Choices for new auto gear box P6B

ghce

ghce

Well-Known Member
I have for a long time wanted to change my 65 box to something else, something that doesnt say "the car is moving lets go straight to 3rd gear" but what choices are out there?
A few years ago I considered the ZF 6 speed box as is fitted to the BMW735i cars, worked out the ratios and rpm values as compared to the HP and weight when compared to the 735i and that looked like a real winner with side advantages of a lot less box weight and improved box efficiency(better fuel economy).
The big problem would be marrying the box to the engine and then setting up the electronic control :? it all stsrted to seem a little to hard.

What other boxes have people used and what are their relative advantages? really doesnt seem to be any point in getting under 5 speed and an overdrive gear would be a must have as the P6B's rev far to high at any thing above city driving speeds.

Graeme
 
This summers project is fitting a ZF HP22 gearbox to my P6b, this early ZF box has no fancy electronics so makes the easiest of conversions.

These gear boxes are fitted to numerous cars - BMW 3 & 5 seies, Puegeot, Jag XJ6 40, Discos, Range Rover, LDV police & Ambulance in the late 80's early 90's. Its quite popular in the Stag club and their web site has some useful info.

In practice you need a box from a Jag and another from a Range Rover, use the fly wheel, torque converter & bell housing from the RR and the box & tail shaft from the Jag or other donor.

Unless you get an LDV box which also has the speedo output, you will also need to convert the speedo to an electronic one, there are a couple of companies that provide speedos and magnets/sensors for the prop shaft.

The key benefit of this is a cruising speed of 90mph at a little over 2700 rpm.
 
That's some benefit. A long-term member of the P5 club has installed one of these boxes into his P5B coupe mated to a 4.9 engine IIRC.
 
The HP22 was also fitted to Maserati Biturbos ... so it presumably takes quite a bit of load. My OTHER car is a BMW 325TDSA, a diesel with a 5HP18 that has a 4+2 overdrive setup (+ Sport and Winter settings) - at 200 kph on the Autobahn we nudged 3000 rpm, relative to keanej's comment on cruising characteristics. I know little of the electronics that apply to this box, or about fitment issues on a P6.

The action is smooth, quick, beautifully load-sensitive and the box does everything it should. Was never really an auto fan but I love this one... My advice? Whichever model you go for, get yours out of a diesel or other underpowered application for less high-rpm history.

One noteworthy detail is that BMW-fitted ZFs are supposed to be 'sealed for life'. What the various resources tell you is to disregard that kind of lingo and change the ATF at your own given intervals. Mine's had a torque converter change and one oil change on record and at 360 kkm it's perfect. Good luck, will be keen to read up on your progress...
 
Well first off the result is well worth while. All the modern auto boxes have an overdrive top and this sorts out the P6's refinement and fuel economy at cruise. Just as the LT77/R380 five speed does for the manual cars. Also all the modern auto boxes have at least the top two gears with lock up, which stops the torque convertor slip and makes the box behave like a manual box.

For a handy set of tables as to what production car has which box go to Wikipedia(!!!).

I'm sure if you're that way inclined it must be possible to sort out the bellhousing, spacers, drive plate, torque convertor set up for pretty well any auto box. Certainly people do this sort of thing all the time with manual boxes and I don't see there is anything any more complex for an auto. But I personally don't fancy it when there is a ready made solution available in the ZF HP22/HP24. You need to acquire the front of a Land Rover Discovery/Range Rover/LDV Sherpa HP22 installation. Should be at least one of those lurking every scrapyard worldwide!

For the rest of the box the discussion is more interesting. The HP22 HP24 designation refers to the torque handling capability of the box. As a rough rule of thumb the HP 22 is OK up to about 180HP for a Rover V8. (and note the 4.6 RR used it up to 220hp - I wonder if that's why the warramty claims were up to normal BL standard?) The HP24 is OK up to around the 400hp mark. So if you don't intend going above a carburettored 3.5 a straight HP22 is fine, anything more you ought to think about getting an HP24.

Size wise the HP22 casing goes down the P6 auto tunnel without problem, except that it is very tight near the front firewall. A very slight grind is in order here on some of the casing fins and it also helps to use early S1 engine mounts which drop the engine slightly in the engine bay. The prop shaft needs shortening but that should be easy. You can use the existing rear mounts on a bit of bent steel strip bolted into the tunnel to get them a bit further back.

If you want to use an HP24 things get a bit more complicated. The HP24 casing is bigger and doesn't fit. But the HP24 gear and band cluster (which is where the torque handling comes from) transplants directly into the HP22 casing. So if you're going for a big engine (or want a completely bomb proof transmission) you'll need an XJ40 or BMW HP24 to go with the Land Rover HP22.

