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Post by felixlighter on Aug 18, 2012 19:53:19 GMT
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Post by redsunbeam on Aug 25, 2012 8:23:21 GMT
Steve, pm sent
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Post by felixlighter on Aug 25, 2012 13:37:32 GMT
redsunbeam , PM sent
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Post by bissmire on Oct 1, 2012 13:51:13 GMT
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Post by johnwp5bcoupe on Oct 1, 2012 16:07:03 GMT
If you are running a standard 3.5 the ratio will be too high on roads with inclines or restricted speeds like 30 to 50mph plus the oil will be running hotter as the torque convertor will be working overtime if you are doing 70 mph on the motorway all day fair enough or running a bigger lump! even then it concernes me how this diff change will affect the BW35 gearbox reliability particularly a high mileage one l
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Post by Welsh Warlock on Oct 1, 2012 16:27:16 GMT
So, as I'm running a 3.9 with a rebuilt gearbox (albeit s few thousand miles ago (eh Harvey?) and am planning on putting in a transmission oil cooler separate from the gearbox and my diff is slack (ooer missus) is this one for me?
Looks expensive though.
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Post by harvey on Oct 1, 2012 16:34:52 GMT
I'm not sure my memory stretches that far back.... ;D
Personally, I'd advise against it.
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Post by enigmas on Oct 1, 2012 23:27:19 GMT
In relation to gearing ( a combination of tyre diameter and diff ratio) ideally you should try and match the optimum cruising speed with the engine's 'torque' peak. In this way you maximise both fuel economy and have the engine running at it's most efficient rpm range.
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Post by Steve P5b on Jan 1, 2015 18:57:47 GMT
Just had a result of tests of a p5b with 2.8:1 ratio diff and 5 speed manual gearbox modifications returning the equivalent of 46 Miles Per Gallon running on LPG at motorway speeds. Sounds amazing , but true. Well done Gerry :)Hopefully on show at this years P5 National event.
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Post by enigmas on Jan 2, 2015 4:27:45 GMT
Steve et al, although the intention is laudible, I still don't believe it's the way to go (especially wih a 3 speed auto) not unless you've got some serious cubic inches (4.6 - 5 litres) otherwise you'll be driving with more throttle opening generally (for no fuel efficiency benefit) and outside the engine's torque peak. It will also accelerate like a slug. The gearing jump is just too high...perhaps a 3.3 or something in that range would be more suitable overall. It would be a lot easier to look for a complete BW diff (drum to drum or disc to disc) of similar width and fit that. BW diffs have a vast range of ratios available. Aussie Ford 6s and V8s from the 60s to the late 80s all have suitable diffs and ran BW35/40/51 autos, all 3 speed. There's even an Aussie club member who's done this with a complete disc to disc unit on his P5B sedan but he runs a P76 4.4 engine. Twenty years ago I had the BW center gear section welded between the Rover axle tubes retaining the P5 axles and drum brakes (now discs) by a diff specialist. Yes it was expensive ($2500 AUD). So I thought about this conversion long and hard. It only made sense to me because the car is a keeper. The car cruises easily at it's torque peak of 2500 rpm (P76 4.4 litre engine) at well above legal road speeds and I rarily if ever need to rev it over 3000 rpm. With a 3.5 engine and a 2.8:1 ratio diff forget about towing anything as the car will really struggle. There is no easy, cheap option and if you don't like the conversion it could turn to tears. John's Laycock overdrive solution is a well thought out mod that improves the car in all respects. Fitting a Rover ZF 4 speed auto also makes sense. www.aussiev8.com.au/driveline-suspension/33590-diff-information-thread-basics-salisbury-borgwarner-bw78-ford-9-a.html
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kaiser
Rover Fanatic
worth his V8 in gold!
Posts: 136
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Post by kaiser on Jan 2, 2015 7:37:27 GMT
Just had a result of tests of a p5b with 2.8:1 ratio diff and 5 speed manual gearbox modifications returning the equivalent of 46 Miles Per Gallon running on LPG at motorway speeds. Sounds amazing , but true. Well done Gerry :)Hopefully on show at this years P5 National event. Claims such as this one is interesting, but largely irrelevant. The claimed consumption figure of about 16km per liter (or about 6 per hundred) is so low as to be suspect in itself. The added bit of information about LPG should make people think, because the calorific value for gas is lower than for petrol, and the consumption in liters will be higher. It then states the equivalent consumption is 46 miles per Gallon. I assume imperial. All in all, nothing is said about the measurement and/or possible assumptions in converting from gas to petrol, and I find it highly doubtful that any consumption figures close to this can be achieved, unless you find a very looooong hill, somewhere. As for my car, it uses about twice as much as claimed here, and I think that would be close to what can normally be expected. Overdrive and freewheel in the Rovers of yore each are credited with about 10% saving, but I don't think much more can be achieved by changing the gearing, and it certainly is not a one way street, that the higher the gearing the lower the consumption, ad infinitum.
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Post by johnwp5bcoupe on Jan 2, 2015 9:03:53 GMT
Promoting this as a good conversion for all 3.5 users would be ill founded, as per previous posts I can replicate the diff ratio and I KNOW there are road conditions where the standard 3.5 will struggle unless you manually change down and my 3.5 is no slouch. I understand the car in question is a 5 speed gear box so in fact no relationship to the majority of guys reading the fantastic results 46mpg which on petrol may be 23-28mpg at motorway speeds? up and down hills? round town use? So IMHO this conversion is not the panacea for all 3.5 owners, read previous posts on the strains etc on the BW35 gearbox! What worries me and others like Vince and Harvey is a conversion which doesn't take in all the aspects of road conditions and the load on the transmission train
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