[Jayce]

Hi all

I have just got my hands on a second hand overdrive unit, yet to be installed, and despite having the original manual, I am a little confused about the operation of the unit.

It is clear to me (from the manual), that to engage the unit you press the lever forward, and to disengage you pull it back. However where does the neutral position fit into all of this, or is there no such thing? :dunno:

Firstly Does the standard gearbox work as normal if the overdrive is in neutral.
Secondly, once I have disengaged the overdrive, do I have to move the lever back to the neutral postion.

My logic tells me that this should work like the transfer box i.e. its in the disengaged postion until told otherwise.

Your help would be appreciated.

Regards

Jayce

 

[jozg44]

Hello,

You've got the forward/back operation bit correct.

1) There is a Nuetral position, but there's no 'notch' for it- you just have to leave the lever somewhere between the two gears. It's not designed in, but it does exist, if that makes sense.

2) The main gearbox works as normal regardless of whether the overdrive is engaged or not- so you have in effect 16 forward gears and 4 reverse- BUT- to save over-stressing the O/D, only use it in High 3rd or 4th.

3) The O/D is either ENGAGED or DISENGAGED, there's no clever work needed.

So, in an ideal situation, you'd have this:

i) O/D Disengaged, pull away in 1st, change to 2nd, change to 3rd (as usual).

ii) Depress clutch, push O/D lever forward to engage, release clutch, accelerate

iii) Depress clutch, pull O/D lever back to disengage. Engage 4th. Accelerate

iv) Depress clutch, push O/D lever forward to engage, release clutch, settle into the 'cruise'.

Of course, you don't have to to use the O/D in 3rd as well as 4th- that's just an example of how it works. Most people just use it in 4th once they've wound up to their cruising speed to reduce noise / fuel consumption.

I hope this helped (if it made sense at all),

Jack

 

[DickFox]

So can you over stress OD? Should it not be use during towing or four wheel driving? I have used it a bit in both cases.

 

[Jayce]

Dear Jack

Thanks for the detailing the use of the overdrive. I thought as much, the nuetral position just got me a little confused. Although I must admit that the changing from 3rd OD to 4th OD, would require some deft operation of the clutch and levers or other wise the time taken to change may have dropped engine speed to the point that you have to go into second

 

[Moeras]

Stop the bus!!! I am confused!

16 gears? 4X4 = 16

Normal driving - OD not engaged = 4
Low ratio = 4
Normal driving - OD engaged = 4
That makes 12!

Unless you engage OD in Low aswell, that is another 4, but why do you want to do that?

Also, if there is a Neutral, and the gearbox works in the same way as OD not engaged then there is no neutral! (does it makes sence?) A neutral should be the same as with the transfer box, if in neutral you dont go anywhere!
Or do I have the cat by the balls?

 

[TerryS]

Moeras, I don't think you're loosing it.
Under what possible circumstance would anyone need to have another set of 4 ratios in Low Range?

Fairey, and other make overdrives are not intended to have a "neutral" position, it's only that there is a spot in the throw of the sliding sleeve where it isn't engaged, that you could say it was in "neutral. If there was an intended reason for this, there would have also been a detent to hold it there. Just the slightest movement and it will be engaged in the normal final ratio or the lowered (OD) ratio, and that's a good way to wipe out the engaging taper of the sleeve.

OD is not really intended for anything other than lowering the engine revs in 4th when you're up to a cruising speed, but often used in third only because it's about half-way between 3rd & 4th.

If you looked at the possible ratio combinations, 4 Hi-IN, 4 Hi-out, 4 Lo-In,
4 Lo-out, there are going to be so many that are so close as to not even matter. If you wanted to get technical, you could even say it's 20 if you add
R Hi-In, R Hi-out, R Lo-In, R Lo-out, but so what,with a usable engine range of 4000 rpm, who needs them all.

 

[jozg44]

Indeed, a 3rd - Overdrive 3rd - 4th change does require a similar dexterity to a concert pianist, and you have to get it right first time. As I said, most people never use it, but when towing I think it's useful to have the option of a gear between 3rd and 4th (it's quite a big gap, and when you've got 2 tons behind a 62 horsepower diesel, you need all the gears you've got).

Can I just clarify that I was not saying that the overdrive SHOULD be used in Low Ratio (or indeed any gear other than High 3rd and 4th). I agree it would be utterly pointless and would very quickly over-stress the overdrive. I was just demonstrating that the O/D is not in anyway limited to certain gears (like the more common electric over-drives found in old saloon and sports cars).

Jack

 

[Moeras]

Jack

Point taken, but you totally confused me with the 16 gears and why you would want 16!!.

