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GKN overdrive

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No, its a SIII suffix a-c 3rd/4th synchro unit, at least in the Series version, and they're supposed to be internally similar, with just the front end different to the Defender version.

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No, its a SIII suffix a-c 3rd/4th synchro unit, at least in the Series version, and they're supposed to be internally similar, with just the front end different to the Defender version.

Now I remember where I read it. It was on your site. ;)

Eric.

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This might also be of interest as it shows a homemade tool to replace the L354A to remove the pump cover and high pressure filter cover.

It also shows that the Americans run the J and G series overdrive behind some seriously big motors and the bigger sump they use to counter the cooling problems with the oil.

http://www.ford-trucks.com/forums/1259386-gearvender-deep-sump-installation-tutorial-maximum-overdrive.html

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This might also be of interest as it shows a homemade tool to replace the L354A to remove the pump cover and high pressure filter cover.

It also shows that the Americans run the J and G series overdrive behind some seriously big motors and the bigger sump they use to counter the cooling problems with the oil.

http://www.ford-trucks.com/forums/1259386-gearvender-deep-sump-installation-tutorial-maximum-overdrive.html

Now, that bigger sump is a great idea! Thanks for posting this. I have been wondering about getting something made for my OD. I am convinced that the majority of the problems with these develop because of overheating of the oil and the long (55,000km) manufacturer recommended oil change interval. I change mine at every service (every 6k miles) and the ATF that went in still comes out looking brown a lot of the time. If i left it the recommended 55k km it would look awful. Ultimately, the unit only takes about 700ml of ATF and the cooling capacity is dreadful. I already have the extended sump on the transfer box in an attempt to increase cooling of the adjacent bit of the transmission but i don't think that's enough to directly have much effect on the GKN OD.

My only issue with those extended sumps might be that the exhaust is quite close to the base of the OD - this wont help with cooling (although i doubt it has a major effect whilst moving and hence whilst the OD is working), so i would need to check the sump wouldnt foul the exhaust.

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Wrap that section of exhaust in heat wrap and make up a big sump with cooling fins. I had heard the same thing, that most of the GKN issues are from cooking the ATF.

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I wonder how many of them get serviced properly,it is a pita to take the plate off,clean the magnet,wash the strainer,wait for it to stop dripping and refit. Also if many garages even know what it is and that it has a service requirement... Can't imagine a main dealer even knowing what it was.

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I wonder how many of them get serviced properly,it is a pita to take the plate off,clean the magnet,wash the strainer,wait for it to stop dripping and refit. Also if many garages even know what it is and that it has a service requirement... Can't imagine a main dealer even knowing what it was.

Most Defenders and Series vehicles are not serviced properly, so little chance for a fiddly and time consuming accessory like this.

The Rover/Roamerdrive, though, is fit and forget - it exchanges its oil with the transfer box (both variants), so does not alter the service task at all (except, arguably, an increased quantity in the Defender instance if you fit the bigger sump on the LT230 which replaces the normal lower cover). Since the oil is shared and rotated through the transfer box, it gets an opportunity to cool, which is helped by the replacement transfer box bottom plate which is made of aluminium and has cooling fins, so sheds heat and seals better too. The LT230 version also significantly increases oil capacity by acting as a sump.

On initial installation, you add 1/2l of oil into the unit to "prime" it (not a matter of priming any pump, it's just making sure it isn't run with dry bearings), then leave it running with the transfer box in neutral but gear box in gear for a few minutes to move the oil about and let the levels work themselves out. A quick level check after that is a good idea, but it shouldn't need any more, and that's it. There is no need to repeat on service oil changes unless you have removed the overdrive. An occasional greasing of the rose joints and pivot on the lever assembly is a good idea, but that's all it needs.

I know which unit I'd go for if I had a Defender!

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I wonder how many of them get serviced properly,it is a pita to take the plate off,clean the magnet,wash the strainer,wait for it to stop dripping and refit. Also if many garages even know what it is and that it has a service requirement... Can't imagine a main dealer even knowing what it was.

There is also a second filter behind one of the circular inserts you can see with the sump plate removed. This rarely if ever gets changed, although the couple i have looked at have seemed fairly clean.

Soutie and I have emailed the sellers of the deep sumps. I'm also chatting with David (vulcan bomber on here) as to whether we can easily make one easily.

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There is also a second filter behind one of the circular inserts you can see with the sump plate removed. This rarely if ever gets changed, although the couple i have looked at have seemed fairly clean.

Which one is it behind?

post-18025-0-92716000-1460806628_thumb.jpg

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whichever unit I would be using full synthetic Redline , as it handles greatly increased temp without degradation . JMHE

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As per the TR6 manual it seems to be the bottom one.

I can't remember off the top of my head, but if you look at the orientation in your tr6 pic, it's the one furthest from that bolt near the solenoid, so would be the top one.

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