The GKN Overdrive

[Snagger]

4 hours ago, robperrie said:

i also looked at the roamer drive a few years back and read that the use of inferior parts they have been unreliable too...why change something when it works.

Because Britpart, though in fairness, Roverdrive used carp bearings right from the start.  I can see why they made the unit more compact with later versions, but it doesn’t appear to help longevity.

[reb78]

5 hours ago, Snagger said:

Because Britpart, though in fairness, Roverdrive used carp bearings right from the start.  I can see why they made the unit more compact with later versions, but it doesn’t appear to help longevity.

Dont think we can really blame Britpart for this one! I never thought i would ever defend them!

[reb78]

9 hours ago, robperrie said:

good morning, ive had my gkn for about 100k so far, yes , had to totally strip it down a few times and clean it and replace some bits, now also looking for a speed sensor and maybe a clutch, it had a hard drive to malaga with 4.5 ton on the back, been ok though the last 18 months and then it started to slip the other day, but when i carried on using it, it stopped slipping, weird, but my lights flashing like a good un, if i go below 50 it cuts off, so im guessing now the speed sensor has given up, i also looked at the roamer drive a few years back and read that the use of inferior parts they have been unreliable too...why change something when it works.

It might be simplest to bypass the sensor. Then you just have to remember when not to use it. 
 

For the cone clutch, overdrive repair services in Sheffield sell the right part at a reasonable price. 
 

Slipping may not always be the clutch though. Ralph has a thread on here and I suppose, it was really poor pressure on the rear pistons that caused the clutch to slip (Ralph?)

[western]

1 hour ago, reb78 said:

It might be simplest to bypass the sensor. Then you just have to remember when not to use it. 
 

For the cone clutch, overdrive repair services in Sheffield sell the right part at a reasonable price. 
 

Slipping may not always be the clutch though. Ralph has a thread on here and I suppose, it was really poor pressure on the rear pistons that caused the clutch to slip (Ralph?)

Not sure for definite, my rebuilt GKN is still sat on the bench in my garage, hopefully get it refitted after Xmas. 

But the slipping was definitely caused by the OD as when it was removed the slipping ceased. 

[Snagger]

1 hour ago, reb78 said:

Dont think we can really blame Britpart for this one! I never thought i would ever defend them!

As the sole distributor, they can lean on the manufacturer to source parts from favoured sources, or more often, cheaper sources.  But mine was built before that happened and still had awful, unbranded Chinesium oval bearings.

[reb78]

2 hours ago, Snagger said:

As the sole distributor, they can lean on the manufacturer to source parts from favoured sources, or more often, cheaper sources.  But mine was built before that happened and still had awful, unbranded Chinesium oval bearings.

Yeah. I suppose, but as you say, they had chocolate bearings from the outset. It just matches britparts usual quality i suppose. 

[Snagger]

On the plus side, Tim’s and my units proved to be much easier to fix than poor old Ralph’s GKN, even with all the fiddling to get that hard to reach internal circlip out, and have been reliable since.  Roverdrives do have simplicity on their side, so once they get decent bearings, they should be trustworthy units.

[reb78]

I think that figuring out the problem with Ralphs unit was the hardest part. Hopefully its fixed now! I have one with similar symptoms to Ralphs so if his fix works I can ask @vulcan bomberto repair my spare. 
 

I have said it a lot but I think the GKN suffers from poor maintenance - if you follow GKNs instructions, oil changes are something like every 30k miles. I do mine every 6k miles. There is only 700ml or so of ATF in there and it gets very hot in use. It will never last the specified interval by GKN. 

Edited December 6, 2022 by reb78

[Little mule]

Hi everyone .

this topic is very interesting to me.

I have a brand new GKN over drive in my shop still in the box ready to install.

my Goal is to install it into my 1990 RRC 2 door. Here in Canada the winters  are pretty harsh sometimes and the wires get corroded fast .

I’m thinking I won’t be installing the speed sensor because I’m the only one who drive my truck . 
Right now the old VM is a boat anchor but still starts and runs but you pour more oil into the intake than anywhere else lol.

