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reb78

GKN Overdrive Strip Down

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Is there any way you could fit an oil cooler?

 

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Possibly, but I guess an additional pump would also be needed then.

David and I have been talking about a finned sump like the roverdrive sump for the LT230. A similar design would increase capacity and provide some extra cooling. We are thinking of doing some tests with temp probes built in to the back plate so we can get a before and after. Visual inspection of the oil would be interesting too - you can see it has worked hard after 6000 miles at the moment as it is no longer the nice red that it went in as (unlike my gearbox oil as an example).

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Certainly looks better than the one I have here.

 

Chaps, the bluing you see is done at the manufacturing stage, it appears there is a join there so they obviously heat and sweat the parts together.

 

While this thread is current, does anyone have any GKN parts they want to get rid of?

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Realy interesting thread, good write up on how you took it apart.

I've often been tempted to look at getting an overdrive and this has rekindled that thought, although as said above the roamerdrive at £1,600 quickly puts cold water on that idea. I can't find any new GKN units for sale, so I presume they are no longer made. When were these in production?

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went out of production a few years ago, GKN sold all the spares to Devon4x4, they can rebuild a used unit but not sure if they can supply a brand new unit. bought mine 2nd hand back on 2005 IIRC. 

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If I was spending the money on a brand new overdrive it would be a Roamerdrive now. My GKN has been pretty good, but i have heard of others (on here) who have had nightmares with theirs.

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I still have a Roamerdrive if you want one Rich... :ph34r: (And a GKN....)

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46 minutes ago, reb78 said:

If I was spending the money on a brand new overdrive it would be a Roamerdrive now. My GKN has been pretty good, but i have heard of others (on here) who have had nightmares with theirs.

I have to say I've been reading this with interest as I've got the Roamerdrive, and it does kinda confirm my bias that the Roamerdrive is a much more robust unit. No friction clutch, actuated by a lever, shares oil with the LT230 and works in any gear forward or reverse, etc. etc.

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I think I recall that the early Roamerdrives had the odd issue with oil flow, but I really cant recall if I read that once or not, but you dont hear of many issues and it has to be a more robust unit by design I think. I know Neil used to leave his engaged all of the time whereas the speed sensor on the GKN was partly to prevent engaging in reverse (unless you get to 30mph in reverse) and also to stop engaging in low gears where high torque is going through the unit (not sure this will work in low range though).

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The early ones did.. They added a hole in the plate that connects it to the LT230 to improve the flow out of the Overdrive...

(I'm guessing it made the oil pumps' work a little easier and improved flow.)

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3 hours ago, V8 Freak said:

I still have a Roamerdrive if you want one Rich... :ph34r:

Is that possibly for sale on the open market?

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Haven't touched my GKN OD since removing it a while ago, think this week I'll strip it now there is space on my workbench & find out what I need to get it working again.

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Post up any questions Ralph. It’d be worth replacing the four springs whilst you’re in there. IIRC, yours was slipping? These seemed to be the issue on Neils. 

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Just made a clear work area on my bench, first job will be an exterior clean.

Yes it was slipping when engaged & disengaged, which made me think it was the vehicles clutch, which if yourememberhad me shifting the main gearbox a few times. 

I was looking at Deven4x4 GKN parts pages earlier just to see that the clutch unit has dropped in price a bit, or I've got this link https://www.overdrive-repairs.co.uk/buy-spares.php?cat=J Type Spare Parts List

6th row from top, they do exchange unit to, 

so with new springs & clutch & gaskets hopefully I can refit it again. really miss using the OD on long trips.

 

are you in cornwall permanently now ? 

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Overdrive Repairs are much better on cost than D44 but they dont stock all the parts we need for our variant of the overdrive at times so i use both companies. 

 

I bet you’ll find the clutch material looks ok. Its naturally very thin. 

 

Not down permanently yet. It’ll be another few years of travelling back and forth to London each week with the current plan! Just about to set off now! 

Edited by reb78

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once its been cleaned.,looking to strip the OD tomorrow evening after work,

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On 7/29/2018 at 9:34 PM, western said:

once its been cleaned.,looking to strip the OD tomorrow evening after work,

Where are the pics Ralph?!?!

Edited by reb78

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Right did the stripdown of my GKN OD this afternoon, took these pics, its a bit black oily inside & found one part in various pieces when it should be in one piece. had a look on Devon4x4 GKN parts pages, they haven't got a new part of my busted one, so maybe its dead as a dodo. 

 

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the 4 springs are intact, as is the clutch friction material, still got to remove the filter but don't know how it comes out, 

 

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IMG_2291.thumb.JPG.b7e67c37222502a42f56f03c29b0d8d9.JPG

 

I had the same difficulty trying to extract this circlip, think I'll need a new one to fit it all back together, 

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I think that ring sits inside the sprag gear Ralph. (I always thought the planet gears were the three that rotate around one another - they look fine in your pics)

I think D44 have some broken GKN units that they will sell spares from so it is worth contacting them for this part. Martin Kingdon (I think the name is correct) is the person to talk to.

And if you do get it working, change that oil more frequently!!!! That's way to black and gungy! Mine gets fresh oil every 6000 miles. The HP filter (and i reckon you would be wise to change it looking at how black that oil is) is cheapest from overdrive repair services - but you may just want to get it with the gaskets from D44. I have a list of gaskets somewhere, but I wont be able to copy it until Saturday.

Edited by reb78

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Hi Rich, No rush, :)

I've sent Devon4x4 a email asking --- 

if the sprag outer ring is avaiable, [busted item sits under the bronze thrust washer, which can be seen in centre in your photo copied below 

IMG_2260.thumb.JPG.c9ce424093a7c3202dae47d777738e21.JPG

& sits around the outside of the gear marked A -- in centre in this photo & the large diameter outer ring marked B -- is that swaged on or clipped in place some how ? 

 

IMG_2274.thumb.JPG.0e3b9e0d221a89736d622f9951b5754f.JPG.d3fd1ae3436663410ee149d5414e36f3.JPG

 

how the 3 planet gears come out,  [1 is seized & 1 has a tight spot, the 3rd runs fine, all the teeth & the outer ring they run on are fine, no damage]

if there is a bearing kit for the 3 planet gears. one shown here 2nd down in righthand column but noted as for a 'J ' type OD https://www.overdrive-repairs.co.uk/buy-spares.php?cat=J Type Spare Parts List

hopefully I'll have a email reply tomorow. 

how does the filter come out ?  I haven't got any info on that. 

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The filter is under one of the circular dashpot sections at the bottom of the pump (sump end). I think it is the larger of the three from memory. The centre one allows access to the oil pump piston and the other one is a pressure relief valve I think. You will need to make up a tool to insert into the holes in the circular section then undo them (normal thread) and the filter and a small gasket is all that is in there. When we took the one off of Neils, we used a couple of allen keys or screwdrivers wedged in the holes and some pliers - it was tight though so a tool of some sort would be more elegant!

 

ETA - the filter you need is third down on the left column on your link. I think D44 were asking £55 for this when i last looked, so the £10 from ORS makes them seem a bargain!

Edited by reb78
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Ah cheers for the info on filter access Rich, I'll pull that out,  going to get a bucket & more cleaning fluid to wash all the big bits in, 

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