In the Army I once drove a 60 ton Tank carrier and that had 20 gears (5 spead box with 4 ranges). That was enough to move a 80 ton+ 6X6 truck anywhere in most conditions and for the same truck to do 120 km/h with a full load. (And that was extreamly confusing).

Thanx

Johan

 

[Chick Magnet]

Just to go back a step, the PTO box is allways engaged. No doubt part of the kit is the replacement sprocket for the back of the gearbox.?

Therefore all the torque from the (thumping) 62hp motor goes through the PTO box before it sent back to the transfer case. There is a needle bearing on a concentric shaft that the your new sprocket runs on to account for the different Revs

My Fairy used to whine like kids when going up hill and I allways stressed about blowing it up as there is no "limp home" option. Mind you I had a 66kW Isuzu under the bonet.

Can I recommend replacing the gears in the transfer case to get your higher road speed ratios?

Cheers
Ben

 

[Jayce]

Looking at the installation guide over the weekend, I noticed that my linkage setup is not quite the same as in the manual. Could I ask someone to measure up the length of the linkage rod , the one that looks like a big tent peg with two holes in it. The second thing I need measured up is the L-shaped bracket, mine has only 3 holes where the manual shows 4. I want to know before hand what changes need to be made before I go and cut holes all over my transmission housing. :confused

The other thing which I have noticed, more obviously becuase I dont have a gearlever for my unit, is that instead of the gearlever screwing in, I have a bolt through setup similar to how the linkage rod fits to the pivot unit.


Thanks

Jayce

 

[Gripper]

OD third to direct top can be achieved by hooking your index finger around the gear lever when holding the OD lever against the palm with fingers three and four. De-clutch, gently pull back and unleash those rampant horses once again. Bloody hurts if it kicks back though :complain:

"Whines like kids"

 

[bhodisatva]

I've used my overdrive as a splitter gear throughout both low range and high range 1st thru 4th with no problems whatsoever. Essential when towing up hills and 2nd is too low and 3rd too high, just nice to have that extra gear to bring the revs down. Have heard many a horror story and fairy tale concerning the the use of the overdrive unit between 1st and second but from daily experience all i can say is it's never done my O/D, gearbox or engine any harm whatsoever.

 

[ally.m]

re over drive

well thank u all i am getting an over drive for my ser 2a and now i am totally confused u have done the world a great servise thank u all happy motoring i think i will walk home
:clap: :beer:

 

[bbuzz]

Hi,
I saw your post re the Fairey Overdrive and have an enquiry. I have a Fairey in a 1984 Landcruiser but I need bearing sets. I am having trouble getting all of them in Australia. Do you know if there is a supplier in South Africa I could contact?
Cheers
Bill

 

[danzel]

Superwinch

hello mate got mine.. superwinch ,from a dealer that offered a great deal on almost all parts, with the superwinch, it can competently pull a vehicle out of a drain even when having the harshest weather condition. i am completely sure of the capability of the winch to handle heavy-duty activities because this are made to be superior in terms of quality.

 

[pickuprover]

hello mate got mine.. superwinch ,from a dealer that offered a great deal on almost all parts, with the superwinch, it can competently pull a vehicle out of a drain even when having the harshest weather condition. i am completely sure of the capability of the winch to handle heavy-duty activities because this are made to be superior in terms of quality.

I think that the original poster was talking about his Overdrive, not his winch... but glad to see you here and glad you like your winch.. welcome.... :wave:

 

[BDAjames]

hi evryone, im james, 17. i just bought a 1982 series III. im planing to buy a fairey overdrive unit and was just wondering how long it would take and what tools i would need to install it? also, i know O/D's are intended to help fuel consumption, but do they add anything to the top speed?

help much appreciated

james

 

[archaeology_student]

Fairey O/D is not bad, but from reading posts around the net the Roverdrive from RockyMountain Parabolic. Take a lookey see

 

[pickuprover]

One advantage of the Roverdrive (other than it does not howl like a banshie when engaged.. ) is that parts are readily available for them (they are being manufactured as we speak.). One thing I worry about with the fairey, there is not a Rover Forum around that does not have a "I need parts for my Fairey overdrive..." posting on it, and after reading the responses..... yep I am planning on a Roverdrive when I do the switch...

 

[BDAjames]

hi
thanks for the advice. i looked up on the rockymountain OD's and the're definately the better unit. however im a little short on cash right now and evrything in the UK is overpriced! so im gonna go for the fairey (£50-£200 on ebay.co.uk). i know it will need maintinance more than ofter but the parts are easily availible and very cheap.

james