My plan is to do up a 300 with all the go fast goodies once I have the rotating assembly balanced . The only parts that are being reused are the crank shaft and connecting rods ,but I might up grade them to fractured rods instead of the factory machines rods.

Ok back to the over drive .

has or does anyone know of a person installing the over drive onto a auto box ? .

im really not considering it but it would nice to know if it’s been done.

my truck has a LT77S rebuilt by Ashcroft and I’m ditching the B/W T-case and going to a LT 230 with 1.4 gearing . 

Both my front axle and rear are both going to be Salisbury diffs.

I found a SNATCH truck front Salisbury out of the UK and I had a rear out of a 110. Both will have true-trac,s installed . I’m still not sure if I want to go with a bigger tire or just stay with the 235,s

im also going with the softest springs I can I think are 125lb springs. I want a smooth ride and air suspension doesn’t work well here in Canada . I also have the factory load lifting unit in the back and it still works well.

The over drive takes ATF and that may be part of the problem I think. ATF is designed for pressure and allows slippage in a auto box and it burns up pretty easily.

my B/W T-case burns it up regularly if I don’t change it every 10k miles .

my LT77 also takes ATF but I changed it to Castro 5W50 synthetic engine oil . The oils is designed to lube bearings and bushings .

I have a friend that’s lived in S/A and his dad was burning up ATF and his tranny in his 110 and it was running super hot . I suggested for him to change the ATF out and install the Castrol engine oil. He did change it and his tranny temp dropped by 30 degrees and ran smoother and shifted better.

I have also done it on my LT77 and it makes a huge difference .

I wonder if this oil change solution would work with the GKN ? 

I have read somewhere you can buy a deeper sump for the GKN and it gives you a little over a liter in the reservoir .

the deeper sump also have cooling fins that are now exposed to ail flowing over them to help cool the oil .

just my thoughts .

im also very interested in anyone’s thought of things I should do and need to know before I install it into my RRC .

I’ll be going with the same setup as most 238/85/16 tires , 1.4 T-case and a five speed . 
 

My turbo set up is a hybrid rover/ cosworth Turbo with three inch exhaust all the way back .

im still trying to decide on weather on not to use the 300 disco exhaust manifold instead of the factory 300 unit . The disco manifold will keep the heat of the turbo away from the intake manifold which should increase performance and not heat soak all the inlet piping to the intake manifold .

I bought the over drive brand new 10 years ago and opened it up to get the owners manual and put some preservative on whole unit and packed it up and stored it . I hope to have it out and installed in the next cpl of years lol.

Thanks for all your info and advise I look forward to hearing from you all .

Thanks 

Tony 

ps this is my ride and those are factory wheels from Land Rover  

[reb78]

8 hours ago, Little mule said:

Hi everyone .

this topic is very interesting to me.

I have a brand new GKN over drive in my shop still in the box ready to install.

my Goal is to install it into my 1990 RRC 2 door. Here in Canada the winters  are pretty harsh sometimes and the wires get corroded fast .

I’m thinking I won’t be installing the speed sensor because I’m the only one who drive my truck . 
Right now the old VM is a boat anchor but still starts and runs but you pour more oil into the intake than anywhere else lol.

My plan is to do up a 300 with all the go fast goodies once I have the rotating assembly balanced . The only parts that are being reused are the crank shaft and connecting rods ,but I might up grade them to fractured rods instead of the factory machines rods.

Ok back to the over drive .

has or does anyone know of a person installing the over drive onto a auto box ? .

im really not considering it but it would nice to know if it’s been done.

my truck has a LT77S rebuilt by Ashcroft and I’m ditching the B/W T-case and going to a LT 230 with 1.4 gearing . 

Both my front axle and rear are both going to be Salisbury diffs.

I found a SNATCH truck front Salisbury out of the UK and I had a rear out of a 110. Both will have true-trac,s installed . I’m still not sure if I want to go with a bigger tire or just stay with the 235,s

im also going with the softest springs I can I think are 125lb springs. I want a smooth ride and air suspension doesn’t work well here in Canada . I also have the factory load lifting unit in the back and it still works well.

