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Post by norvin on Jan 31, 2010 10:36:20 GMT
Is it worth the trouble of trying to fit another type of box? as the BW35 does seem to match the V8 engine very well.
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Post by Phil Nottingham on Jan 31, 2010 11:26:06 GMT
It was only just up to what is now considered a low power output of the standard P5B V8 although it can be uprated a little it will not last long with hard driving of even the standard V8 never mind any tuning and/or overboring
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Post by redsunbeam on Feb 16, 2010 16:32:22 GMT
Did anyone manage to get the dimensions of the gearbox?
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Post by Deleted on May 28, 2010 10:25:48 GMT
I can give some thoughts on this having owned a P6 3500 with the '35, and currently an SD1 with a GM TH180.
Basically, the '35 as installed is a bit of a dog. It's really not up to the torque - that's why you can't access first gear above about 25 mph, when the car can do about 50 in 1st. There's also no part throttle change down. The setting of the control cable is critical for correct operation and best life - if the line pressure is too low you'll get smooth changes but clutch slippage and short life. If too high, rough changes. So first make sure the accelerator pedal of opening the carbs fully before attempting any adjustments, as the two are related. Just about every P6 I've driven has had the control cable adjusted to get the kickdown to work - when it was the throttle linkage that was worn. This messes up the gearchange speeds and quality of them. The P5B might be better in this respect, though.
The 65 as fitted to early SD1s is a much better, stronger box.
The TH180 is a much more sophisticated box with vacuum control and a separate kickdown cable. This gives a very smooth changing box which also has good part throttle kickdown. It will also kickdown into first into near the maximum speed for that gear. But it's not quite so long lived as the '65.
As regards 4 speed units, the obvious one is the 4HP22 - as it is the only 4 speed to have been mated to the RV8 by the factory. But this was engineered for the Range Rover, so the gearbox is spaced off the engine by more than is needed to fit between the engine and transfer box - the actual box is shorter than the manual. this is achieved by a deeper bellhousing and spacing the torque converter off the drive plate. Which gives bulkhead clearance issues on the SD1. Dunno about the P5. The Sherpa box uses the same arrangement - space obviously not being an issue with that. They can be difficult to find - mainly used in ambulances and some police vehicles, so not in every breaker's yard. The RR unit can be modified by fitting the tail from a RWD unit from a BMW etc. But you'd need some experience of working on autos. Early ones are cable controlled - later ones electronic. The Aisin Warner is a good box and is small enough to fit without body mods - but needs an adaptor ring between bellhousing and engine. Or some serious welding.
The TH180 has a removable bellhousing, and some say a later GM 4 speed can be mated quite easily to that - but they aren't common in the UK. They are also electronic control - but aftermarket ECUs for stand alone use can be bought quite cheaply from the USA.
I've got both an Aisin Warner and a 4HP22 (RR) here but have decided against both. As my other car is a BMW with a 5HP18, and that is a superb box, so I've decided if major engineering is needed I might as well go the whole hog. it is electronic control, but an aftermarket ECU is also available. It has a torque converter lockup clutch, so gives the same or better fuel consumption as a manual on the open road.
hoipe thos gives food for though. ;-)
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Post by harvey on May 28, 2010 10:55:54 GMT
Basically, the '35 as installed is a bit of a dog. It's really not up to the torque - that's why you can't access first gear above about 25 mph, when the car can do about 50 in 1st. Depends on the specification of the 35 box in question. On a Rover you should be able to select FIRST at 100mph if you really want to.....
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Post by Deleted on May 28, 2010 11:19:03 GMT
Basically, the '35 as installed is a bit of a dog. It's really not up to the torque - that's why you can't access first gear above about 25 mph, when the car can do about 50 in 1st. Depends on the specification of the 35 box in question. On a Rover you should be able to select FIRST at 100mph if you really want to..... Oh indeed. However, this was inhibited on the two P6 autos I owned - and the P5B coupé belonging to a friend. Are you saying some P5Bs would allow selection - or kickdown - to 1st at above about 25 mph? BTW, sorry for some of the speeling mistookes on the earlier post - was done on my phone while waiting for an appointment. ;-)
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Post by harvey on May 28, 2010 12:30:40 GMT
Depends on the specification of the 35 box in question. On a Rover you should be able to select FIRST at 100mph if you really want to..... Oh indeed. However, this was inhibited on the two P6 autos I owned - and the P5B coupé belonging to a friend. Are you saying some P5Bs would allow selection - or kickdown - to 1st at above about 25 mph? I never said anything about using the kickdown. I doubt that it was inhibited in any way at all, you just didn't know how to do it....... Rover 35 (and 65's) do exactly what they say on the selector.
