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Rover V8, Discovery diffs, AND overdrive??


Scooby Jim

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Tbh guys don't worry too much about off-road, as the chances of it seeing anything technical is going to be negligible.

Having never driven the Landy I'm sure its just something I will have to get use to, with the diffs. And the Over Drive I can fit it, and if I want I can either remove, or only use occasionally. OR I can always fit series diffs. I will probably get a set and see what they are like, and if I am planning to go properly off road I can plan in advance and change the diffs. This is not going to be used a lot, as I have 2 other cars, so mainly cruising around, or driving in the snow. Daily drive it is not.

Braking wise I have changed from the standard 10 inch single line system (non servo), to 11x3 twin leading shoe fronts and 11x2 single leading shoe rears now twn line and servo assisted. So I'm well over specced in that department.

Hmmm can see me having to change gear a lot to make sure the engine doesn't try and rip the box to bits, but driving vehicles with 12 manual gears it should be ok lol.

Only way i could see the tyres helping is if I went to small wheels, which isn't going to happen as it would look bloody stupid. Just means that I am slightly more limited in getting larger tyres, but as I don't want to go bigger than they are standard just wider I should be ok.

As for holding speed going up a hill, I can only imagine that the V8 will have the torque, but if needed I could always change down and add OD?? Same as dropping 2 on the truck and adding a half gear (1 back up) if that makes any sense??

Why didn't I just fit series diffs?? lol.

with the fairey overdrive it is advisable to only use in third and 4th, i was always worried about its strength, however the 3rd and 4th was specced behind a 2.25 to avoid breaking so you would think a TDi would munch it, i have accidentally forgot to take it out before and set off like hell in 1st overdrive and its always handled it. i dont make a habit of that though. i do use it in lower gears around town with a feather foot too just for convenience of that half gear.

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I found it very useful having the overdrive with defender diffs ( behind a 19J engine ) in my lwb ser 3 safari. It pulled acceptably from about 50 with overdrive in 4th ( series 3 box ). On a motorway run at around 60mph I would get about 45 mpg, dropping to about 40mpg if I was towing the caravan. As Josh suggests, you need to put it in and out of O/D a fair bit, but I was expecting this, so no problem. I have never driven a V8, but as it has more oomph than the 19J I would not expect any problem, unless you do a lot of offroad work and need the lower gearing.

O/D is off mine ATM for a rebuild, and it is quieter without it.

HTH

Sorry, but I have a hard time believing claims of 45mpg from this type of Landy, no matter what the engine, let alone 40mpg towing.

Lets face, a Freelander 1 with a modern BMW TD4 doesn't get anywhere near this, despite similar or less weight, far superior aerodynamics and vastly less drivetrain resistance.

So an old 19J in a 109 :hysterical:

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Depends. For casual trundling along a field or greenlaning I suspect they are fine. For more technical and challenging off roading, then I think you'd find the crawl speed too high in low 1st.

I have only ever found it a little too high geared once, i was in the woods at bala in a particularly technical spot. although i managed to cope fine

Sorry, but I have a hard time believing claims of 45mpg from this type of Landy, no matter what the engine, let alone 40mpg towing.

Lets face, a Freelander 1 with a modern BMW TD4 doesn't get anywhere near this, despite similar or less weight, far superior aerodynamics and vastly less drivetrain resistance.

So an old 19J in a 109 :hysterical:

considering my geared up 200TDi gets 35mpg i also find this hard to believe ( i thought 35 was bloomin good for what it is to be honest) hoewver by a freak miracle i did manage about 39mpg once. havent managed it since mind.

on the plus side it doesent drop much when towing :)

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I have only ever found it a little too high geared once, i was in the woods at bala in a particularly technical spot. although i managed to cope fine

Likewise here, although the 3.9 does have a bit more low-end grunt than the 3.5. It was only steep descents that made me think twice, and I'm sure most people would live with it. On the motorway it still needed a higher gear even with the OD!

