The GKN Overdrive

[reb78]

1 hour ago, Little mule said:

My friend mentioned this as well . They are either in and out the same end or a through and through. I’m thinking the shifting piston might be the same thread and some parts might fit.

he also mentioned that he had one that was shifting in and out on its own . He took it apart and found the “O” rings were worn out on the internal pistons . He replaced them and it worked very well.

we might find or be able to find parts this way rather than paying the arm and leg price from known dealers. 
 

I’ll take a look at one or two of them this week when I have some time . 
the shift button on the shifter and wiring might be a little more robust than the GKN version 

Tony 

Overdrive rebuild services in sheffield sell parts for the laycock type overdrives. A lot of the bits they sell for the J type are compatible with ours. But there are some defender specific bits they dont sell.

 

https://www.overdrive-repairs.co.uk/product-category/j-type-spare-parts/

 

Always better priced than D44 on everything too. 

[Little mule]

Thank you for the information on this site . It’s always nice to have a place where you might be able to get some parts.

I really appreciate the scale and scope and everyone’s advise on everything I have learned and read on this forum 

thank you everyone 

 Tony 

[Ibex94]

4 hours ago, Little mule said:

Thank you for the information on this site . It’s always nice to have a place where you might be able to get some parts.

I really appreciate the scale and scope and everyone’s advise on everything I have learned and read on this forum 

thank you everyone 

 Tony 

Also look out for @vulcan bomber, he's now got his own gasket set, bearings and main seals, only a matter of time before he's got a kit of o rings.

[reb78]

47 minutes ago, Ibex94 said:

Also look out for @vulcan bomber, he's now got his own gasket set, bearings and main seals, only a matter of time before he's got a kit of o rings.

The beauty of what @vulcan bomber is doing is that he is developing bits for the defender GKN ODs specifically and looking at how to fix a number of their weaknesses. 

[Oakmaster]

8 hours ago, reb78 said:

The beauty of what @vulcan bomber is doing is that he is developing bits for the defender GKN ODs specifically and looking at how to fix a number of their weaknesses. 

I expect that for @vulcan bomber and all of us if we could somehow get a picture of how many units are out there?  Total, working and non working - it seems quite a few of us have more than one?  

 

[Little mule]

I’m not sure if mine works lol it better it is brand new lol.

[vulcan bomber]

My hope is that a lot of what i plan to do will also improve the units for the guys using them on stuff other than the Land Rovers. But i'm concentrating on the Land rover one because they seem the least reliable.

I've just ordered some more Gasket Paper so i can get a batch of gaskets cut.

I can already supply the large Bearing and the 2 oil Seals for the adaptor plate, the seals are an upgrade being twin lipped and made of viton to withstand the high temps around the units and needing 3 lips to fail before the oil starts mixing, with the standard seals its only 1 lip that needs to fail and this does appear to be a common issue with the units, we know they dont like EP90. I can sell you a pair of these for £22 where devon sell you one standard seal for £19.19.... A seal i can source for about a quid.

 

If any of you are farcebook users, i've set up a page on there for these units.

 

[Oakmaster]

here is a link to a thread on Facebook - started 6 years ago:

https://www.facebook.com/search/top?q=gkn overdrive

 

 

[western]

 

Vulcan Bombers group page 

https://www.facebook.com/groups/3515534132009573/?ref=share

[Little mule]

I’m not really on face book accept for my wife’s games . I’ll join the group later today what I have some time .

[Little mule]

If someone were to build a spacer plate to lower the over drive sump to clear the bigger Tcase sump . How deep would it have to be 3 to 4 inches ? Maybe more or less ? 
if some one has both parts available in their shop would it be possible to do a quick measure to see what it would take to have a spacer plate made to lower the MO deep sump.

thanks everyone for their help

Tony 

[Sigi_H]

I would rather build an external tank with an electric pump. The filler opening can be used as a suction connection for the pump. It presses into the external tank and from there an overflow flows back to the OD. The rev sensor offers itself as a return.

[Sigi_H]

When the el. pump is controlled by a temp sensor this will work as a cooling too

[western]

6 hours ago, Little mule said:

If someone were to build a spacer plate to lower the over drive sump to clear the bigger Tcase sump . How deep would it have to be 3 to 4 inches ? Maybe more or less ? 
if some one has both parts available in their shop would it be possible to do a quick measure to see what it would take to have a spacer plate made to lower the MO deep sump.

thanks everyone for their help

Tony 

This what VB is working on. 

[FridgeFreezer]

5 hours ago, Sigi_H said:

When the el. pump is controlled by a temp sensor this will work as a cooling too

This sounds like adding points of failure to me.