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Post by Deleted on May 28, 2010 16:24:45 GMT
Oh indeed. However, this was inhibited on the two P6 autos I owned - and the P5B coupé belonging to a friend. Are you saying some P5Bs would allow selection - or kickdown - to 1st at above about 25 mph? I never said anything about using the kickdown. I doubt that it was inhibited in any way at all, you just didn't know how to do it....... Rover 35 (and 65's) do exactly what they say on the selector. Let me get this clear - you are saying that all B-W model 35 as fitted to Rover V-8s in the early days could select 1st gear at any speed?
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Post by harvey on May 28, 2010 17:38:14 GMT
I shouldn't have been so flippant earlier, because I've steered you in the wrong direction slightly though a bad turn of phrase, but in effect what i said is true, with the PRND21 selector pattern, 1 & 2 give you exactly that, pull away in 1 and it will stay there regardless of roadspeed, regardless of how much the engine revs, up to whatever speed it would get to before the engine blows up, the same thing applies to 2, it will pull away in second and not change from that gear. This is unique to the boxes fitted to Rovers, as all others shunt 1-2 2-1 in the "2" position. Normal downshift roadspeeds in fully auto can be increased by manual shifting, and those manual shift speeds can be further increased by operating the box and driving the car in a particular manner, but, as in the case of stall tests, which if not carried out in a safe manner by someone who knows exactly what they're doing can be a bit dangerous, so can messing about trying to make a box do something that it really doesnt want to do, and for that reason I'll keep it to myself, but rest assured that you can get it to downshift into first at speeds above 25mph, but it will always be at a slightly lower speed than the maximum kickdown upchange would be. You should be able to get at least another 10 mph above the 25 that you mention. I can't remember offhand whether selecting "2" at speeds above the maximum 2-3 kickdown upshift speed causes an immediate engagement of second, but as I said earlier, trying to do so could be nasty, and I won't be trying any time soon. I will however recheck the course notes as I'm sure there's something in there. What you say about the linkage problems is relevant though, and has been well documented on here previously, as is the fact that the 35 box is working at its limit behind the Rover v8
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Post by Deleted on May 29, 2010 8:06:17 GMT
You've not steered me in the wrong direction since at one time I knew these boxes inside out having repaired and overhauled several, but no longer have a vehicle with one. It's more worrying that you may have misled others still using this box, though. My original comment was:-
And I stand by it as being accurate.
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Post by Deleted on May 29, 2010 8:19:55 GMT
the same thing applies to 2, it will pull away in second and not change from that gear. This is unique to the boxes fitted to Rovers, as all others shunt 1-2 2-1 in the "2" position. No it's not. Certain other B-W boxes would start and stay in second if the intermediate hold switch was made. I had a Jaguar like that. And very likely others I don't know about. The second gear start could be useful for lazy drivers as in this mode the one way clutch prevented roll back on a hill. When moving off on a steep hill you apply throttle then flick the lever back to drive, where the box will then change to 1st and drive off normally.
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Post by enigmas on May 29, 2010 8:53:45 GMT
These threads always amuse me. Both the BW40 & BW51 (OZ boxes) have a part throttle shift into 1st gear. The BW40 internals will fit into an English BW35 case (my P5 MK3 4.4 litre hybrid runs this set up in the original casing) Aussie Fords of the 70's (4.1 litre) ran a GTS selector pattern, i.e. 1st stays in first, second stays in second...no matter what you do with the throttle... drive it like a manual minus the clutch. The BW40 & BW51 are beefier than a BW65 which runs the same internals as the BW35 but with repositioned front and rear servos hence the narrow case and narrower trans tunnel. They also have significantly wider (flex) bands. The reason it won't access 1st gear beyond a certain point is that it would lock up the rear wheels. The manufacturer didn't really want this to occur. If hand brake style turns is what you want to do...there are ways to alter the throttle body. It can be fully manualized up and down the range. The P76 probably ran the highest internal pressures with a PRV of 3" in length. The BW51 valve body will fit BW35 & 40 transmission cases but not the gear assemblies. The throttle valve cam is adjustable (can be moved back and forth) on its seating on the valve body as well, but there is a recommended setting. The kick down cable is then a secondary fine adjustment. There are 3 throttle valve cams available with the BW51 producing the best part throttle changes. These were developed into the 1980s. ...But if you want something different take a look at this. www.leylandp76.com/technical/tech-th700v8.html
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Post by Phil Nottingham on May 29, 2010 9:32:09 GMT
It has always been accepted from new that the BW35 was at its limit when installed behind the P5B V8 and if not looked after or regularly driven hard then it failed early.
The 1st P5B's were designed as 2 speed starts with the D1/D2 shift as even Rover thought it not smooth enough for chauffuer driven cars and the more sedate drivers who bought them especially saloons. The later D-2-1 was specified for Rover however is more flexible and suitable for faster drivers and better than the standard shift for 2 which gives only 1st speed start and holds 2nd till speed drops and prevents top speed engagement completely and offered by other cars makes like Rootes.
