Disco 1 - 300TDI Auto (gearbox question)

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D

davethebb

Member
Posts
10
Hi Everyone,
Last year my 2004 D2 died (a tree fell on it) and I am looking at a D1 300TDI auto. I am interested to know if the D1 Auto locks the gear when in Lo Ratio when descending hills etc. Regards, Dave.
 
No. It has know way to know if you are in low, high or neutral

Descending hills ? I have a 300tdi auto in my rangerover...in my profile pic...I drive it in D all the time, up hill or downhill....it has brakes :)
 
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If you select 1,2 or 3 rather than drive, then the gearbox will not change up any further than the selected gear. For example if you select 1 you will only have 1st gear, if you select 2 you will have 1st and 2nd and selecting 3 will give you 1st, 2nd and 3rd, Hi and Lo changes the ratios to the wheels but makes no difference to the way the actual gearbox operates.
 
DiscoRay said:
If you select 1,2 or 3 rather than drive, then the gearbox will not change up any further than the selected gear. For example if you select 1 you will only have 1st gear, if you select 2 you will have 1st and 2nd and selecting 3 will give you 1st, 2nd and 3rd, Hi and Lo changes the ratios to the wheels but makes no difference to the way the actual gearbox operates.
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Thanks DiscoRay. I'm just concerned about the amount of engine braking etc you have with the auto so do you have any experience on this subject?
 
davethebb said:
Thanks DiscoRay. I'm just concerned about the amount of engine braking etc you have with the auto so do you have any experience on this subject?
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In any autobox you will get an amount of engine braking depending on your speed and the gear you are in, but you have to select it manually. So if you go from D to 3 you'll get a bit, then to 2 you'll get more and 1 will nearly stand you on your nose!
I have experience of autos dating back to the 1970s. I now have a Disco 2 auto and even though it is now an electrically signalled box rather than an old fashioned slush box, it is exactly the same from the EB point of view.
Without it, if your brakes failed, at a decent speed, the handbrake might well not cope as it is a transmission brake and could indeed feck the rubber coupling, so you'd need to be able to "change down" through the box to be able to then use the HB to stop the car. So it is a safety feature as well of one that gives you a bit more control and the brakes more of a chance on very steep down gradients.
 
davethebb said:
Thanks DiscoRay. I'm just concerned about the amount of engine braking etc you have with the auto so do you have any experience on this subject?
Click to expand...
I've never done any serious off roading with mine, 99% on road and occasionally poor mountain roads in Greece but I do often use engine braking and have always found it to be adequate although not as direct in feel as a manual.
 
Ive done series offloading....that's what it was built for....as I said above I drive it in D. If it goes to fast I brake, it just does the same thing. The forces are transmitted to the ground through the tyres....you have grip or you dont. Never had a problem, I think engine braking offroad is overratted.....your stuck in your selected gear at a speed dictated by engine revs when using engine braking what do you do if it starts to slide? Me in D I just let the brakes off :)
 
Official advice is to use low gear, as engine braking is much less likely to cause wheel lock-up under braking, which is why HDC in the more modern land rovers uses just that.
It is what off-road driving instructors tell you to do too. So low range, 2nd or first then just let the car down gently.
And here is Land Rover themselves saying exactly this.
https://www.landrover.com.my/owners...ach the hill straight on,4x4 on a steep slope.
 
EeEk said:
Ive done series offloading....that's what it was built for....as I said above I drive it in D. If it goes to fast I brake, it just does the same thing. The forces are transmitted to the ground through the tyres....you have grip or you dont. Never had a problem, I think engine braking offroad is overratted.....your stuck in your selected gear at a speed dictated by engine revs when using engine braking what do you do if it starts to slide? Me in D I just let the brakes off :)
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Foot braking rather than engine braking is far more prone to locking wheels up. Which ultimately gives you less control on certain types of terrain and conditions.
 
Stanleysteamer said:
In any autobox you will get an amount of engine braking depending on your speed and the gear you are in, but you have to select it manually. So if you go from D to 3 you'll get a bit, then to 2 you'll get more and 1 will nearly stand you on your nose!
I have experience of autos dating back to the 1970s. I now have a Disco 2 auto and even though it is now an electrically signalled box rather than an old fashioned slush box, it is exactly the same from the EB point of view.
Click to expand...
Not actively wanting to disagree, but this isn't exactly the case.

With a traditional automatic, you have a a torque converter (aka stall). Which is essentially a viscous coupling. This allows the engine and gearbox to spin at different speeds. Unlike a manual.

So with an automatic off road, you get a lot less engine braking than a manual gearbox, due to the "slip" from the torque converter.

Modern automatics have the ability to 'lock up' the torque converter, usually by means of a clutch plate. This is mostly done for cruising as in top gear when locked up it will prevent the slip from the torque converter and lower rpms and promote better mpg. When locked up, it is essentially acting like a manual gearbox in terms of engine shaft rpm and gearbox rpm.

With vehicles like a Discovery 2 or p38 the gearbox has the ability to lock the torque converter up when in low range too. The D2 does this automatically when you select low range, while there is a switch in a p38 (the sport mode button) that allows this when in low. Locking the torque converter up will give you much better engine braking than an older automatic.
 
300bhp/ton said:
Not actively wanting to disagree, but this isn't exactly the case.