The over drive takes ATF and that may be part of the problem I think. ATF is designed for pressure and allows slippage in a auto box and it burns up pretty easily.

my B/W T-case burns it up regularly if I don’t change it every 10k miles .

my LT77 also takes ATF but I changed it to Castro 5W50 synthetic engine oil . The oils is designed to lube bearings and bushings .

I have a friend that’s lived in S/A and his dad was burning up ATF and his tranny in his 110 and it was running super hot . I suggested for him to change the ATF out and install the Castrol engine oil. He did change it and his tranny temp dropped by 30 degrees and ran smoother and shifted better.

I have also done it on my LT77 and it makes a huge difference .

I wonder if this oil change solution would work with the GKN ? 

I have read somewhere you can buy a deeper sump for the GKN and it gives you a little over a liter in the reservoir .

the deeper sump also have cooling fins that are now exposed to ail flowing over them to help cool the oil .

just my thoughts .

im also very interested in anyone’s thought of things I should do and need to know before I install it into my RRC .

I’ll be going with the same setup as most 238/85/16 tires , 1.4 T-case and a five speed . 
 

My turbo set up is a hybrid rover/ cosworth Turbo with three inch exhaust all the way back .

im still trying to decide on weather on not to use the 300 disco exhaust manifold instead of the factory 300 unit . The disco manifold will keep the heat of the turbo away from the intake manifold which should increase performance and not heat soak all the inlet piping to the intake manifold .

I bought the over drive brand new 10 years ago and opened it up to get the owners manual and put some preservative on whole unit and packed it up and stored it . I hope to have it out and installed in the next cpl of years lol.

Thanks for all your info and advise I look forward to hearing from you all .

Thanks 

Tony 

ps this is my ride and those are factory wheels from Land Rover  

Nice RR. I have never heard of anybody fitting a GKN with an auto. 

It will mate nicely with the 300tdi, LT77, LT230 combo. 

I run my overdrive hard in the 110. Lots of long motorway (250 mile stints in one go) and it sits nice at 80 behind my 200tdi. My experience says use ATF and change it every 6k miles - which is when I do engine oils anyway. I ha e done about 150k on my overdrive like this and it was secondhand when I fitted it. You point out yourself why the non auto suitable oils arent really right for it. My ATF will come out a little brown but not burnt at those intervals. I wouldnt leave it longer though - the factory oil change recommendations are waaaaaay too long. 

I am looking at a getting a deeper sump. @vulcan bomber is looking at making one. This will have a massive benefit IMO by increasing oil capacity and helping cool the sump oil if designed appropriately. 

[Sigi_H]

Any other oil than ATF can damage the coating of the conical clutch of the GKN. I used ATF and gear oil fifty/fifty to lift viscosity. Shifting was a lot better then ... but only for some thousand km.

The clutch coating was disolved and blocked the oil filter. When the planetary gear wasn't lubricated, it broke.

My much better solution is a 1.1 T-box behind a LT77 and a slightly pimped 200TDI. A real dream.

 

[FridgeFreezer]

Pretty sure engine oil in anything with wet clutches is a recipe for a bad day. ATF is designed for the specific purpose.

[Sigi_H]

You can't say that in general. Most motorbikes have wet clutches.

In the GKN Overdrive it is a problem!

Unfortunately it is seductive to do so, because higher viscosity solves shifting problems instantly. In my eyes it is a sign for wear in the casing. Cylinders of the actuating pistons will be worn. They even can't build enough pressure with new o-rings.

Never use anything else but ATF

 

[Junglie]

17 hours ago, Sigi_H said:

You can't say that in general. Most motorbikes have wet clutches.

 

 

And they are unit construction - the engine and gearbox (and clutch) share the same oil. As well as revving through to (on mine for example) 14500 rpm!

[Little mule]

On 8/8/2023 at 5:54 PM, reb78 said:

Nice RR. I have never heard of anybody fitting a GKN with an auto. 

