I don't know. But the L322 was built for many years and changed a lot in that time.
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My diffs are incredibly rusty. I mentioned that they are so rusty that the MOT guy mentioned them but I already was aware that they are really rusty. I am talking about flakes of metal falling off them when you touch them slightly, so badly that you cannot be underneath them as your eyes fill up with metal. Large chunks and small chunks. Really really rusty. I do not need an MOT guy to tell me that, I can see it with my own eyes.

Please do not compare four-cylinder engines to a 23 year-old V8 engine that was actually designed years earlier before it came to the Range Rover. It is about the RPM that the engine runs at compared to its top RPM.

I had a motorbike that would rev to 11,000 RPM but who cares? I am talking about a 2002 petrol 4.4 L V8 Range Rover. And yes I have years of experience working on cars which is why I am talking about changing over the diffs on a forum, to reduce the RPM.

I am not sure if the diffs did not change over time, which is part of the reason that I am posting this comment here. They seem to be the same based on every visual information that I have from looking at the two different diffs on the Gentlemen of Salvage website.

I was hoping that someone with more knowledge than me would be able to answer that question as opposed to someone without knowledge throwing out opinions.

As for the gear ratios, since nothing else would change in the drive train it is a simple ratio of 3.73 / 2.76. That is a 74% difference so if it was reving at 1,500 it would now rev at 1,500 x 74% =1,110. It's not complicated.

(I see that I typed 1,300 rpm before when I should have typed 1,500 rpm, sorry.)
 
RRMaximus said:
I am sorry that I mentioned the fuel aspect, only to stop people saying that it was a waste of money. My main reason is to run the engine at a lower RPM on a long trip. Just to put a little bit less stress on a 23-year-old engine.
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Pulling a higher gear may actually impose more stress on the engine. a wider throttle opening needed to maintain speed, thus higher compression pressures. A lighter load and higher revs does no harm. The 2.76 diffs you say went with the 8 speed auto, so it's likely that under some circumstances, top gear would not be in use.
 
Datatek said:
Pulling a higher gear may actually impose more stress on the engine. a wider throttle opening needed to maintain speed, thus higher compression pressures. A lighter load and higher revs does no harm. The 2.76 diffs you say went with the 8 speed auto, so it's likely that under some circumstances, top gear would not be in use.
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I can manually select 5th gear if needed if it does not automatically change up.
 
Mark Piercy said:
If your concerned about the diff outer casings, as long as there is no oil seepage they're good to go.
Have seen the cars and the rust in the UK that drive in Salt treated roads😵
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I was not concerned but if I changed them for newer diffs without rust that adds a small extra benefit to making the change. I have no plans to change the diffs due to the rust.

My aim was to reduce RPM during steady driving on motorways / highways on a long trip. The fuel saving and rusty diff change are only minor bonuses not my prime motivation.

I only mentioned these factors in passing and I did not expect them to become the focus of so many comments. The main issue is if the different diffs will fit and I have not had any information about that primary concern.
 
RRMaximus said:
Very good point. I do not know how to do emoji but if I did I would do the same face. I am now wondering how to find the torque curve of the 4.4 petrol L322 engine...
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Usually later in the revs range. Most petrol on turbos are at there best around 3k through to 5k revs.
Motor depending also and if there are camshaft timing devices that shift torque points😵🫣
How bloody complicated does it need to be😂
 
Mark Piercy said:
As long as the engine is in it's natural torque curve or it'll labor from the lower revs possibly 🤔
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I think this image is it, for the BMW equivalent M62, showing a straight line due to vanos?

I normally do not get over 1,500 RPM in my daily driving, so I am barely using the power of the car, but I feel no need to do that.

Given that the pulling power below 1,500 RPM is fine for me pulling away from the lights and accelerating into freeway traffic it should be OK for maintaining speed when cruising on a highway in Spain.
 

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RRMaximus said:
I think this image is it, for the BMW equivalent M62, showing a straight line due to vanos?

I normally do not get over 1,500 RPM in my daily driving, so I am barely using the power of the car, but I feel no need to do that.

Given that the pulling power below 1,500 RPM is fine for me pulling away from the lights and accelerating into freeway traffic it should be OK for maintaining speed when cruising on a highway in Spain.
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You may be the first to find out kiddo. 🫵😎
 
RRMaximus said:
The whole point of coming here was to not find out through spending time and money on something that might be pointless.
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Understood, most on here are happy to maintain what they have.
Although there are a few that dabble in mods to suit there needs.
You may be the first to change out diffs in an l322. Most of the time it's the series vehicles that change them. 😊
 
RRMaximus said:
The whole point of coming here was to not find out through spending time and money on something that might be pointless.
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You're always gonna get comment (some good, some bad & some scarcastic) on this forum, but often good info based on extensive knowledge & experience.

If we assume the engine uses more fuel when it working harder (regardless of revs) & producing torque, it would be interesting to see the fuel used of a given distance UK motorway trip at 70mph. Then do the diff swap, & report back from Portugal on the same info.

That way we would all learn if it works or not.
 
BTW, just for a laugh, I googled the amount of energy required. Surely burning that amy energy in petrol is gonna put the same strain or wear on the engine regardless of rpm. . . . . .but I'm not the right scientist :cool:

1751911826682.png
 
pwood999 said:
BTW, just for a laugh, I googled the amount of energy required. Surely burning that amy energy in petrol is gonna put the same strain or wear on the engine regardless of rpm. . . . . .but I'm not the right scientist :cool:

View attachment 344804
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If I am driving at 70 mph in fifth gear and then I forced my gearbox to go into third gear, I will theoretically use the same fuel but I am putting more stress on the components by running them at a faster speed.

I wish to God I never mentioned anything about fuel saving in my initial comment because it was just not my focus.

I only said it because I have read many forums where people say that it's a waste of money to change anything.

On a different form one person just said that I should rent a fuel efficient car if I want to save petrol money.

I don't want to save money, I want to drive my Range Rover to Portugal and back and spend a month there, but I do not want to sit on higher RPMs than necessary on a long trip.

My focus is the RPM not the fuel saving.
 
RRMaximus said:
If I am driving at 70 mph in fifth gear and then I forced my gearbox to go into third gear, I will theoretically use the same fuel but I am putting more stress on the components by running them at a faster speed.

I wish to God I never mentioned anything about fuel saving in my initial comment because it was just not my focus.

I only said it because I have read many forums where people say that it's a waste of money to change anything.

On a different form one person just said that I should rent a fuel efficient car if I want to save petrol money.

I don't want to save money, I want to drive my Range Rover to Portugal and back and spend a month there, but I do not want to sit on higher RPMs than necessary on a long trip.

My focus is the RPM not the fuel saving.
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Less stress a lower torque required.
 
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