Range Rover Auto Overdrive

Hi

Hope you can help me. I've done a search on the group and not really found what I was looking for.

Now, bear in mind I have had a search through the group and found some stuff about overdrive and gear ratios and cogs spinning at different speeds and gearbox fluid getting damaged, but it either didn't seem relevant or I didn't understand. You may have to speak slowly. I may well be using the word "overdrive" in the wrong context, but I think it helps let you understand what I mean.

I have a 97 Range Rover 2.5TDi Auto which I use regularly for towing my heavy horse and horsebox. I think what I want to do is stop it going into overdrive but I don't know how to. It goes into overdrive then won't accelerate or pull as well as it did before. Similar to my old disco I suppose - never really used 5th gear when towing. Also, it gets a bit hot at times and I didn't really expect that - I have been up and down to Edinburgh (I'm Aberdeenshire) a few times recently and there's several long long climbs and it gets really hot. I either slow down for a bit or if struggling up a long hill, I open the windows and put the heater on ;o) and it cools down again.

Does anyone know how I stop it going into overdrive? Is there a handy little switch I didn't know about, or does it involve buying some sort of shift kit? Is the overheating something I should be really concerned about? Maybe I should be simply driving in "3" and not "D" when it does that. It seems to slip into this overdrive thing quite easily.

Any help most gratefully appreciated. Cheers, Linda

Reply to
LindaMcK
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Hi, Linda. What you're experiencing is the clutch unit within the torque converter (the bit that connects the engine to the gearbox) engaging. Landrover recommend that you tow in "3", not "D", due to the pulsing from the engine that is transmitted into the gearbox when this "lock-up" clutch is engaged. This pulsing has been known to cause the flex-plate (bit that connects the torque converter to the engine) to crack and fail. It can also cause premature wear within the gearbox itself. The reason for all this is that the 'box is designed in the knowledge that the hydraulic drive of the torque converter damps out all these pulses. For the time being tow in "3", unless on a light throttle i.e. downhill or with a tailwind. Your box can be modified fairly easily (removal of sump pan and modification to control valve block assembly) to stop the converter clutch from locking in 4th gear, but it's a permanent mod and will stop it from locking all the time, bad for economy when not towing. If there was a method of making it selectable, I'd have one on my 110 3.9 auto by now! Keep meaning to look into making a selectable unit, but I never seem to have the time! Badger.

Reply to
Badger

Thankyou very much - it even made sense!! Thanks. My first pony was called Badger...

;o)

Cheers, Linda

Reply to
LindaMcK

On or around Tue, 23 Sep 2003 17:32:16 +0100, "Badger" enlightened us thusly:

[and more snip]

mine (before and after gearbox transplant) locks up at about 50. With a large trailer I'm not often doing that speed.

Reply to
Austin Shackles

Mine locks at 38mph!!!! Due to fact that my autobox is from a pre-production 3.9. Landrover figured that it wouldn't be a problem with the extra torque. Great for economy but I'd rather it was selectable for when I'm towing. Badger.

Reply to
Badger

On or around Thu, 25 Sep 2003 21:11:45 +0100, "Badger" enlightened us thusly:

interesting. The one I've just fitted is a Rover genuine parts recon which was allegedly from a 3.9, and is back to lock-up at 50 same (or nearly so) as the previous box from a 3.5i.

Mind, even at that speed it still drops the revs under 2000 when it goes in, and if you put yer toe down a bit, it jumps back to 3rd. Toe down a lot and it goes down to 2nd, of course :-)

Reply to
Austin Shackles

With a '97 I'd hazard a guess that you have the ZF 4 speed with electronic controller...

In addition to the hydraulic control it is also controlled by an ECU. I know of a challenge competition vehicle where this ECU was replaced with a programmable unit where the "lock up" could be controlled either to stop it all together or to lock it up at any speed, in any gear.

So, if you have an electronic version then it is possible to fit a fully switchable lock up but it would take some doing. IIRC (it's a couple of years since I played with one of these and the manuals aren't to hand) the lock up is achieved using a PCM signal to the box, normally derived from a speed sensor. If you were to disconnect that signal from the box with a switch it would stop it locking up. BUT depending on the output circuitry of the ECU you may end up damaging the ECU when you operate the switch.

Gear selection is done very simply, in the electronic version, using just three signal wires. You can quite simply create a fully manual ( clutchless) box by using a gear lever and a few microswitches.

The box will run hotter when not locked up BTW.

cheers

Dave W.

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Reply to
Dave White

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