It will mate nicely with the 300tdi, LT77, LT230 combo. 

I run my overdrive hard in the 110. Lots of long motorway (250 mile stints in one go) and it sits nice at 80 behind my 200tdi. My experience says use ATF and change it every 6k miles - which is when I do engine oils anyway. I ha e done about 150k on my overdrive like this and it was secondhand when I fitted it. You point out yourself why the non auto suitable oils arent really right for it. My ATF will come out a little brown but not burnt at those intervals. I wouldnt leave it longer though - the factory oil change recommendations are waaaaaay too long. 

I am looking at a getting a deeper sump. @vulcan bomber is looking at making one. This will have a massive benefit IMO by increasing oil capacity and helping cool the sump oil if designed appropriately. 

Thank for the reply.

after looking at my expanded schematic of the GKN I guess you could say it does have a hydraulic property to it because of the shift solenoid changes the flow of the fluid and apples a clutch to shift in and out of over drive . I would be interested in a bigger sump is @vulcan bomber is having some made up. I do remember looking for a deeper sump and thought the denorminville (I think that’s how you spell it) over drive had a deeper sump . This is the one they used on older Volvo,s and some NA trucks and cars used on this side of the pond . 
I bought my truck in 2010 and it can from France . It has ZERO rust. It looks like was stored in a barn or sea container for years and never exposed to the elements. 
the 2.5 VM had a head gasket leak when I bought it and I fixed that with a little magic lol from the auto supply store. It ran very well up u till the day I decided I was not letting a Toyota preius pass me on the road. I do remember looking down at the speedo and I was going 175kph and the temp gauge was in the red then I saw some blue smoke out the tail pipe . I now have extreme blow by and oil gets sucked into the air cleaner and it could runaway if I had kept driving it.
I was getting about 26mpg and I wasn’t driving it easily . I could get close to 30mpg if I took it easy. The engine had 280+km,s on it at the time and already had head work and so on. 
I has to admit it was one of the best trucks I ever bought for the money at the time . I paid $8k cad including shipping on a row row to Canada from France . Today try to find a rust free two door left hooker form under 30k and that’s if it’s in ok shape lol.

I just found this site with a gearvenders OD and they offer a deep sump for their over drives. I wonder if they would fit the GKN over drive 

https://www.nickpisca.com/diesel/engine/gearvender-deep-sump-installation-tutorial-maximum-overdrive/

I was looking an installing a OM606 but it’s way to expensive and I have all the parts here to build a super strong 300 or 200.

cheers 
 

[FridgeFreezer]

19 hours ago, Sigi_H said:

You can't say that in general. Most motorbikes have wet clutches.

...which are designed to work in their spec of engine oil.

I asked a friend in the oil industry about this - his company design & manufacture all the chemicals that go into oil to make it work, and he said that unsurprisingly it's a bad idea to use the wrong oil as they are all designed to work differently, interact differently with different materials and conditions, etc. so basically you're going to wear stuff out quicker and the oil will lose whatever effectiveness it has faster.

He does suggest Ford type F oil could be "grabbier" than regular ATF but it might also wear stuff out faster so take your pick.

[Little mule]

Sigi I did ent realism there was a protective coating on the clutch. I thought it might be built the same as. Old ferry with just a cone type clutch . 
When I was in the military we had these German jeeps called litis,s and they would start to grind during shifting . They used to run ATF in them . One of the things we had to do to make them shift better was use a Mopar product that was supposed to help with the shifting problem . It’s was a friction modifier . It was mainly used in mopar automatics to help them shift properly . I will tell you it really really stunk god t was bad. It took days to get it out of your cloths in you spilt any. I think I’m dating my self now lol . 
does running synthetic ATF make a difference ? 
I also posted a link I found on a bigger sump with this work and maybe help with cooling ?

right now I have the over drive still packed away in the box ready to go together . My LT77 is on the bench because it grinds going into 2nd weather it’s a up shift or down shift . I have a complete rebuild kit from Ashcroft . They also rebuilt this tranny about 20 years ago when the previous owner had it . Other than that it runs a treat. Once I get the old VM junk out I’m sure this truck will last me a long time . 
I want the get the best out of the drive train because my wife and I want to travel now that I’m retired from the military and we want to take the rangie as our drive around truck . We will be towing it behind our motor home on a trailer when we travel . 
 