To get the 2WD back end you might be lucky and get one automatically (ha ha) with an LDV Sherpa box or you'll need a 2WD HP22. This takes us to a really difficult area. The speedo. It is possible to adapt the speedo drive take off from an LDV box to take a P6 angle drive and standard cable. But there's a bit of machining involved. Or you could have a new cable made up and take it out at right angles through the transmission tunnel and route it via the interior. My current favourite is to use a neat Yank bit of kit that converts a digital output from a toothed wheel on the output flange to prop joint into a little electric motor which drives your manual speedo from the back of the instrument panel. Or you could go fully electronic and get your existing speedo head converted to electronic (possible!! with the existing face!!).

Presuming you would want your box overhauled before you fitted it there is no additional cost from merging all these bits of boxes apart from the cash in hand to the scrapmerchants to source the bits in the first place. Make sure you use a LR valve block - it changes into top earlier!

Next and biggest problem of the lot is how to change gear! I've tried both Range Rover and LDV change levers and they look awfull in a P6. I reckon the Jag arrangement works well visually and parctically. I haven't seen a BMW one in a P6 - I stopped when I got something I liked. Then the $64k question is whether or not to go electronic. Low spec jags aren't, high spec ones are. You can tell by whether or not they have a "Sport" button to the top left of the change lever. To use a Jag electronic directly you have a potential nightmare of disentangling the gearbox control from the engine management from the wiring loom! This is a practical issue before you get to the cerebral issue of does the box do what you want it to!! There are a number of "little black boxes" on sale which claim to allow you to programme the box yourself. This is pretty exciting and well into techy territory. I'm deeply tempted. To give you a flavour, you can play tunes with what speed torque convertor lock up kicks in, in what gear, at what throttle opening and how sharply at what throttle opening. And we haven't even got as far as the gears yet! And you could do yourself a flappy paddle change! The down side is that it sounds like the setting up might take a very long time and if you got it wrong it would be easily possible to burn the box out by telling it to engage two gears at once etc etc. And the ones I've looked at haven't done a ZF yet to use as a start point. These set ups seem to originate in American drag racing where they primarily control GM boxes. There is at least one UK firm advertising a similar system to use on the back of mud racing Land Rovers but I'm not clear whether it's their own system or not. If you did want to go this route you'll need to use a set of electronic internals. So it is actually quite an early decision in the process - you can't easily change routes once you've had the box built.

I think the above pushes you to a non electronic set up unless you are a very focused techy!

Finally the Jag change lever generates a new self build transmission tunnel cover, which shouldn't be too much of a challenge.

Hope all that hasn't put you off. A non electronic set up with a Jag change lever is pretty easy to achieve. Most of the above is about explaining the why's and wherefore's of the options. If you need someone to do it for you, Alan at Classeparts is quite well versed in this and has all the bits on hand. And the result is really well worth the effort.

Chris
 
Chris, that's a very comprehensive breakdown there although I read somewhere that you need to have custom made tubular manifolds to clear the bell housing on the new transmission. Is this the case?
 
Chris, yes let me know about the exhaust, hadn't thought of that.

For speedos I have just acquired a digital one of ebay, sorry to the person that got pipped at the post if you are on here.

These are also available from http://www.caigauge.com there is a reasonable set of installation instructions.
 
It certainly all sounds abit of a mission especially the swapping of gearbox bits from upto 3 units :shock: I thought it would be an easy job for the early box's.
I have been doing a bit of internet search to see what the 6 spd ZF box would need to make it happen and there is not a lot of info on it. I had hoped with the passage of time since it's release that people would have pioneered aftermarket refits but this does not seem to be the case.
I am a reluctant Techie but then a gain I am a design electronics engineer so I could make it happen, if I could get a list of the protocols that the box used I could readily cobble together an nice analogue (no micro's yippee as they P me off)adjustable system but the info is not there and there seems to be no incination from ZF to have this box used out of the approved usage channels.
One of my drivers to change the box is the poor performance that it gives the V8, for an engine that produces aprox 200HP (mine has a webber 500) and only weighs so little it should really have excelent acceleration and it would, if not for the box.
Later boxs ie the zf also have a large weight reduction and manual performance with all the benefits and comforts of the auto. If i also change the cam to something better than factory (ie even a bit of lumpy no 8 wire) I should potentially get about 225 HP and with a weight of less than the factory 1302 kg it will have a very healthy power to weight ratio, not that it's very usable with the standard suspension though the beauty of these conversions is that the fuel consumption will improve along with performance!!!

Graeme
 
Just have to add to this, my post makes me look like a speed junkie lol, when I drive this car it is invariably only at 30 MPH with a big smile on my face as the car burbles along.

