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lt230 overdrives


Tonk
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how strong are the lt230 overdrive units? rocky mountain/gkn etc? do they normally wear out (if so, wot sort of mileage) or break?

considering my 'unique' driving style, would one last if i fitted one?

tia

Mark.

FYI, Dave Haines broke the one in his Ibex behind a 2.8 tgv in under a year.

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To be fair since getting the TGV Dave has done the OD, gearbox, transfer box, propshafts... so it's not just the OD being weak.

No OD but I did a gearbox, a t.box, and a front prop along with a few CVs since the 2.8 went in. Hmmmm, is there a trend developing here??? ;)

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ODs are not behind the t. case. They are between the gearbox and t. case. I'm quite sure GKNs are only supposed to be used in the higher gears. I'm not sure if Roverdrives say this, but they do say "At the present the DX Roverdrive is only available for 4 and 5 cylinder models as tests on V8 powered Land Rovers have not been completed."

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1 The GKN overdrive fits onto the back of the transfer box.

2 The GKN overdrive is not a splitter gear in that sense as the ratio in over drive top is higher than top gear.

3 The GKN overdrive will disengage at speeds of 30mph or less due to the optical sensor fitted.

4 AFAIK the GKN overdrive is a normal epicyclic gearbox.

5 Basically the GKN overdrive unit is just an up-dated version of the Triumph 2000 overdrive.

6 I use my GKN overdrive as a 6th gear.

miike FOAK

Knickers

I can cause trouble in an empty house !!!

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had my GKN for 62k miles on the back of 175bhp td5 and speed sensor failure aside no problems to date (touching wood)

they are meant for High range use and really 3rd above eg 3rd + overdrive. i think one of the reasons for the speed sensor on them (which i guess you want to bypass?) is to stop 1st + overdrive or 2nd + overdrive where torque coudl be too high.

on mine 3rd + overdrive = 4th for rpm (or near as damn it) and same for 4th + O/D = 5th. only benefit of using as a splitter gear would be quicker change under power, but you dont actuially get the splitter!

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Mine's used a a splitter gearbox mainly in 4th & 5th, it can be used in 3rd but not when putting lots of power/torque through it, in 5thODif I need some more revs for overtaking/climbing a long hill I just drop the OD out & re engage when back on the level. otherwise as JST & Mike have mentioned ^^^^^^^^ :D

Provided it's [GKN unit] isn't abused/required to perform well outside it's abilities, it should last a long time, just carry out the oil/filter service when needed.

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1 The GKN overdrive fits onto the back of the transfer box.

Yes the overdrive bolts on to the back of the t/case, but I think what Red90 was alluding to is that the overdrive only sees gearbox torque, not t/case torque because it takes its drive from the gearbox mainshaft.

I don't think Rocky mountain have updated their website for some time. I recall a couple of years ago that they claimed the overdrive for V8's was still undergoing testing.

Bill.

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  • 14 years later...

Hi to you all. I'm new here on this forum, been looking around for a bit and ended up on this old thread.

I'm interested in fitting an overdrive to the lt230 on my Td5. I have a hydraulic pump fitted on the back and am therefore looking for an OD that can be fitted to the front. Is this at all possible? 

Best regards, Ron

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Welcome Ron,

If you've got a PTO fitted to the transfer box then there's no other (easy) way to fit an overdrive. You might find it easier to convert to a crank-driven pump using either belt, chain, or shaft from the front crank pulley, freeing up the overdrive space. However, depending on your vehicle, it may be easier and a lot cheaper to just swap a higher ratio LT230 in and not have an overdrive.

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Thank you both for your quick reply. That's what I was afraid of. 

I have already been looking into the Ashcroft TB. Mine has developed a very rare sort of oil leak 😜 which probably no one has ever heard of😆... It seems to be the most economic option of the both as well. 

The 1.2 seems to go for the same price as the standard, so I guess that will be the one. 

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10 hours ago, Rondriel said:

Does anyone btw have experience with this ratio driving fully packed with trailer in mountainous areas (Norway)? Will climbing be of any problem? 

Hi Rondriel, 

A 1,2 is quite a bit tæller in gearing, and if your td5 is stock, I would not recommend it! 

I have a tweeked 300 and it strugles when in "camping mode" and even more when a trailer is connected at the same time. 

My parrents have a 90 td5 with a mild tweak and although it copes, 1'st is to high, and a lot of gearchanges between 4/5 is nedded to keep things going. At one long trip where we just kept it going in 5'th it caused the main gearbox to devellop a bad noise (oil being to hot). 

BUT the light loaded Cruise becommes more pleasent! 

/mads

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On 8/24/2021 at 8:48 PM, Rondriel said:

Does anyone btw have experience with this ratio driving fully packed with trailer in mountainous areas (Norway)? Will climbing be of any problem? 

Is it a fully packed 90 or 110? Small camping trailer or 3.5t box trailer?

The 1.2 ratio gives you the same gearing as a Discovery 2 which also had the TD5, but smaller tyres as standard... but Discoveries are heavier than Defenders and they tow stuff around all the time and seem to do fine...

Usually 1.2 transfer boxes from old RR/Disco are cheap and plentiful so it's a (fairly) easy experiment to swap one in and see how it goes.

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12 hours ago, FridgeFreezer said:

Is it a fully packed 90 or 110? Small camping trailer or 3.5t box trailer?

The 1.2 ratio gives you the same gearing as a Discovery 2 which also had the TD5, but smaller tyres as standard... but Discoveries are heavier than Defenders and they tow stuff around all the time and seem to do fine...

Usually 1.2 transfer boxes from old RR/Disco are cheap and plentiful so it's a (fairly) easy experiment to swap one in and see how it goes.

Hi, 

Your right, but the disco also had some 20 more hp 😉

I totally agree, a swap to check if it suits is easy.

/mads

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My 110 is fairly regularly towing 3.5t on steep gradients (the flattest exit from my house to the main roads has a 1 in 3 on it) running a 1.2 ratio on 265/75R16s.

Apart from 1st I actually prefer the 1.2 box for towing. It may be subjective to UK roads but I've found the 1.2 on 32" tyres puts the gears in a more sensible place, 60mph in 4th is perfectly comfortable. I've found it sits in the power band on a Tdi far more effectively than with the 1.4 box where I was always chopping and changing between gears.

But the very tall first is a pain in the backside but nothing a judicous amount of clutch slippage can handle. I've got a 130 clutch fitted to mine and when I rebuilt the engine a couple of years back the clutch which had 80k of hard towing and clutch slippage was absolutely fine.

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