With a traditional automatic, you have a a torque converter (aka stall). Which is essentially a viscous coupling. This allows the engine and gearbox to spin at different speeds. Unlike a manual.

So with an automatic off road, you get a lot less engine braking than a manual gearbox, due to the "slip" from the torque converter.

Modern automatics have the ability to 'lock up' the torque converter, usually by means of a clutch plate. This is mostly done for cruising as in top gear when locked up it will prevent the slip from the torque converter and lower rpms and promote better mpg. When locked up, it is essentially acting like a manual gearbox in terms of engine shaft rpm and gearbox rpm.

With vehicles like a Discovery 2 or p38 the gearbox has the ability to lock the torque converter up when in low range too. The D2 does this automatically when you select low range, while there is a switch in a p38 (the sport mode button) that allows this when in low. Locking the torque converter up will give you much better engine braking than an older automatic.
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Quite right.
"Exactly" was not right for a D1. My bad.
I have a D2 now as my daily drive and forgot about the D1 box, mind you both my D1s are manual anyway!
On the D2, the M button is what locks the box into the gear you have selected in low range.
It will stay in the locked gear, UNLESS you push on the accelerator.
This thread explains it quite well.https://www.4x4community.co.za/forum/showthread.php/45295-Disco-2-Auto-in-Manual-Mode
 
HDC can brake as a minimum an axle or more likely individual wheels. It can also detect wheel slip as soon as it happens. With a foot brake you simply cannot modulate it the same and have no control over individual wheels.
 
EeEk said:
I assume under should be than.
I guess you've never seen a wheel spin backwards under downhill engine braking and the vehicle take off.


HDC uses the brakes.
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Sorry for being so boringly conventional about all this.
And for the record a/ HDC can brake each wheel individually, no driver can do that.
and b/ you can only get HDC working once you have put the tranny box into "low".
But you carry on driving your truck the way you feel is best for you.:rolleyes:
 
EeEk said:
I guess you've never seen a wheel spin backwards under downhill engine braking and the vehicle take off.
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BTW - a wheel rotating backwards when going downhill is a function of having an open diff and lifting a wheel. With open diffs it is always a risk, but more flexy suspension can reduce this happening. ATBs and/or lockers will also change how this works.

BTW - I'm not knocking autos off road. Have driven many and owned a few. But there is simply no denying an older non lockup auto is far more of a roller coaster ride on some terrain. Meaning that while you'll likely be 100%, there are more times when you become a passenger, despite sitting in the drivers seat. I see it in trials competition a lot, as many trials vehicles are autos (usually because the donor RR/Disco V8 was auto). They all go very well, but on steep and or slippery sites, you always see examples of where the lack of engine braking gives them a disadvantage. Autos when combined with lockup converters and HDC are very different in this regard.
 
Stanleysteamer said:
And for the record a/ HDC can brake each wheel individually, no driver can do that.
Click to expand...

I know how HDC works. I also know no driver cant brake an individual wheel. The original Q was not about HDC HDC? With HDC it makes no difference if you have engine braking or not its the brakes that keep you from running off.

Lets get back to you explaining how engine braking can brake an individual wheel :) Or how engine braking will slow you down, in your bog standard disco with NO diff locks, when 1 wheel looses traction/grip.

300bhp/ton said:
BTW - a wheel rotating backwards when going downhill is a function of having an open diff and lifting a wheel. With open diffs it is always a risk, but more flexy suspension can reduce this happening. ATBs and/or lockers will also change how this works.

BTW - I'm not knocking autos off road. Have driven many and owned a few. But there is simply no denying an older non lockup auto is far more of a roller coaster ride on some terrain. Meaning that while you'll likely be 100%, there are more times when you become a passenger, despite sitting in the drivers seat. I see it in trials competition a lot, as many trials vehicles are autos (usually because the donor RR/Disco V8 was auto). They all go very well, but on steep and or slippery sites, you always see examples of where the lack of engine braking gives them a disadvantage. Autos when combined with lockup converters and HDC are very different in this regard.
Click to expand...

I know.....back to the point how engine braking will slow you down, in your bog standard disco with NO diff locks :)
 
EeEk said:
I know how HDC works. I also know no driver cant brake an individual wheel. The original Q was not about HDC HDC? With HDC it makes no difference if you have engine braking or not its the brakes that keep you from running off.

Lets get back to you explaining how engine braking can brake an individual wheel :) Or how engine braking will slow you down, in your bog standard disco with NO diff locks, when 1 wheel looses traction/grip.



I know.....back to the point how engine braking will slow you down, in your bog standard disco with NO diff locks :)
Click to expand...
Mate you are off the scale.
Go away and soothe your ego elsewhere. :rolleyes:
 
EeEk said:
I know how HDC works. I also know no driver cant brake an individual wheel. The original Q was not about HDC HDC? With HDC it makes no difference if you have engine braking or not its the brakes that keep you from running off.
Click to expand...
HDC is used in conjunction with engine braking, not instead of.... :rolleyes:

EeEk said:
Lets get back to you explaining how engine braking can brake an individual wheel :) Or how engine braking will slow you down, in your bog standard disco with NO diff locks, when 1 wheel looses traction/grip.
Click to expand...
I think this just shows a complete lack of understanding on how the 4wd system works on a Land Rover. :D
 
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