[Sigi_H]

7 minutes ago, FridgeFreezer said:

This sounds like adding points of failure to me.

It depends on the quality of the construction. The entire OD is an additional point of failure. Therefore, the best solution is an LT230 with a longer gear ratio.

[vulcan bomber]

8 hours ago, Little mule said:

If someone were to build a spacer plate to lower the over drive sump to clear the bigger Tcase sump . How deep would it have to be 3 to 4 inches ? Maybe more or less ? 
if some one has both parts available in their shop would it be possible to do a quick measure to see what it would take to have a spacer plate made to lower the MO deep sump.

thanks everyone for their help

Tony 

The Exhaust is in the way.

 

[vulcan bomber]

37 minutes ago, Sigi_H said:

It depends on the quality of the construction. The entire OD is an additional point of failure. Therefore, the best solution is an LT230 with a longer gear ratio.

Its not, it affects all the gear ratios.

[Sigi_H]

22 minutes ago, vulcan bomber said:

Its not, it affects all the gear ratios.

So what? 😃

I had an OD before and now a 1.1 LT230 on the LT77

The 1.1 is a lot easier to handle. The only difference is, that I use 4 gears most of the time.

[vulcan bomber]

5 hours ago, Sigi_H said:

So what? 😃

I had an OD before and now a 1.1 LT230 on the LT77

The 1.1 is a lot easier to handle. The only difference is, that I use 4 gears most of the time.

My 110 got a 1.2 transfer box for 5 days before I decided I couldn't tolerate it. 1st is to tall and 5th is all but useless. That's attached to a 200TDi that's had the wick turned up significantly and will pull to 85 and beg for another gear. Imho changing transfer box ratios is a bodge.

[Little mule]

I have been around rovers for over 30 years . I have been down the engine conversion thing . The high ratio box thing . The change the gear ratio in the axle change thing and I’m pretty sick of figuring out what I wanted . 
 

 This is what I’m looking for . A strong 300 rover tranny and transfer box with an over drive . 
I’ve been collecting these parts for the past while knowing what I have been looking for . I have a beautiful rust free two door .

Now it’s time to get the drive train sorted . 
 

just looking for some advice is all 

 

[Sigi_H]

The only real way to decide is to calculate speed vs revs in every gear. Every ratio including tyre size is important, also the average weight of the car. Tuning of the engine too.

If one can´t do it by himself, the ratio calculator from Ashcroft is a good solution.

Mule found his decision and it is not a bad way to do it. I just wanted to offer another perspective, not meaning that this is the one and only.

My way is very good for me traveling a lot. It is useless if you have to tow a lot. But you will learn, how to start in LO gear and shift to HI gear while rolling, when towing heavy loads uphill 😧. The most "anoying" difference is, that in narrow corners in cities and villages I have to use first instead of second gear.

Especialliy my old OneTen is a lot quieter in 5. gear. I can use it from 80 km/h. Motorways are a dream. The first time I can hear music without OD 😁 Below 80 the car runs like with a 4 gear box. But even TD4 drivers are surprised about the slightly tuned 200tdi with long LT230. I am really happy with it, because I allways had problems with the OD. Everything is so easy now. No more extra oil changes, no self shifting, less weight.

 

 

[Kozzy]

 

Seen this on ebay a few weeks ago, can anyone tell me what is that oil sump extension ? mine doesn't have that.

[Little mule]

That over drive looks like it’s got a deep sump on it . 
I live in a very hilly part of the country and having the ability to split gears is what I’m looking for .  
if someone has a GKN installed and has a measurement of the distance I might be able to get some one here to have a look at doing something . Measurements between the exhaust and so on and maybe a pic or two . 
I know a cpl of really good machinists in the club who would love nothing better than to tackle something like this .

And im sure bomber will come up with something 👍

[reb78]

1 hour ago, Little mule said:

That over drive looks like it’s got a deep sump on it . 
I live in a very hilly part of the country and having the ability to split gears is what I’m looking for .  
if someone has a GKN installed and has a measurement of the distance I might be able to get some one here to have a look at doing something . Measurements between the exhaust and so on and maybe a pic or two . 
I know a cpl of really good machinists in the club who would love nothing better than to tackle something like this .

And im sure bomber will come up with something 👍

Just a note - people speak of these ODs as splitters but 3rd plus OD is pretty much 4th and 4th plus OD is pretty much 5th etc... - thats on the LT77 and R380. The plus OD is ever so slightly lower than the next gear up but not a lot. Mine is basically a 6th gear that allows me to retain the original 1st gear ratio.  

Edited August 30, 2023 by reb78