I've seen a few ads on eBay for these, and I'm thinking of getting one as I keep looking for fifth in the 'box. Some questions:
What's a fair price? (I know, about the length of a piece of string :) )
What extra economy would I get from it, roughly? With new tyres, I'm getting about 15.5 mpg at the minute.
Some of the units have no lever, are these difficult to obtain/ fabricate? My 110 is LHD, does it make life more difficult? Is it an up-and-down lever (like the tranfer box) or an in-and-out knob (like the diff lock)
If it's the Fairy Overdrive it's an up/down or forward/back like the transfer box lever. I only ever saw fuel consumption figures for the early RR and it was a claimed 10-15% improvement. I'm not sure that it is really that achievable though.
As for cost - not my area of knowledge. It's not tricky to fit, but would be an interesting project. Does anyone know whether parts are still available for these units?
Don't consider it if an economy improvement is your only justification.
It's rather like the official figures - very dependant on carefully controlled steady state conditions which don't relate to the real world. You'll just go faster!
There may be a decrease in noise for the same ground speed which you may welcome.
I did have one on mine and it did make for more restful long journeys but there was no improvement in fuel consumption with my driving style. I would fit one again.
OI got a nice one, off the box, for 90 quid a month back, but I'm not sure what else I need to install it - it came with the big lump, and a single pinion. Any ideas what else I need ?
I've had one fitted to my '75 RR about 25 years ago and I can't say that I've ever had a mileage improvement, mainly decreased noise and definitely improved temperatures for water and oil. This is in Australian temperatures of 30 to 45 degC though. I found that the 25% overdrive seems to be excessive and would have preferred about 15% as on even smallish hills the speed will drop off considerably. I think that it needs a more powerful engine to get the best use of it, but then again mine is getting on a bit and could do with its first rebuild.
I was told at the time of install that the fitting of the OD had one benefit of removing a potential major transfer case failure because it replaced a couple of gears/bearings that could become dislodged and destroy the box. Don't know if it was true, but sounded good at the time.
The one downside of an OD like this over a 5 speed is that you can forget that you are in OD when passing or stopping. Acceleration and engine braking are diminished.
The only web site that I found about the units seems to be still working and they may still have parts available.
Got one on my 3.5 ser 1, agree with previous posts, goes faster (fear level goes up )noise goes down and long journeys can at least be contemplated but not much fuel benefit but maybe thts down to me going faster. Wouldnt be without it ! Nick
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