 | Home > Td5 > High Low Transmission Switch |
 
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| Glynparry25 Member Since: 16 Feb 2009 Location: Miserable Midlands Posts: 3015   
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How much earlier is the new transfer box? They have been fitting the High/Low switch to 1.2 transfer boxes for about 15 years now.
The signal is a simple on/ off switch- when you select 'Low' it earths the signal from the ECU. Would it not be easier mounting a switch to a bracket that makes contact when you move the High/Low stick? Glyn   |
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27th Nov 2013 11:50pm |
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| Anderzander Member Since: 08 Feb 2011 Location: Lancashire Posts: 1000 
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Thanks for the reply !
Are you sure you're not mixing it up with the diff lock switch ? Which illuminates the warning light on the dash panel. The Hi - Low switch on the Td5's connects to the ECU, which reduces the fly-by-wire throttle pedal sensitivity when in low range, so my understanding was that this switch only came in with the TD5's ... If it was on the earlier ones, what did they use it for ? |
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28th Nov 2013 12:01am |
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| davew Member Since: 02 Jan 2012 Location: North Yorkshire Posts: 888  
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You could try it without the switch, a mod some trials drivers use is to disconnect the switch and also to disable the clutch switch. It gives improved throttle response and the anti-stall works more reliably that way.
As has been said already though it's just a switch to ground so you could easily replicate it with a switch on the dash, not checked but it'll either be a 5v or 12v "pulled high" output from the ECU, nothing special needed switch wise. http://www.yorkshireoffroadclub.net/ |
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28th Nov 2013 12:10am |
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| Glynparry25 Member Since: 16 Feb 2009 Location: Miserable Midlands Posts: 3015
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Yes, Td5 (1.4 in Defender, 1.2 in Discovery) were released in Jan 1999 just short of 15 years ago. So if it hasn't got the switch, more than likely it will be very old. What is the code on the Transfer box? Or as Dave says, just mug it off and see how things go to start with 
More information here: http://www.ashcroft-transmissions.co.uk/in...oductId=45 I am guessing you are upgrading to a 1.2 box from a Discovery 1? Glyn |
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28th Nov 2013 12:32am |
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| Anderzander Member Since: 08 Feb 2011 Location: Lancashire Posts: 1000
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Thanks. 5 or 12v was what I expected - so it may light my switch and would certainly light an LED. The motivation for a dash switch was that I've driven tracks where there is a lot of bounce that makes holding a steady pedal difficult, and I imagined with the high range map on the pedal that may have a worse effect. Interesting about the clutch switch - I hadn't been aware of that before - I'd felt it, but googling it has made for some interesting reading. I can see how they both might help the anti-stall: the higher map giving quicker pick up of revs coming off the antistall / tick over (presuming with no pedal input the potentiometer maps make no difference). And the clutch switch being off presumably not over-riding the anti-stall when dipping the clutch ? It would be interesting to have both under control and experiment with them.. |
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28th Nov 2013 8:32am |
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| Anderzander Member Since: 08 Feb 2011 Location: Lancashire Posts: 1000
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Goodness me - how quickly 15 years pass ! The Td5 still seems new to me, but your right it is old now. I've seen the Ashcroft resources - used them quite a bit when working out which D2 transfer boxes I could use - they always seem to fetch a premium though compared to the earlier ones when the only difference appears to be the high/low switch and cross drilled input gear (which I'd swap over from my existing box anyway). I haven't picked the box up yet - but it's from a Disco 1 as you say and from someone I trust (who has said its a good one). From a 300tdi I think. Stephen |
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28th Nov 2013 8:39am |
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| roel Member Since: 08 Aug 2009 Location: Lelystad Posts: 2039  
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What is the effect off disconecting the clutch switch? Roel
1984 90 2.5 na Diesel - RR V8 (1994-2001) 1997 Camel Trophy Discovery 300TDI (2001-2009) 2005 G4 Discovery III 4.4 V8 (2008-2018) It's gone but it still hurts. 2003 90 Td5 (2009-now) |
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28th Nov 2013 10:10am |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6608 
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The low range switch is an earth path switch TO the ECU, not a feed from it.
Use a double-pole switch and wire your warning light from the other pole. Don't use the ECU's input to try and wire up a warning light.  1988 90 Td5 NAS soft top
2015 D90 XS SW |
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28th Nov 2013 10:13am |
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| Anderzander Member Since: 08 Feb 2011 Location: Lancashire Posts: 1000
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Thank you Martin !
I'll have a look for a suitable pair of switches and think of a spot for them. |
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28th Nov 2013 1:45pm |
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| davew Member Since: 02 Jan 2012 Location: North Yorkshire Posts: 888
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As Martin says, it won't be suitable for driving a warning light, the pull up is likely to be very weak and current limited and also the switch will pull the output low so no power at all when the switch is activated.
You could use a diode to prevent feedback to the ECU and then have the warning light earth switching, that way you could use a single pole switch. There may even be a diode already in that circuit inside the ECU box but unless you know for certain I'd add another one !
The clutch switch does two things (or the ECU does them in response to the switch), it stops the anti-stall kicking in and reduces the power output of the engine. Anti-stall works really well on the TD5 but is often switched off by the user covering the clutch pedal in case it starts to stall or they're preparing to change gear. Disabling the switch stops the user accidentally disabling the anti-stall and also allows you to get full power on earlier. It can make "spirited" gear changes a bit more vicious though ! When fitting an auto box with Compushift or similar you can use a relay to simulate the clutch switch so as the gearbox changes gear it can "tell" the engine ECU via the clutch switch input to back the power off as the gear change happens, giving a smoother shift at high throttle positions. I believe the Disco 2 auto gearbox controller does this too. http://www.yorkshireoffroadclub.net/ |
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28th Nov 2013 2:27pm |
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| Anderzander Member Since: 08 Feb 2011 Location: Lancashire Posts: 1000
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It seems using the clutch or the throttle to come off anti-stall is a point of weakness: When the anti-stall starts to struggle pushing the clutch to get another gear is cutting the fuelling at the worst time - also though pushing the throttle at that moment to build the revs quicker than the anti-stall can seems to bring what feels like a hole in the fuelling as the throttle control transitions from the ECU to the pedal. |
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28th Nov 2013 3:38pm |
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| diesel_jim Member Since: 13 Oct 2008 Location: hiding Posts: 6093 
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When I fitted the 1.2:1 box to my 110, it was a pre Td5 era one, and thus doesn't have the switch facility.
I prefer it like that anyway.... never been a fan of the low range pedal feeling... it's all nothing-nothing-nothing-ALL OF IT!!! Much prefer the high setting, so I just left it disconnected (with some tape over the end of the plug to keep poo out of it) |
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28th Nov 2013 3:49pm |
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| Anderzander Member Since: 08 Feb 2011 Location: Lancashire Posts: 1000
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I've just had a look at the wiring diagram and it looks like the clutch switch is the same ? i.e it switches an earth back to the ECU ? |
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29th Nov 2013 6:06am |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6608
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Yes, that's right
 1988 90 Td5 NAS soft top
2015 D90 XS SW |
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29th Nov 2013 10:01am |
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