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20 years ago my favourite Series 3 SWB I ran exactly that setup. Standard gearbox with overdrive, No mileage 3.5 EFI. (I still have the engine) Standard Series radiator with electric fan. Milner conversions oil filter housing and conversion ring. Stage one front axle with the big brakes and free wheeling hubs, 3.54 diffs, and BFG 750-16 Trac edge tyres.

Worked a treat with no problems at all except it kept breaking rear halfshafts at the diff end. Could also tow a loaded car transporter trailer with no problems either.

Could also do 20 mpg if wanted, and 24 mpg if I tried really hard. Or 8 mpg if I used the performance.

Worked well on the road in all conditions as far as I remember with no drawbacks apart from the whining gearbox/overdrive

A bit high geared off road in high , but then thats what low box is for !

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I've had my S1 V8 on 3.54 diffs for thirty years and not bothered about changing tbh. Off road I have driven a log bridge at tick over and other obstacles without issue but S1 has the lowest transfer box. Handbrake is an issue on steep hills so now have an X-Brake.

On road it cruises at 80without issue only driven flat out once to catch and overtake a 110. Speedo is 33% out so converting to digital soon the kph idea is interesting but I also want to turn it off when on private land due to insurance limited mileage!

Acceleration wise it would beat a hatchback up to 2.0l from the lights but that was some years ago and cars are much faster now. Even on 7.50 16 tyres it will drift quite well.

Yes I am a hooligan!

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I've only had my Stage One V8 for around 7 years but have changed the gearing. I changed the high ratio transfer gears for Range Rover ones (there are various ratios available and I can't remember, off the top of my head, which I have! I retained the standard low ratios, best of both worlds). I also moved to 255/85 tyres and retained the standard 3.54 diffs. All up, that's about 25% over-geared in top. With a tired, standard motor, it worked but was sluggish. I now have a good 3.9 and the gearing is absolutely perfect. The vehicle is very willing, even with a trailer, and still able to take decent hills in top etc. The SD1 V8 will be similarly capable of handling greatly raised gearing, I'm sure.

Note, though, that the SIII gearbox wasn't designed for that much torque and I'd want to drive it very sympathetically, if I was you. The LT95 in the Stage One is very sturdy, by comparison.

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I have only ever found it a little too high geared once, i was in the woods at bala in a particularly technical spot. although i managed to cope fine

I think it depends what sort of off roading you do. If you are into trials, then even with stock gearing it can be a little too fast for some technical sections.

Likewise if you are on rocks or very challenging terrain. I suspect it's not a major issue, and some people like to drive faster off road than others. But I think it's worth mentioning.

considering my geared up 200TDi gets 35mpg i also find this hard to believe ( i thought 35 was bloomin good for what it is to be honest) hoewver by a freak miracle i did manage about 39mpg once. havent managed it since mind.

on the plus side it doesent drop much when towing :)

I suspect that in most cases it's down to people miscalculating and also by only using the vehicles tacho for the travelled distance.

I've been around Land Rover's all my life and between myself and close family I think we've had somewhere in the region of 40-50 of them. Of all shapes and sizes, and no matter how any where driven, I've not seen close this kind of mpg from them.

I'm not sure I can really believe 39mpg either, unless it was fill up, drive 10 miles at a constant 50mph and refill and work out the mpg, despite not even using a gallon. The margin of error is simply huge.

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I think it depends what sort of off roading you do. If you are into trials, then even with stock gearing it can be a little too fast for some technical sections.

Likewise if you are on rocks or very challenging terrain. I suspect it's not a major issue, and some people like to drive faster off road than others. But I think it's worth mentioning.

I suspect that in most cases it's down to people miscalculating and also by only using the vehicles tacho for the travelled distance.

I've been around Land Rover's all my life and between myself and close family I think we've had somewhere in the region of 40-50 of them. Of all shapes and sizes, and no matter how any where driven, I've not seen close this kind of mpg from them.

I'm not sure I can really believe 39mpg either, unless it was fill up, drive 10 miles at a constant 50mph and refill and work out the mpg, despite not even using a gallon. The margin of error is simply huge.