Even now as then most P5B drivers just stick it D and never bother unless problems arise
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Post by Deleted on May 29, 2010 10:57:53 GMT
These threads always amuse me. Absolutely - always full of misinformation. ;-) The car maker can specify how they want the box controlled I'm sure anything can be done - but at least one factory upgrade to the '35 meant some machining work to the case if you wished to fit the later drivetrain. I'm afraid that's not the full story. You are restricted to about 25 MPH as a max to change down into 1st to avoid excess wear/damage to the box. Straight from the horse's mouth on the B-W service/overhaul course I went on. Plenty other vehicles allow you to get 1st gear at speeds well above that by using kickdown, or manual selection. If in the UK, the easier way might be to fit a GM TH180 as used on later SD1s. It performs faultlessly as standard with no need for mods, and can be bought cheaply. Only possible gotcha would be the speedo drive.
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Post by enigmas on May 29, 2010 11:36:34 GMT
Well, whatever makes you happy...but the BW40 internals fit straight into a BW35 English case...no machining...Try it next time you rebuild a unit. Upgraded P76 BW35 (Go to middle of page) www.leylandp76.com/private/vic/motivator.html
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Post by Deleted on May 29, 2010 13:19:02 GMT
Well, whatever makes you happy...but the BW40 internals fit straight into a BW35 English case...no machining...Try it next time you rebuild a unit. Upgraded P76 BW35 (Go to middle of page) www.leylandp76.com/private/vic/motivator.htmlI'm not sure if it was ever fitted to a UK car - and importing such a thing or buying all new parts could be costly.
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Post by harvey on May 29, 2010 19:06:19 GMT
the same thing applies to 2, it will pull away in second and not change from that gear. This is unique to the boxes fitted to Rovers, as all others shunt 1-2 2-1 in the "2" position. No it's not. Certain other B-W boxes would start and stay in second if the intermediate hold switch was made. I had a Jaguar like that. . Other BW boxes may well do that when they have an intermediate hold switch, but I can't think of any BW35's that ever had one, that IIRC was only on the DG boxes, which were used on the 3 Litres, and some Jaguars as you say. The only other 35 boxes that will start and pull away in second are the PRND2D1L boxes when D2 is selected, but they will change into Top as roadspeed increases. When this selector pattern was deleted in favour of PRND21 Rover were the only manufacturer that retained the Second gear pull away.
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Post by harvey on May 29, 2010 19:11:27 GMT
You've not steered me in the wrong direction since at one time I knew these boxes inside out having repaired and overhauled several, but no longer have a vehicle with one. It's more worrying that you may have misled others still using this box, though. My original comment was:- And I stand by it as being accurate. Well in that case I won't say anything further to try to change your mind, but should you care to read the book, you will see in there how to get the box to change into first at a road speed greater than the maximum that the kickdown or manual selection alone will allow.
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Post by harvey on May 29, 2010 19:34:51 GMT
I'm sure anything can be done - but at least one factory upgrade to the '35 meant some machining work to the case if you wished to fit the later drivetrain. Perhaps you'd care to enlighten us about this particular upgrade.
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Post by johnwp5bcoupe on May 30, 2010 5:50:47 GMT
I'm sure anything can be done - but at least one factory upgrade to the '35 meant some machining work to the case if you wished to fit the later drivetrain. Perhaps you'd care to enlighten us about this particular upgrade. All those years you spent rebuilding BW35's etc Harvey how come you missed that factory mod
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Post by Deleted on May 30, 2010 8:00:59 GMT
Perhaps you'd care to enlighten us about this particular upgrade. All those years you spent rebuilding BW35's etc Harvey how come you missed that factory mod Given what Harvey said earlier:- " On a Rover you should be able to select FIRST at 100mph if you really want to..... " not really surprising.
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Post by harvey on May 30, 2010 9:23:55 GMT
Perhaps you'd care to enlighten us about this particular upgrade. All those years you spent rebuilding BW35's etc Harvey how come you missed that factory mod Asleep that day, obviously.........
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Post by Deleted on Jun 22, 2010 22:22:05 GMT
Sorry am I missing some thing again,, (It has always been accepted from new that the BW35 was at its limit when installed behind the P5B V8 and if not looked after or regularly driven hard then it failed early.) Regularly driven hard then it failed early....! If its week how can driving it hard help..? I have a hard time keeping my self from hiting the kick down every day.. I have been beating my self up every time I let the old girl pick her skirt up and make a dash for it.. By the way you guys loose drive out of a corner if she sways over to much..? feels like the clutch is in..! Guilty
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Post by Phil Nottingham on Jul 2, 2010 12:08:54 GMT
No! - if it IS regularly driven hard it WILL fail early - gently does it
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Post by enigmas on Jul 2, 2010 12:42:59 GMT
Kanter, the ATF fluid level in your gearbox is probably incorrect and the 'pickup' is probably drawing in air as you round a corner 'hard'.
I still run the rear pump in my P5 Mk3 (V8) hybrid and if the fluid level is incorrect and I am descending a long steep section of road...the rear pump can draw in air and cause some unusual symptoms until the car levels out again.
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