[Little mule]

3 minutes ago, FridgeFreezer said:

...which are designed to work in their spec of engine oil.

I asked a friend in the oil industry about this - his company design & manufacture all the chemicals that go into oil to make it work, and he said that unsurprisingly it's a bad idea to use the wrong oil as they are all designed to work differently, interact differently with different materials and conditions, etc. so basically you're going to wear stuff out quicker and the oil will lose whatever effectiveness it has faster.

He does suggest Ford type F oil could be "grabbier" than regular ATF but it might also wear stuff out faster so take your pick.

I’ll have to look closely at the oil recommendations on the instructions . I have a long time friend who works at the oil refinery here on the east coast and she knows her stuff lol. If the instruction call for an oil with certain properties in it im sure she will point me in the right direction . 
the last time we had a rally she came along and had a blast . She mentioned they are working on a blend of oil for older 70,s and 80,s cars and trucks so they doing burn so much oil . They took most of the lead and zink out of the oils that helped these engines run better and not smoke as much . Some of the older engine don’t like the newer type of oils because they are too thin where as older engines like the thicker natural oils not the synthetic blends . 

[vulcan bomber]

Regards the deeper sump, I've got a few ideas pending for this but currently I don't have a GKN Overdrive fitted to a vehicle to get measurements from. The only regular GKN user I currently know is @reb78 but his 110 is awaiting a new chassis and he's about 250 miles away. He's sending me a spare overdrive up when he gets time. And then I can get the ball rolling. I've had other ideas of how to dissipate more heat from the units but first I need to get some ball park figures to start from to see how effective they are.

 

As for oil, stick to ATF as mentioned.

 

As for wear in the case, I've repaired one for @western involving machining of the case. I think with not much effort the case could be sleeved with an iron sleeve which will stand upto the use a lot better than aluminium. 

 

I've said it for a while, but watch this space.

[Sigi_H]

Many years ago I wrote this article in German.

http://www.landypedia.de/index.php/Überholung_eines_GKN_Overdrives

I'm still the opinion, that a 1.1 ratio T-box is the better solution.

My main goal was, to make the old Oneten quieter. Both methods work good, but the method with a 1.1 T-box is a lot more uncomplicated

 

[western]

Still waiting on good weather & need some time off work to get my overdrive refitted & see how it behaves. I will get to it sometime. 

[JeffR]

I have two of the buggers, one in a 200tdi 110 which has done well in excess of 200K miles and never missed a beat. used it a lot in low range when i was ecologist on M6 toll road.  Standard sump and ATF, love the damn thing.  The other lived in my previous 110 V8 for best part of a decade, vehicle was driven like it was stolen relatively enthusiastically and by my wife (quote of the century from her after a 200 mile journey on her own "what does the little oil can on the dash mean, its only been on for 80 miles"), again ATF and standard sump. Only one problem with it in that time and that was the speed sensor unplugging itself. It included driving from Penrith to Honiton in overdrive low range cos it got jammed in low range and I couldn't face trying to sort it out on the camp site.

[vulcan bomber]

4 hours ago, western said:

Still waiting on good weather & need some time off work to get my overdrive refitted & see how it behaves. I will get to it sometime. 

When I get this one of Richards fitted, if you want to send yours up and I'll run it around on my 110 for a few weeks and see how it goes. If it works you can fit it with some confidence.

[Ibex94]

Just picked up a non working unit on ebay for a steal (imo) Hope to get my hands on it at the weekend then see what I can work out.

 

[L19MUD]

13 hours ago, Ibex94 said:

Just picked up a non working unit on ebay for a steal (imo) Hope to get my hands on it at the weekend then see what I can work out.

 

if it is the one in the completed history on ebay for £21 then I absolutely agree!! I would have outbid you on that if I had seen it. Good luck and post up how you get on