I like to use both technical and faster techniques off road. when the situation suits of course. :)

and it was over a full tank of diesel on motorway driving. i suspect i wont be seeing those figures again for a while because i had temporarily de-tuned the pump a tad. (not too much though)

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Some very interesting comments here, from those who have had the setup looks like its a good setup. I at the moment am not planning on doing a lot off road, most will be driven in the summer roof off and cruising with a V8 soundtrack, so think I should be ok. If not I can always change the diffs again lol.

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I knocked up this spread sheet, hope it helps a bit. Of course running bigger or smaller tyres will affect this.

Overall I think it depends on what you want to use it for. If you see lots of motorway or high speed cruising, where every mpg counts. Then taller gearing makes more sense.

The flip side is, taller gearing also dulls performance and makes a vehicle feel less lively. A stock 3.5 on SU's/Strombergs is not a revvy engine and over gearing them can make them feel more sluggish than they ought to be.

Personally I've driven/owned under and over geared V8's. And I much prefer something more lively, you also won't need to change gear as much. On this note, looking at the tables I'd personally prefer the 4.7 diffs in a vehicle such as this, I think it'd just make it more fun. The reality is, they are noisy, bumpy, usually have wobbly steering and drum brakes. So cruising above 60mph is far less likely or important.

SeriesGearing47diffs.png

SeriesGearing354diffs.png

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Just going back to the fuel economy thing (which was way off topic!), I recall reading in LRO years ago, when the first TDi Range Rover came out, that someone did a Land's End to John O'Groats run in one and got 52 m.p.g., setting a record in the process. Good economy is possible...

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Saved that spreadsheet, will probably fit the Overdrive as I already have the diffs fitted, I will probably get a set of series diffs as mine that came out are munched.
Didnt look to me like a standard series diff though, but can't be used as the crown and pinions gears are chipped and munched.

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This is my type of pie chart.

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Just going back to the fuel economy thing (which was way off topic!), I recall reading in LRO years ago, when the first TDi Range Rover came out, that someone did a Land's End to John O'Groats run in one and got 52 m.p.g., setting a record in the process. Good economy is possible...

Must have been on the back of a trailer..... ;)

Seriously, I'd love to see someone actually get these kinds of mpg. But I just don't believe it.

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Must have been on the back of a trailer..... ;)

Seriously, I'd love to see someone actually get these kinds of mpg. But I just don't believe it.

I'm pretty sure it's a certified record. Shouldn't be too hard to check.

Really, though, I don't understand people who get negative about others' achievements just because they don't match their own experience. In terms of fuel economy, I'm almost the other way. When someone says he/she only gets 25m.p.g. out of a diesel Land Rover, I immediately think "what on earth are you doing so badly to get that"!

Interestingly, my first Land Rover, back in the day, was a humble diesel Series III (and, oh, how little power that had!). I used to get a reliable 35 m.p.g. (no round town driving, all open road) simply by putting my foot hard down and letting the governor hold it at maximum revs (52m.p.h. on the speedo). I then put an overdrive on it and, no matter how I drove it, I couldn't get better than 30 m.p.g.. It was easier on the ears, though!

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The thing is, when you get claims way above what the makers claim, it just sounds fishy. And it's so easy to balls up the calculations. Or simply start with inaccurate data.

For instance, I had a mate who used to work out his mpg. But he'd do it by driving from half tank on the gauge to quarter tank and claim that was 'x' gallons. Despite having no idea how much fuel was really being used between those two points. Even reading the gauge is not going to be accurate. But he used to swear by his claims, as I'm sure others do, even if they are just as misguided.

As an example, if you have a speedo drive setup for 7.50's and you are running 205's. Then your odometer will not be accurate. Could be 10% out easily, as they probably aren't accurate at the best of times.

You do an indicated 100 miles. You then fill up at a different petrol station and you put what you think is a similar amount of fuel in. But being as you can't see into the tank, it's quite hard. Lets say you put in 2.86 gallons.

This means

100 miles / 2.86 gallons = 34.96mpg

However the reality might be you only covered 90 miles and you actually put in half a gallon more fuel.

90 / 3.36 = 26.79mpg

I'm in no way saying you did this. But you can see how some fairly simple, easy and mundane errors can drastically change the end claims.

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