Graeme
 
I used a custom made exhaust including the headers/manifolds anyway, as I think the original is far too restrictive. If you were going to use the original manifolds you would still need to have a custom Y piece and centre section made up - but then that would be no different to getting a stainless system. Most manufacturers of stainless systems will want to make and fit to the car. Only additional agro would be having to trailer it to their workshop as you wouldn't have an original system fitted at that stage!

Note also that if you are not going for a huge power output you could use the HP22 internals which symplifies the gearbox sourcing. The mix and match of the gearbox parts would anyway happen at the overhaul workshop - all you need to know is what to ask for!

Chris
 
My concern about any box more complicated than the 4HP22/24 is getting it to fit in the tunnel - I've offered up the 4 speed box to the other car and it will need a certain amount of persuasion to fit in the available space.

From memory the 5 speed and 6 speed ZF boxes are bulkier still so be prepared for some cutting and welding on the tunnel area and maybe a new carpet to fit over the widened tunnel

If you want an ECM for the -24 transmission Compushift make an aftermarket unit <http://www.hgmelectronics.com/products/compushift> also available from Ashcroft
 
Hi folks

Please have a look at the pictures below of my new gearbox.
It is a rebuilt box from a XJ40, with the bellhousing and tail from a ldv, and a pump from ashcroft (the new part). It was a tight fit, bit now it is in the car.

I have an ecm fra compushift, not testet yet.

DPP_0004.jpg

DPP_0007.jpg

DPP_0008.jpg

DPP_0012.jpg

DPP_0013.jpg


Ragnar H.
 
Lookin' good, Ragnar! Is the installation in progress or have you driven it yet? If the former lots of luck, if the latter I await your road test and lots more photos pretty damn keenly! What capacity engine is it attached to, and will you be devising a paddle shifter for the steering wheel? I'm very interested in the benefits of a modern autobox with electronic wizardry listed earlier in this titillating thread. Do those stainless RPi headers fit without having to trim away any metal from the inner chassis rails?
 
mrtask said:
Do those stainless RPi headers fit without having to trim away any metal from the inner chassis rails?
Click to expand...

Do they fit without having to chop away any of the O/S engine mount?
 
Keep us posted. My post is as yet mainly theory - you will be a good couple of steps ahead of me! What solution have you adopted for the speedo drive? I shall also be keen to swop notes on the Compushift.

Chris
 
Hi all

The car is still in progress, after some years. My family is increasing which means that my time for the car is decreasing. But I have the last years built a garage with a pit for the car. Perhaps that will be presented in the "Members project". But I hope to drive the car this summer.
I'll show some pictures after the easter.
I put the engine and gear box in the car a week ago. I still have some welding to do at the rear mounts of the box, but is is almost finished.

Electronic
I bought the Compushift from here, http://www.hgmelectronics.com/products, less expensive than the Norwegian dealer, the price was $1095.00 in the US and £650 in UK (Ashcroft). For the speedo I am to use a product from Abbott, named Cable X http://www.abbott-tach.com/cablex.htm which transforms electronic signals.

Headers
The RPI headers fit without having to trim away any metal from the inner chassis rails, but I needed to chop away some of the rhs engine mount, but on the lhs it was ok.

Engine
I have a wild engine in the car, actually it is a 5,5 litre fra V8developments bought some years ago on ebay. I also have a 4.6 which is on its way to my other car, a NADA needing much work. I had the 4.6 in my first car, but with a little to lumpy camshaft (Piper 285) but I have changed it to Piper RP4.
The 5.5 engine is quite exciting, I have still not started it. In the beginning I am to use carb (Edelbrock) but do want to use injection, perhaps a twin plenum?

I am also upgrading the car, incl. dthe brakes, the diff etc with parts from Classeparts, and Air Conditioning and electric windowlifters.
I hope the car will look original when I am finished.
This is how it looked before the engine was installed a few weeks ago:
DPP_0006.jpg


I'll come back with more after easter, I hope to use some time under the car during the holiday.
 
"The 5.5 engine is quite exciting"
I'll say! That's what I call understatement. Blueman, you've just upped the stakes as regards P6B bragging rights. Crikey, that'll be an absolute stormer, I'm feeling dizzy, think I need to go and have a lie down. What diff will you be using? Hope you have an enjoyable and productive Easter break working on your project, look forward to your next installment.

"Do they fit without having to chop away any of the O/S engine mount?" -
"I needed to chop away some of the rhs engine mount" -
Quattro, you needed to alter the passenger side mount on your RHD car; Ragnar, you needed to alter the driver's side engine mount on your LHD car – correct? Either of you got any photos of what needed to be done and why?
 
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